This Week’s Finds (Week 315)

This is the second and final part of my interview with Thomas Fischbacher. We’re talking about sustainable agriculture, and he was just about to discuss the role of paying attention to flows.

JB: So, tell us about flows.

TF: For natural systems, some of the most important flows are those of energy, water, mineral nutrients, and biomass. Now, while they are physically real, and keep natural systems going, we should remind ourselves that nature by and large does not make high level decisions to orchestrate them. So, flows arise due to processes in nature, but nature ‘works’ without being consciously aware of them. (Still, there are mechanisms such as evolutionary pressure that ensure that the flow networks of natural ecosystems work—those assemblies that were non-viable in the long term did not make it.)

Hence, flows are above everything else a useful conceptual framework—a mental tool devised by us for us—that helps us to make sense of an otherwise extremely complex and confusing natural world. The nice thing about flows is that they reduce complexity by abstracting away details when we do not want to focus on them—such as which particular species are involved in the calcium ion economy, say. Still, they retain a lot of important information, quite unlike some models used by economists that actually guide—or misguide—our present decision-making. They tell us a lot about key processes and longer term behaviour—in particular, if something needs to be corrected.

Sustainability is a complex subject that links to many different aspects of human experience—and of course the non-human world around us. When confronted with such a subject, my approach is to start by asking: ‘what I am most certain about’, and use these key insights as ‘anchors’ that set the scene. Everything else must respect these insights. Occasionally, some surprising new insight forces me to reevaluate some fundamental assumptions, and repaint part of the picture. But that’s life—that’s how we learn.

Very often, I find that those aspects which are both useful to obtain deeper insights and at the same time accessible to us are related to flows.

JB: Can you give an example?

TF: Okay, here’s another puzzle. What is the largest flow of solids induced by civilization?

JB: Umm… maybe the burning of fossil fuels, passing carbon into the atmosphere?

TF: I am by now fairly sure that the answer is: the unintentional export of topsoil from the land into the sea by wind and water erosion, due to agriculture. According to Brady & Weil, around the year 2000, the U.S. annually ‘exported’ about 4×1012 kilograms of topsoil to the sea. That’s roughly three cubic kilometers, taking a reasonable estimate for the density of humus.

JB: Okay. In 2007, the U.S. burnt 1.6 × 1012 kilograms of carbon. So, that’s comparable.

TF: Yes. When I cross check my number combining data from the NRCS on average erosion rates and from the CIA World Factbook on cultivated land area, I get a result that is within the same ballpark, so it seems to make sense. In comparison, total U.S. exports of economic goods in 2005 were 4.89×1011 kilograms: about an order of magnitude less, according to statistics from the Federal Highway Administration.

If we look at present soil degradation rates alone, it is patently clear that we see major changes ahead. In the long term, we just cannot hope to keep on feeding the population using methods that keep on rapidly destroying fertility. So, we pretty much know that something will happen there. (Sounds obvious, but alas, thinking of a number of discussions I had with some economists, I must say that, sadly, it is far from being so.)

What actually will happen mostly depends on how wisely we act. The possibilities range from nuclear war to a mostly smooth swift transition to fertility-building food production systems that also take large amounts of CO2 out of the atmosphere and convert it to soil humus. I am, of course, much in favour of scenarios close to the latter one, but that won’t happen unless we put in some effort—first and foremost, to educate people about how it can be done.

Flow analysis can be an extremely powerful tool for diagnosis, but its utility goes far beyond this. When we design systems, paying attention to how we design the flow networks of energy, water, materials, nutrients, etc., often makes a world of a difference.

Nature is a powerful teacher here: in a forest, there is no ‘waste’, as one system’s output is another system’s input. What else is ‘waste’ but an accumulation of unused output? So, ‘waste’ is an indication of an output mismatch problem. Likewise, if a system’s input is not in the right form, we have to pre-process it, hence do work, hence use energy. Therefore, if a process or system continually requires excessive amounts of energy (as many of our present designs do), this may well be an indication of a design problem—and could be related to an input mismatch.

Also, the flow networks of natural systems usually show both extremely high recycling rates and a lot of multi-functionality, which provides resilience. Every species provides its own portfolio of services to the assembly, which may include pest population control, creating habitat for other species, food, accumulating important nutrients, ‘waste’ transformation, and so on. No element has a single objective, in contrast to how we humans by and large like to engineer our systems. Each important function is covered by more than one element. Quite unlike many of our past approaches, design along such principles can have long-term viability. Nature works. So, we clearly can learn from studying nature’s networks and adopting some principles for our own designs.

Designing for sustainability with, around, and inspired by natural systems is an interesting intellectual challenge, much like solving a jigsaw puzzle. We cannot simultaneously comprehend the totality of all interactions and relations between adjacent pieces as we build it, but we keep on discovering clues by closely studying different aspects: form, colour, pattern. If we are on the right track, and one clue tells us how something should fit, we will discover that other aspects will fit as well. If we made a mistake, we need to apply force to maintain it and hammer other pieces into place—and unless we correct that mistake, we will need ever more brutal interventions to artificially stabilize the problems which are mere consequences of the original mistake. Think using nuclear weapons to seal off spilling oil wells drilled in deep waters needed because we used up all the easily accessible high-quality fuels. One mistake begets another.

There is a reason why jigsaw puzzles ‘work’: they were created that way. There is also a reason why the dance of natural systems ‘works’: coevolution. What happens when we run out of steam to stabilize poor designs (i.e. in an energy crisis)? We, as a society, will be forced to confront our past arrogance and pay close attention to resolving the design mistakes we so far always tried to talk away. That’s something I’d call ‘true progress’.

Actually, it’s quite evident now: many of our ‘problems’ are rather just symptoms of more fundamental problems. But as we do not track these down to the actual root, we keep on expending ever more energy by stacking palliatives on top of one another. Growing corn as a biofuel in a process that both requires a lot of external energy input and keeps on degrading soil fertility is a nice example. Now, if we look closer, we find numerous further, superficially unrelated, problems that should make us ask the question: "Did we assemble this part of the puzzle correctly? Is this approach really such a good idea? What else could we do instead? What other solutions would suggest themselves if we paid attention to the hints given by nature?" But we don’t do that. It’s almost as if we were proud to be thick.

JB: How would designing with flows in mind work?

TF: First, we have to be clear about the boundaries of our domain of influence. Resources will at some point enter our domain of influence and at some point leave it again. This certainly holds for a piece of land on which we would like to implement sustainable food production where one of the most important flows is that of water. But it also holds for a household or village economy, where an important flow through the system is that of purchase power—i.e. money (but in the wider sense). As resources percolate through a system, their utility generally degrades—entropy at work. Water high up in the landscape has more potential uses than water further down. So, we can derive a guiding principle for design: capture resources as early as possible, release them as late as possible, and see that you guide them in such a way that their natural drive to go downhill makes them perform many useful duties in between. Considering water flowing over a piece of land, this would suggest setting up rainwater catchment systems high up in the landscape. This water then can serve many useful purposes: there certainly are agricultural/silvicultural and domestic uses, maybe even aquaculture, potentially small-scale hydropower (say, in the 10-100 watts range), and possibly fire control.

JB: When I was a kid, I used to break lots of things. I guess lots of kids do. But then I started paying attention to why I broke things, and I discovered there were two main reasons. First, I might be distracted: paying attention to one thing while doing another. Second, I might be trying to overcome a problem by force instead of by slowing down and thinking about it. If I was trying to untangle a complicated knot, I might get frustrated and just pull on it… and rip the string.

I think that as a culture we make both these mistakes quite often. It sounds like part of what you’re saying is: "Pay more attention to what’s going on, and when you encounter problems, slow down and think about their origin a bit—don’t just try to bully your way through them."

But the tool of measuring flows is a nice way to organize this thought process. When you first told me about ‘input mismatch problems’ and ‘output mismatch problems’, it came as a real revelation! And I’ve been thinking about them a lot, and I want to keep doing that.

One thing I noticed is that problems tend to come in pairs. When the output of one system doesn’t fit nicely into the input of the next, we see two problems. First, ‘waste’ on the output side. Second, ‘deficiency’ on the input side. Sometimes it’s obvious that these are two aspects of the same problem. But sometimes we fail to see it.

For example, a while ago some ground squirrels chewed a hole in an irrigation pipe in our yard. Of course that’s our punishment for using too much water in a naturally dry environment, but look at the two problems it created. One: big gushers of water shooting out of the hole whenever that irrigation pipe was used, which caused all sort of further problems. Two: not enough water to the plants that system was supposed to be irrigating. Waste on one side, deficiency on the other.

That’s obvious, easy to see, and easy to fix: first plug the hole, then think carefully about why we’re using so much water in the first place. We’d already replaced our lawn with plants that use less water, but maybe we can do better.

But here’s a bigger problem that’s harder to fix. Huge amounts of fertilizer are being used on the cornfields of the midwestern United States. With the agricultural techniques they’re using, there’s a constant deficiency of nitrogen and phosphorus, so it’s supplied artificially. The figures I’ve seen show that about 30% of the energy used in US agriculture goes into making fertilizers. So, it’s been said that we’re ‘eating oil’—though technically, a lot of nitrogen fertilizer is made using natural gas. Anyway: a huge deficiency problem.

On the other hand, where is all this fertilizer going? In the midwestern United States, a lot of it winds up washing down the Mississipi River. And as a result, there are enormous ‘dead zones’ in the Gulf of Mexico. The fertilizer feeds algae, the algae dies and decays, and the decay process takes oxygen out of the water, killing off any life that needs oxygen. These dead zones range from 15 and 18 thousand square kilometers, and they’re in a place that’s one of the prime fishing spots for the US. So: a huge waste problem.

But they’re the same problem!

It reminds me of the old joke about a guy who was trying to button his shirt. "There are two things wrong with this shirt! First, it has an extra button on top. Second, it has an extra buttonhole on bottom!"

TF: Bill Mollison said it in a quite humorous-yet-sarcastic way in this episode of the Global Gardener movie:

• Bill Mollison, Urban permaculture strategies – part 1, YouTube.

While the potential to grow a large amount of calories in cities may be limited, growing fruit and vegetables nevertheless does make sense for multiple reasons. One of them is that many things that previously went into the garbage bin now have a much more appropriate place to go—such as the compost heap. Many urbanites who take up gardening are quite amazed when they realize how much of their household waste actually always ‘wanted’ to end up in a garden.

JB: Indeed. After I bought a compost bin, the amount of trash I threw out dropped dramatically. And instead of feeling vaguely guilty as I threw orange peels into the trash where they’d be mummified in a plastic bag in a landfill, I could feel vaguely virtuous as I watched them gradually turn into soil. It doesn’t take as long as you might think. And it comes as a bit of a revelation at first: "Oh, so that’s how we get soil."

TF: Perhaps the biggest problem I see with a mostly non-gardening society is that people without even the slightest own experience in growing food are expected to make up their mind about very important food-related questions and contribute to the democratic decision making process. Again, I must emphasize that whoever does not consciously invest some effort into getting at least some minimal first hand experience to improve their judgment capabilities will be easy prey for rat-catchers. And by and large, society is not aware of how badly they are lied to when it comes to food.

But back to flows. Every few years or so, I stumble upon a jaw-dropping idea, or a principle, that makes me realize that it is so general and powerful that, really, the limits of what it can be used for are the limits of my imagination and creativity. I recently had such a revelation with the PSLQ integer relation algorithm. Using flows as a mental tool for analysis and design was another such case. All of a sudden, a lot made sense, and could be analyzed with ease.

There always is, of course, the ‘man with a hammer problem’—if you are very fond of a new and shiny hammer, everything will look like a nail. I’ve also heard that expressed as ‘an idea is a very dangerous thing if it is the only one you have’.

So, while keeping this in mind, now that we got an idea about flows in nature, let us ask: "how can we abuse these concepts?" Mathematicians prefer the term ‘abstraction’, but it’s fun either way. So, let’s talk about the flow of money in economies. What is money? Essentially, it is just a book-keeping device invented to keep track of favours owed by society to individuals and vice versa. What function does it have? It works as ‘grease’, facilitating trade.

So, suppose you are a mayor of a small village. One of your important objectives is of course prosperity for your villagers. Your village trades with and hence is linked to an external economy, and just as goods and services are exchanged, so is money. So, at some point, purchase power (in the form of money) enters your domain of influence, and at some point, it will leave it again. What you want it to do is to facilitate many different economic activities—so you want to ensure it circulates within the village as long as possible. You should pay some attention to situations where money accumulates—for everything that accumulates without being put to good use is a form of ‘waste’, hence pollution. So, this naturally leads us to two ideas: (a) What incentives can you find to keep money on circulating within the village? (There are many answers, limited only by creativity.) And (b) what can you do to constrain the outflow? If the outlet is made smaller, system outflow will match inflow at a higher internal pressure, hence a higher level of resource availability within the system.

This leads us to an idea no school will ever tell you about—for pretty much the same reason why no state-run school will ever teach how to plan and successfully conduct a revolution. The road to prosperity is to systematically reduce your ‘Need To Earn’—i.e. the best way to spend money is to set up systems that allow you to keep more money in your pocket. An frequent misconception that keeps on arising when I mention this is that some think this idea would be about austerity. Quite to the contrary. You can make as much money as you want—but one thing you should keep in mind is that if you have that trump card up your sleeve that you could at any time just disconnect from most of the economy and get by with almost no money at all for extended periods of time, you are in a far better position to take risks and grasp exceptional opportunities as they arise as someone would be who committed himself to having to earn a couple of thousand pounds a month.

The problem is not with earning a lot of money. The problem is with being forced to continually make a lot of money. We readily manage to identify this as a key problem of drug addicts, but fail to see the same mechanism at work in mainstream society. A key assumption in economic theory is that exchange is voluntary. But how well is that assumption satisfied in practice if such forces are in place?

Now, what would happen if people started to get serious about investing the money they earn to systematically reduce their need to earn money in the future? Some decisions such as getting a photovoltaic array may have ‘payback times’ in the range of one or two decades, but I consider this ‘payback time’ concept as a self-propagating flawed idea. If something gives me an advantage in terms of depending on less external input now, this reduction of vulnerability also has to be taken into account—’payback times’ do not do that. So—if most people did such things, i.e. made strategic decisions to set up systems so that their essential needs can be satisfied with minimal effort—especially money, this would put a lot of political power back into their hands. A number of self-proclaimed ‘leaders’ certainly don’t like the idea of people being in a position to just ignore their orders. Also note that this would have a funny effect on the GDP—ever heard of ‘imputations’?

JB: No, what are those?

TF: It’s a funny thing, perhaps best explained by an example. If you fully own your own house, then you don’t pay rent. But for the purpose of determining the GDP, you are regarded as paying as much rent to yourself (!) as you would get if you rented out the house. See:

Imputed rent, Wikipedia.

Evidently, if people make a dedicated effort at the household level to become less dependent on the economy by being able to provide most of their essential needs themselves (housing, food, water, energy, etc.) to a much larger extent, this amounts to investing money in order to need less money in the future. If many people did this systematically, it would superficially have a devastating effect on the GDP—but it would bring about a much more resilient (because less dependent) society.

The problem is that the GDP really is not an appropriate measure for progress. But obviously, those who publish these figures know that as well, hence the need to fudge the result with imputations. So, a simple conclusion is: whenever there is an opportunity to invest money in a way that makes you less dependent on the economy in the future, that might be well worth a closer look. Especially if you get the idea that, if many people did this, the state would likely have to come up with other imputations to make the impact on the GDP disappear!

JB: That’s a nice thought. I tend to worry about how the GDP and other economic indicators warp our view of what’s right to do. But you’re saying that if people can get up the nerve to do what’s right, regardless, the economic indicators may just take care of themselves.

TF: We have to remember that sustainability is about systems that are viable in the long run. Environmental sustainability is just one important aspect. But you won’t go on for long doing what you do unless it also has economic long-term viability. Hence, we are dealing with multi-dimensional design constraints. And just as flow network analysis is useful to get an idea about the environmental context, the same holds for the economic context. It’s just that the resources are slightly different ones—money, labour, raw materials, etc. These thoughts can be carried much further, but I find it quite worthwhile to instead look at an example where someone did indeed design a successful system along such principles. In the UK, the first example that would come to my mind is Hill Holt Wood, because the founding director, Nigel Lowthrop, did do so many things right. I have high admiration for his work.

JB: When it comes to design of sustainable systems, you also seem to be a big fan of Bill Mollison and some of the ‘permaculture’ movement that he started. Could you say a bit about that? Why is it important?

TF: The primary reason why permaculture matters is that it has demonstrated some stunning successes with important issues such as land rehabilitation.

‘Permaculture’ means a lot of different things to a lot of different people. Curiously, where I grew up, the term is somewhat known, but mostly associated with an Austrian farmer, not Bill Mollison. And I’ve seen some physicists who first had come into contact with it through David Holmgren‘s book revise their opinions when they later read Mollison. Occasionally, some early adopters did not really understand the scientific aspects of it and tried to link it with some strange personal beliefs of the sort Martin Gardner discussed in Fads and Fallacies in the Name of Science. And so on. So, before we discuss permaculture, I have to point out that one might sometimes have to take a close look to evaluate it. A number of things claiming to be ‘permaculture’ actually are not.

When I started—some time ago—to make a systematic effort to get a useful overview over the structure of our massive sustainability-related problems, a key question to me always was: "what should I do?"—and a key conviction was: "someone must have had some good ideas about all this already." This led me to actually not read some well-known "environmentalist" books many people had read which are devoid of any discussion of our options and potential solutions, but to do a lot of detective work instead.

In doing so, I travelled, talked to a number of people, read a lot of books and manuscripts, did a number of my own experiments, cross-checked things against order-of-magnitude guesstimates, against the research literature, and so on. At one point—I think it was when I took a closer look into the work of the laureates of the ‘Right Livelihood award’ (sometimes called the ‘Alternative Nobel Prize’)—I came across Bill Mollison’s work. And it struck a chord.

Back in the 90s, when mad cow disease was a big topic in Europe, I spent quite some time pondering questions such as: "what’s wrong with the way farming works these days?" I immediately recognized a number of insights I independently had arrived at back then when studying Bill Mollison’s work, and yet, he went so much further—talked about a whole universe of issues I still was mostly unaware of at that time. So, an inner voice said to me: "if you take a close look at what that guy already did, that might save you a lot of time". Now, Mollison did get some things wrong, but I still think taking a close look at what he has to say is a very effective way to get a big picture overview over what we can achieve, and what needs urgent attention. I think it greatly helps (at least to me) that he comes from a scientific background. Before he decided to quit academia in 1978 and work full time on developing permaculture, he was a lecturer at the University of Hobart, Tasmania.

JB: But what actually is ‘permaculture’?

TF: That depends a lot on who you ask, but I like to think about permaculture as if it were an animal. The ‘skeleton’ is a framework with cleverly designed ‘static properties’ that holds the ‘flesh’ together in a way so that it can achieve things. The actual ‘flesh’ is provided by solutions to specific problems with long term viability being a key requirement. But it is more than just a mere semi-amorphous collage of solutions, due to its skeleton. The backbone of this animal is a very simple (deliberately so) yet functional (this is important) core ethics which one could regard as being the least common denominator of values considered as essential across pretty much all cultures. This gives it stability. Other bones that make this animal walk and talk are related to key principles. And these principles are mostly just applied common sense.

For example, it is pretty clear that as non-renewable resources keep on becoming more and more scarce, we will have to seriously ponder the question: what can we grow that can replace them? If our design constraints change, so does our engineering—should (for one reason or another) some particular resource such as steel become much more expensive than it is today, we would of course look into the question whether, say, bamboo may be a viable alternative for some applications. And that is not as exotic an idea as it may sound these days.

So, unquestionably, the true solutions to our problems will be a lot about growing things. But growing things in the way that our current-day agriculture mostly does it seems highly suspicious, as this keeps on destroying soil. So, evidently, we will have to think less along the lines of farming and more along the lines of gardening. Also, we must not fool ourselves about a key issue: most people on this planet are poor, hence for an approach to have wide impact, it must be accessible to the poor. Techniques that revolve around gardening often are.

Next, isn’t waiting for the big (hence, capital intensive) ‘technological miracle fix’ conspicuously similar to the concept of a ‘pie in the sky’? If we had any sense, shouldn’t we consider solving today’s problems with today’s solutions?

If one can distinguish between permaculture as it stands and attempts by some people who are interested in it to re-mold it so that it becomes ‘the permaculture part of permaculture plus Anthroposophy/Alchemy/Biodynamics/Dianetics/Emergy/Manifestation/New Age beliefs/whatever’, there is a lot of common sense in permaculture—the sort of ‘a practical gardener’s common sense’. In this framework, there is a place for both modern scientific methods and ancient tribal wisdom. I hence consider it a healthy antidote to both fanatical worship of ‘the almighty goddess of technological progress’—or any sort of fanatical worship for that matter—as well as to funny superstitious beliefs.

There are some things in the permaculture world, however, where I would love to see some change. For example, it would be great if people who know how to get things done paid more attention to closely keeping records of what they do to solve particular problems and to making these widely accessible. Solutions of the ‘it worked great for a friend of a friend’ sort do us a big disservice. Also, there are a number of ideas that easily get represented in overly simplistic form—such as ‘edge is good’—where one better should retain some healthy skepticism.

JB: Well, I’m going to keep on pressing you: what is permaculture… according to you? Can you list some of the key principles?

TF: That question is much easier to answer. The way I see it, permaculture is a design-oriented approach towards systematically reducing the total effort that has to be expended (in particular, in the long run) in order to keep society going and allow people to live satisfying lives. Here, ‘effort’ includes both work that is done by non-renewable resources (in particular fossil fuels), as well as human labour. So, permaculture is not about returning to pre-industrial agricultural drudgery with an extremely low degree of specialization, but rather about combining modern science with traditional wisdom to find low-effort solutions to essential problems. In that sense, it is quite generic and deals with issues ranging from food production to water supply to energy efficient housing and transport solutions.

To give one specific example: Land management practices that reduce the organic matter content of soils and hence soil fertility are bound to increase the effort needed to produce food in the long run and hence considered a step in the wrong direction. So, a permaculture approach would focus on using strategies that manage to build soil fertility while producing food. There are a number of ways to do that, but a key element is a deep understanding of nature’s soil food web and nutrient cycling processes. For example, permaculture pays great attention to ensuring a healthy soil microflora.

When the objective is to minimize the effort needed to sustain us, it is very important to closely observe those situations where we have to expend energy on a continual basis in order to fight natural processes. When this happens, there is a conflict between our views how things ought to look like and a system trying to demonstrate its own evolution. In some situations, we really want it that way and have to pay the corresponding price. But there are others—quite many of them—where we would be well advised to spend some thought on whether we could make our life easier by ‘going with the flow’. If thistles keep on being a nuisance on some piece of land, we might consider trying to fill this ecological niche by growing some closely related species, say some artichoke. If a meadow needs to be mowed regularly so that it does not turn into a shrub thicket, we would instead consider planting some useful shrubs in that place.

Naturally, permaculture design favours perennial plants in climatic regions where the most stable vegetation would be a forest. But it does not have to be this way. There are high-yielding low-effort (in particular: no-till, no-pesticide) ways to grow grains as well, mostly going back to Masanobu Fukuoka. They have gained some popularity in India, where they are known as ‘Rishi Kheti’—’agriculture of the sages’. Here’s a photo gallery containing some fairly recent pictures:

Raju Titus’s Public Gallery, Picasa.

Wheat growing amid fruit trees: no tillage, no pesticides — Hoghangabad, India

An interesting perspective towards weeds which we usually do not take is: the reason this plant could establish itself here is that it’s filling an unfilled ecological niche.

JB: Actually I’ve heard someone say: "If you have weeds, it means you don’t have enough plants".

TF: Right. So, when I take that weed out, I’d be well advised to take note of nature’s lesson and fill that particular niche with an ecological analog that is more useful. Otherwise, it will quite likely come back and need another intervention.

I would consider this "letting systems demonstrate their own evolution while closely watching what they want to tell us and providing some guidance" the most important principle of permaculture.

Another important principle is the ‘user pays‘ principle. A funny idea that comes up disturbingly often up in discussions of sustainability issues (even if it is not articulated explicitly) is that there are only a limited amount of resources which we keep on using up, and once we are done with that, this would be the end of mankind. Actually, that’s not how the world works.

Take an apple tree, for example. It starts out as a tiny seed, and has to accumulate a massive amount of (nutrient) resources to grow into a mature tree. Yet, once it completes its life cycle, dies down and is consumed by fungi, it leaves the world in a more fertile state than before. Fertility tends to keep growing, because natural systems by and large work according to the principle that any agent that takes something from the natural world will return something of equal or even greater ecosystemic value.

Let me come back to an example I briefly mentioned earlier on. At a very coarse level of detail, grazing cows eat grass and return cow dung. Now, in the intestines of the cow, quite a lot of interesting biochemistry has happened that converted nonprotein nitrogen (say, urea) into much more valuable protein:

• W. D. Gallup, Ruminant nutrition, review of utilization of nonprotein nitrogen in the ruminant, Journal of Agricultural and Food Chemistry 4 (1956), 625-627.

A completely different example: nutrient accumulators such as comfrey act as powerful pumps that draw up mineral nutrients from the subsoil, where they would be otherwise inaccessible, and make them available for ecosystemic cycling.

Russian comfrey, Symphytum x uplandicum

It is indeed possible to not only use this concept for garden management, but as a fundamental principle to run a sustainable economy. At the small scale (businesses), its viability has been demonstrated, but unfortunately this aspect of permaculture has not received as much attention yet as it should. Here, the key questions are along the lines of: do you need a washing machine, or is your actual need better matched by the description ‘access to some laundry service’?

Concerning energy and material flows, an important principle is "be aware of the boundaries of your domain of influence, capture them as early as you can, release them as late as you can, and extract as much beneficial use out of them as possible in between". We already talked about that. In the era of cheap labour from fossil fuels, it is often a very good idea to use big earthworking machinery to slightly adjust the topography of the landscape in order to capture and make better use of rainwater. Done right, such water harvesting earthworks can last many hundreds of years, and pay back the effort needed to create them many times over in terms of enhanced biological productivity. If this were implemented on a broad scale, not just by a small percentage of farmers, this could add significantly to flood protection as well. I am fairly confident that we will be doing this a lot in the 21st century, as the climate gets more erratic and we face both more extreme rainfall events (note that saturation water vapour pressure increases by about 7% for every Kelvin of temperature increase) as well as longer droughts. It would be smart to start with this now, rather than when high quality fuels are much more expensive. It would have been even smarter to start with this 20 years ago.

A further important principle is to create stability through a high degree of network connectivity. We’ve also briefly talked about that already. In ecosystem design, this means to ensure that every important ecosystemic function is provided by more than one element (read: species), while every species provides multiple functions to the assembly. So, if something goes wrong with one element, there are other stabilizing forces in place. The mental picture which I like to use here is that of a stellar cluster: If we put a small number of stars next to one another, the system will undergo fairly complicated dynamics and eventually separate: in some three-star encounters, two stars will enter a very close orbit, while the third receives enough energy to go over escape velocity. If we lump together a large number of stars, their dynamics will thermalize and make it much more difficult for an individual star to obtain enough energy to leave the cluster—and keep it for a sufficiently long time to actually do so. Of course, individual stars do ‘boil off’, but the entire system does not fall apart as fast as just a few stars would.

There are various philosophies how to best approach weaving an ecosystemic net, ranging from ‘ecosystem mimicry‘;—i.e. taking wild nature and substituting some species with ecological analogs that are more useful to us—to ‘total synthesis of a species assembly’, i.e. combining species which in theory should grow well together due to their ecological characteristics, even though they might never have done so in nature.

JB: Cool. You’ve given me quite a lot to think about. Finally, could you also leave me with a few good books to read on permaculture?

TF: It depends on what you want to focus on. Concerning a practical hands-on introduction, this is probably the most evolved text:

• Bill Mollison, Introduction to Permaculture, Tagari Publications, Tasmania, 1997.

If you want more theory but are fine with a less refined piece of work, then this is quite useful:

• Bill Mollison, Permaculture – A Designer’s Manual, Tagari Publications, Tasmania, 1988.

Concerning temperate climates—in particular, Europe—this is a well researched piece of work that almost could be used as a college textbook:

• Patrick Whitefield, The Earth Care Manual: a Permaculture Handbook for Britain and Other Temperate Climates, Permanent Publications, East Meon, 2004.

For Europeans, this would probably be my first recommendation.

JB: Thanks! It’s been a very thought-provoking interview.

Ecologists never apply good ecology to their gardens. Architects never understand the transmission of heat in buildings. And physicists live in houses with demented energy systems. It’s curious that we never apply what we know to how we actually live.Bill Mollison

80 Responses to This Week’s Finds (Week 315)

  1. Florifulgurator says:

    Great interview! Stuff that’s on my mind and I’m trying to tell people. Flows and cycles – it’s amazing how stupid our civilization can be. (Just examine your sanitation system.) It seems the best “technology” to solve the climate problem would be serious agriculture. The stupid and destruction happening in “current” agro industry is amazing. (A German agriculturalist of the 1920s already noted, “they heat the sky and manure the oceans”…)

    Which reminds me of The One Best Thing Everyone Could Do to Slow Climate Change: Pee outside!

    The Austrian permaculture icon is Sepp Holzer. He’s done amazing things like growing citrus in the Austrian mountains.

    I’m quite curious what Thomas thinks about biochar…

    — Martin Gisser

  2. Thomas Fischbacher says:

    Actually, Holzer is quite controversial. While he seemingly has had a number of remarkable successes, some of his former clients are seriously angry about his work – in particular, one major charge is that he planned earthworks for clients, having neither the necessary expertise, nor having taken out insurance, so when they failed, clients ended up sitting on quite a pile of debt.

    I have not looked into the details of this issue, but at least Holzer and clients do agree that there were failed earthworks – and I would say that this then certainly is mostly the fault of the person who did the engineering design.

    Biochar – it’s just one of many tools in the toolbox. Not a miracle cure, but probably quite appropriate in some situations.

  3. Darin says:

    I don’t think households becoming more independent would have a devastating effect on GDP. It would if those households took the money they didn’t spend on whatever they spent it on before and used it for kindling, but as long as they still spent it at the same rates there shouldn’t be a change in GDP, just a change in the composition of the economy.

    If I fix my own stuff and generate my own electricity, then use the money I would have spent on those items in the past to buy Fabergé eggs, there would be fewer people employed fixing stuff for me, building new items to replace the broken ones, or maintaining all the stuff that generates electricity from the grid, but there would also be a greater number of people making Fabergé eggs and stuff for off-grid electricity. As long as I don’t destroy any of the money that flowed through me GDP should remain the same. I’m pretty sure GDP is process agnostic and flows just like processes in nature.

    • Thomas Fischbacher says:

      Well… if all your needs are covered – why should you sell as much of your time by going to work as you did beforehand, if you alternatively also could e.g. spend it with your children instead?

      • Darin says:

        If all your needs were covered and you wanted to spend more time with your children you would probably be doing that in the first place, and there probably wouldn’t be much in the way of change.

        If as you implied, people on a massive level changed their lifestyles such that they didn’t require input from whatever portions of the economy and also decided they didn’t want to work anymore, which is possible but not likely, there would be a drop in GDP in that context, and it would be accompanied by a rise in NDP as the depreciation rate declined from people doing their own stuff. Either way NDP would remain about the same, and I doubt anyone, even an economist ;), would call that a devastating change.

        • Darin says:

          I should say work as much, since even the most enterprising DIY’er has limits to what they can do and would still need to work to raise capital for stuff they couldn’t fix/fabricate at home.

  4. Allan Erskine says:

    Great interview! Within 10 minutes of reading, I’d found these guys (searching for ‘permaculture’ on

    The domains or are up for grabs!

  5. John Baez says:

    Thomas wrote:

    A further important principle is to create stability through a high degree of network connectivity. We’ve also briefly talked about that already. In ecosystem design, this means to ensure that every important ecosystemic function is provided by more than one element (read: species), while every species provides multiple functions to the assembly. So, if something goes wrong with one element, there are other stabilizing forces in place.

    It’s worth noting that there’s a big controversy in ecology over whether—or when—highly connected networks are stable. I wrote about this on

    Systems ecology, Azimuth Library.

    Here’s what I said:

    An interesting question in systems ecology is: which factors make a food web stable or unstable? For decades there has been an intense debate on this question, beginning with quite crude models and moving to ever more realistic ones, and also featuring ever more careful experiments. An excellent review article, featuring a large bibliography, is:

    • Louis-Félix Bersier, A history of the study of ecological networks, in Biological Networks, ed. Francois Képès, World Scientific, Singapore, 2007.

    Many consider the father of food-web ecology to be Charles Elton, who in the 1920s noted the ‘pyramid of numbers’ and other basic features of food webs. Elton noted that some simple two-species predator-prey models are unstable and argued that complex food webs were more stable. This became an article of faith in ecology. In 1942, R. L. Lindeman focused attention on the flow of energy through food webs. In the early 1970s, R. M. May showed that in some models, food webs became less stable as the number and strength of species interactions increased:

    • R. M. May, Stability and Complexity of Model Ecosystems, 2nd edition, Princeton U. Press, Princeton, New Jersey, 1974.

    This led to an outburst of work seeking to show that May’s results were based on oversimplifications, e.g. assuming that any given species has an equal probability of interacting with any other. In the later 1970s, J. E. Cohen began investigating the topology of food webs:

    • J. E. Cohen, Food Webs and Niche Space, Princeton U. Press, Princeton, New Jersey, 1978.

    Here is a more recent article in this line of work:

    • Phillip P. A. Staniczenko, Owen T. Lewis, Nick S. Jones and Felix Reed-Tsochas, Structural dynamics and robustness of food webs, Ecology Letters 13 (2010), 891-899.

    Abstract: Food web structure plays an important role when determining robustness to cascading secondary extinctions. However, existing food web models do not take into account likely changes in trophic interactions (‘rewiring’) following species loss. We investigated structural dynamics in 12 empirically documented food webs by simulating primary species loss using three realistic removal criteria, and measured robustness in terms of subsequent secondary extinctions. In our model, novel trophic interactions can be established between predators and food items not previously consumed following the loss of competing predator species. By considering the increase in robustness conferred through rewiring, we identify a new category of species–overlap species–which promote robustness as shown by comparing simulations incorporating structural dynamics to those with static topologies. The fraction of overlap species in a food web is highly correlated with this increase in robustness; whereas species richness and connectance are uncorrelated with increased robustness. Our findings underline the importance of compensatory mechanisms that may buffer ecosystems against environmental change, and highlight the likely role of particular species that are expected to facilitate this buffering.

    Felix Reed-Tsochas is the head of the Complex Agent-Based Dynamic Networks (or ‘CABDyn’) group at the University of Oxford:

    CABDyn Complexity Centre.

    • Thomas Fischbacher says:

      Yes, that’s absolutely right – I also cover this in my “mathematics for complex systems” lecture. Here, however, I have something much simpler and much more immediate in mind: It makes a world of a difference, for example, whether you grow things in a way that makes it extremely difficult for the fungi in the soil to live or not. If you kill the fungi, then much of the inner mechanics of the system will not work any longer, from nutrient retention to glomalin production. As long as there is habitat for soil fungi, something will come and colonize the plot and provide a number of important functions. It would, however, be mistaken to believe that the species composition would tend to a stable equilibrium.

      Funnily, ecology in a certain sense has a didactic problem here which is kind-of just the opposite as the one in physics. Many people have difficulties understanding Lagrangian mechanics because it is in a way based on a “teleological” principle: rather than asking “what happens next” as in Newtonian mechanics, one asks “how do we get there”? In ecology, the problem is that one often has a (questionable) concept of succession endpoint (a “climax state”) in mind and asks for the path by which succession would take one there when it would be much more appropriate to instead use Newtonian thinking and ask: how does this disturbance right now (fire, species introduction, etc.) change the system? As John mentioned in the beginning of the interview, European forests are in a sense still recovering from the last ice age – how can one talk of a stable succession endpoint with self-balancing species composition in such a situation?

      Incidentally, there is a nice discussion of this point towards the end of Dave Jacke’s and Eric Toensmeier’s book “Edible Forest Gardens”.

      • Thomas Fischbacher says:

        Hm, I just remembered a passage from one of Masanobu Fukuoka’s books (“The One Straw Revolution”). Fukuoka studied microbiology and during World War 2 worked for the Japanese Ministry of Agriculture where he increasingly started to question whether there was any common sense to the way he saw people (mis-)apply “the scientific method”.

        Specialists in various fields gather together and observe a stalk of rice. The insect disease specialist sees only insect damage, the specialist in plant nutrition considers only the plant’s vigor. This is unavoidable as things are now.

        As an example, I told the gentleman from the research station when he was investigating the relation between rice leaf-hoppers and spiders in my fields, “Professor, since you are researching spiders, you are interested in only one among the many natural predators of the leaf-hopper. This year spiders appeared in great numbers, but last year it was toads. Before that, it was frogs that predominated. There are countless variations.”

        A simple gardener’s observation that very clearly shows the difference between “stability (of species composition) against small perturbations” and “resilience against catastrophic failure” (here, major pest outbreaks).

        • Tim van Beek says:

          15 years ago I attended an introductory lecture in medicine at the university hospital in Göttingen; an old lady in a wheelchair was pushed onto the stage and the professor said:

          As an example in differential diagnosis: We don’t know yet what illness she has. There is an expert in illness A who thinks it could be illness A. On the first floor we have an expert in illness B who thinks it could be illness B. And then there is professor Mayer who is a specialist in illness C, he thinks it could be illness C.

          (I’m not making this up; I studied medicine for a year to find out if this could turn out to be a career option).
          Next he said (towards the audience):

          Anyway, I’m quite interested in this problem and what will turn out to be the solution.

          To which the lady in the wheelchair – ignored so far – added:

          Yes, er, I’m interested in it, too.

    • Graham says:

      It is possible to have an ecosystem of one species:

  6. John Baez says:

    I wish you and Florifulgurator would engage in a bit more discussion of biochar. Flori thinks it’s vitally important as a way to remove CO2 from the atmosphere, while for you it’s “just one of many tools in the toolbox”. Perhaps it’s because he’s more concerned about global warming? I should have asked you about global warming; doesn’t this crisis call for emergency action above and beyond what permaculture typically involves?

  7. Thomas Fischbacher says:

    Let me be clear about this: our best chance to take CO2 out of the atmosphere very likely is by putting it back into the soil. But there also are other ways to do that than the presently hyped biochar. Biochar may be useful in some situations, but one has to remember a few things here. For example, it has a fairly high ash content, giving it quite a high pH. You would not want to blindly apply that to soils wherever you can. Also, due to its high surface area, it may end up binding nutrients where you do not want it to.

    Part of the problem is again the human perspective. When we think about plant growth, our perception generally is too strongly fixed on what is going on above the ground. Quite often, it is much more interesting to see what is going on in the soil. I think the discussion of biochar to some extent reflects that bias – grow something, take the aboveground plant material, do something to it, and put it into the soil.

    Now, how about instead tweaking the process by which plants put organic matter into the soil in the first place? Note that under normal conditions quite a lot of the carbon fixed in photosynthesis goes into the soil (say 1/3) to feed the soil life, in particular the fungi and other microflora that does very useful work for green plants. Can we use this to our advantage to build soil humus? A number of permaculture practitioners are experimenting with a method that involves deliberately growing “weedy” pioneer species, hard pruning them at certain times to (a) use the aboveground biomass for mulch, e.g. to bring more degraded soil back to fertility, and (b) induce root self pruning (as the plant tries to maintain a certain root:shoot ratio) which will increase the organic matter content in the soil.

    There are a number of variations on this theme – one can do it with grasses, herbs, shrubs, trees, using animals or not, etc. There certainly is a lot of land that would desperately need such fertility-building, and in the process, this would take quite some carbon out of the atmosphere. But somehow that’s not as sexy as the biochar idea – maybe because we are too strongly fixed on the idea of needing to invent/engineer something new. The method described above can be employed even using just hand tools.

    An interesting approach has been suggested by P.A. Yeomans – this may well need some more research to assess whether Yeomans’ very positive description of the method is adequate.

    • Right. It is dangerous to sell biochar as a miracle cure. (Just look at other sloppy abuses of miracle tech.) It needs intelligence (wisdom) and care – something the industrial consumer hominid wants to avoid at all cost. Just throwing char on your field would be a bad thing. It needs to be “activated” first: Activating the water absorbency and feeding it with nutrients.

      Recently an organic farmer told me about an amazing number (but I forgot meanwhile and haven’t checked) about the little percentage of humus we would need to add to global agricultural land to absorb all our excess CO2. (I bet Thomas knows that number.)

      But there’s a problem: How stable would that humus be against climate change? What about the next generation farmer who might just deplete it again? Biochar promises to be a safer carbon storage. Plus, you can get almost 50% of soil carbon content. And it is a faster method. We have no more time to lose.

      Of course biochar does not liberate the farmer from caring about soil life. (Soil life! It’s a breathtakingly complex and beautiful area of study. Forget about the cosmos – the galaxies and super novae etc. etc. are boring and unglamorous compared to a handful of good dirt.)

      Thomas’ quote of Fukuoka reminds me of Sir Albert Howard’s An Agricultural Testament (1943), where he has similar criticism of agricultural science and math. This book is an amazing read and still relevant.

      — Martin Gisser

      • Thomas Fischbacher says:

        I think there is a flaw in this logic:

        1. Via biochar, we can straightaway go to 50% soil carbon.

        2. The advantage of biochar over building topsoil is that, hypothetically, future farmers may just deplete topsoil again, while biochar is chemically more stable.

        If you have anything around that is 50% elemental carbon, that’s pretty much a fuel, so, hypothetically, future generations may just use it as such.

        So, in order to strongly favour biochar over other methods that put carbon into the soil, there has to be a better reason than such a hypothetical scenario.

    • Thomas wrote:

      For example, it has a fairly high ash content, giving it quite a high pH

      I just checked my secret extreme biochar extreme compost bin hidden behind my parents’ garden house. The pH varies from below 3.5 to 8, measured with a passive-electric device poked into the bucket. Mixed samples soaked with tap water equilibrated at 3.5, 5, and 7. That water tested with pH test strips gave a pH of 8. The most conclusive indicator seems the worms: I is teeming with Enchytraeus whiteworms (the ersatz earthworms of bogs and forests), which indicates slightly acidic soil.

      The compost is a mixture of 1) worm compost (worms collected last fall from varying depth in my parents’ conventional garden) which I kept with ca. 50% charred wood pellets (pre-soaked in urine) over winter in the cellar and 2) bokasi compost with ca. 50% charred pellets pre-soaked with bokashi seepage fluid (details on pellet charring, my simplified bokashi bucket and pH readings see here). The worm compost got some amount of ashes and burnt lime sands from a permanent camp fireplace at a Swiss mountain river. pH in winter was ca. 7. The bokashi got first mixed with a little soil in early spring and kept in an aerated bucket for a month (first it developed green mildew which vanished quickly after addition of some pure char).

      Both composts were then mixed in April. The old-bokashi smell was an olfactory inferno. It is still noticeable (while the humanure from the worm compost is no longer detectable)…

      Now, the earthworm population hasn’t increased, but at least they produced some offspring. Instead it’s now an enchytraeus paradise.


      P.S.1. I’m not sure if bokashi compost is as good as it is hyped.
      P.S.2. In winter I got a crazy idea of some “green maths” research: Hibernating earthworms tie themselves in knots. Prime knots?

  8. Graham says:

    The author Colin Tudge has written two books in this general area: ‘Feeding People is Easy’, and ‘Good Food for Everyone Forever’. I haven’t read them, but I have read, and highly recommend, his ‘The Variety of Life: A Survey and a Celebration of All the Creatures That Have Ever Lived’.

  9. The 50% is just an estimate from my current experiments with “extreme biochar“. The other 50% are compost(s) and sand. Plus, large doses of urine during production. Numbers from Lehmann are about 30% max. char.

    Alas I’ve left my garden behind and just kept a few pots which are now in my parents’ garden. The malva alcea in one of these pots is not as big as those growing right next to the compost, but the difference isn’t that big. I’ll do 2 photos soon for the Azimuth Project page Experiments in biochar.

    I don’t know how aged/depleted biochar soil will be like. That’s one reason to experiment with it now. As I said, biochar is no excuse to forget about good soil practise. I strongly suspect that with biochar you get more resilient humus: The pores of the char (well-burnt out char like in the above page) are a refuge for microbial life, particularly mycorrhizal funghi.

    This is a subject of current research. From this note:

    The really big discovery is that glomalin is 30 to 40 percent Carbon which is stored in soil for up to 42 years. A major component of soil organic matter, glomalin accounts for 27 percent of Carbon in soil. The U.S. Department of Energy is currently funding studies to determine glomalin’s promising potential to offset atmospheric CO2.


    Researchers believe that biochar contributes to pro-mycorrhizal soil environments via multiple mechanisms:

    * Biochar appears to modify soil pH, CEC and water holding capacity toward a more favorable environment for mycorrhizal colonization and activity.
    * Biochar seems to promote microbial populations, further stimulating mycorrhizal performance.
    * Biochar may favorably influence the complex chemical communications between plants and mycorrhizae and may vitiate certain inhibitory compounds.
    * Biochar’s myriad, tiny pores may serve as physical “shelters” for mycorrhizal hyphae and various symbiotic bacteria, protecting them from microbial predators.

    Most studies indicate that mycorrhizae and their associated plants grown in biochar-treated soils significantly out-perform non-biochar controls.

  10. John Baez says:

    Here’s a bit of the interview I didn’t include but seems worth adding here. Maybe I’ll even go ahead and add it to the main article:

    JB: For example, a while ago some ground squirrels chewed a hole in an irrigation pipe in our yard. Of course that’s our punishment for using too much water in a naturally dry environment, but look at the two problems it created. One: big gushers of water shooting out of the hole whenever that irrigation pipe was used, which caused all sort of further problems. Two: not enough water to the plants that system was supposed to be irrigating. Waste on one side, deficiency on the other.

    That’s obvious, easy to see, and easy to fix: first plug the hole, then think carefully about why we’re using so much water in the first place. We’d already replaced our lawn with plants that use less water, but maybe we can do better.

    TF: Well, let’s see. You live in a place in California with an annual average precipitation of about 380 millimeters — in very wet years, more than twice as much, and in dry years, less than a quarter of that. That means that a 100 square meters roof would on average collect about 40 cubic meters of water annually. A ballpark figure for household water use in California is about 600 liters/person/day,according to:

    which would mean about 220 cubic meters per person annually. (Note that we Germans use about 200 liters/person/day.) That gives us a rough idea for the amount of water that’s flowing through Californian households. As one can grow a kilogram of wheat using about 1000 liters of water, we are talking about the equivalent of 200 kilograms of wheat. At about 3000 calories per kilogram, that water could effectively become a sizable contribution to one’s diet.

    So… let’s take another look at this “catch resources as early they enter your domain of influence and release them late” issue. If you did just the opposite of xeriscaping, i.e. modified the flows a bit so that you use the greywater to grow e.g. fruit and nut trees (makes more sense than grain in a number of ways here), and in that way grew a certain part of your calories yourself, then that not only reduces your economic dependency to buy in food, but it also reduces the amount of additional water needed in agriculture to feed you.

    If you want to see how this could look like in practice, this video might give you a reasonable idea:

    JB: I hope my wife and I don’t each use 600 liters of water a day, three times as much as the average German! We replaced our lawn with xeriscaping and fruit trees to help reduce water usage and get some nice fruit. But I’ll have to check our water bills when we get back to Riverside, and estimate our total consumption.

    Unfortunately we don’t use greywater for watering our yard; I’m not particularly good at home improvements, or even getting other people to do them for me. But it’s an appealing idea. It used to be illegal in California to use greywater for watering plants, but they changed that law:

    • Tim van Beek says:

      Germans have invested in saving water for quite some time now, to an extend that starts to hurt the infrastructure (clogging of the drainage systems etc.). On the other hand you don’t need to water anything, usually, because there is almost always enough rain.

      • Thomas Fischbacher says:

        Even in Germany it’s not that straightforward. Munich may have about 1100 millimeters of anual precipitation (wetter than Southampton at about 800 millimeters), but Potsdam typically gets only about 500. That’s not as dry as California, but it’s not that far away either.

        Summers can be quite arid in Brandenburg.

        • Tim van Beek says:

          Okay :-) But isn’t the area of Brandenburg traditionally called Germany’s sandbox or something similar, anyway?

  11. nad says:

    Yes because it contains Das Kapital called the Berlin.

  12. Thomas Larsson says:

    Last weekend we found that some potatoes were growing roots (?), so I decided to plant them at our summer house. I have never cared much about gardening before, but my grandfather used to grow and sell potatoes on a small scale, so I have some vague idea how it should be done. A learning experience, at least.

    One thing keeps me worried though. How many people can sustainable agriculture sustain?

    • Frederik De Roo says:

      It matters whether you’re considering staple crops or just vegetables. I have no precise number in mind, but I strongly suppose it’s certainly smaller for staple crops. For vegetables I’ve read claims it’s certainly not worse. However, current industrial agriculture is not sustainable, so it’s a bit dishonest to compare the current number time-dependent phenomenon with the sustainable number, if you’re considering a longer timescale.

      As far as I know, permaculture is mainly applied to growing vegetables etc, while most of our calories come from the annual staple crops wheat, rice, potatoes and soy. To cultivate those in a sustainable manner is very labor-intense (perhaps besides the example of the rice provided somewhere above, I hope there are other examples I’m not aware of). But I’ve read there are ideas for using nuts as a staple crop and growing nut trees in a sustainable manner.

      • Thomas Fischbacher says:

        Ad “As far as I know, permaculture is mainly applied to growing vegetables etc, ” — this is a common misconception. The root of the problem is that quite some people try to fit permaculture into some (too narrow) framework they know and mistake it for a gardening technique. It’s much more than that. And, it in fact does have a number of things to say about growing calories and protein. And staying warm in winter. And having a reliable water supply. And a resilient society.

    • One thing keeps me worried though. How many people can sustainable agriculture sustain?

      My worry, too. We should collect some numbers at the Azimuth Project. In this article Richard Dahl quotes

      * David Pimentel (200?) – 2 billion
      * a classic economist (1995) – unlimited
      * Paul Ehrlich (1971) – 0.5 billion

      James Lovelock says (Revenge of Gaia 2006) we should stabilize at 0.5-1 billion. Somewhere I read we currently produce enough food to feed 20 billion (FAO 200?)…

      Given that the biosphere already starts shrinking (plant and phytoplankton productivity declining), an optimist guess would be 1 billion (if we learn to behave and the overshoot population vanishes peacefully within the next decades). This is beyond worrisome…

    • Thomas Fischbacher says:

      Concerning this “at most 0.5/1/2/ billion people” issue, I strongly get the idea that this is more about religious ideology than it is about science. There are many assumptions entering these numbers, and coming up with a number without ever mentioning any of these assumptions is, in my view, highly questionable.

      Note also that the question about “how many people sustainable agriculture can feed” is quite misleading. The problem is that this topic easily gets very emotional, and as soon as emotions are involved, many people’s otherwise sound reasoning abilities just shut off.

    • The problem with religious ideology (incl. certain economists) is that a population ceiling is usually denied (i.e. the planet is assumed a flat or hyperbolic noncompact space).

      I don’t think there’s much ideology behind Pimentel, Ehrlich, or Lovelock. (They might of ourse inform ideologues.) This article by Sergey Kapitza (2006) suggests 10-12 billion and contains a larger table of estimates (p. 177), some suggesting 30 billion. (Somehow I doubt this and find 1-3 billion the most plausible.)

      • I just got an idea of how to easily get a plausible number of human carrying capacity… (But I’m currently sitting at lots of work and will get home late, so…)

        In Sir Albert Howard’s book I mentioned above there are numbers of people per acre which the Chinese managed to sustain for millenia. Another interesting number would be of Japan during the Edo period. Look up total agricultural land today. Compute. The result is for a pre-industrial civilization with wise soil management and no global warming. (Methinks a very optimistic number – a theoretical upper limit.)

        • Thomas Fischbacher says:

          Okay, let’s do that for the sake of the exercise – but as I say, I consider this as nonsense.

          But let us look not at Albert Howard’s book, but at Franklin Hiram King’s book “Farmers of Forty Centuries” instead (because I am somewhat more familiar with that). King was sort-of the founder of soil physics and I think he also invented the round silo. Close to his death, he undertook a journey to asia to study farming methods there. The text of his book is also available on Project Gutenberg – quite an interesting book, by the way. One passage I remember is (cf.

          The three main islands of Japan in 1907 had a population of 46,977,003 maintained on 20,000 square miles of cultivated field. This is at the rate of more than three people to each acre, and of 2,349 to each square mile; and yet the total agricultural imports into Japan in 1907 exceeded the agricultural exports by less than one dollar per capita. If the cultivated land of Holland is estimated at but one-third of her total area, the density of her population in 1905 was, on this basis, less than one-third that of Japan in her three main islands. At the same time Japan is feeding 69 horses and 56 cattle, nearly all laboring animals, to each square mile of cultivated field, while we were feeding in 1900 but 30 horses and mules per same area, these being our laboring animals.

          So we are talking about roughly 1100 square meters per person. Now, Earth has a surface area of 510 million square kilometers. 29% of this are land, and 10% of that (according to the CIA World Factbook) are arable land. So, we are using about 3% of Earth’s surface area to feed the human population. That’s 1.5*10^13 square meters, which then translates to 14 billion people.

          Note that there also is quite some land around which is not used for producing food because we ruined it in the past. That may easily be another 3% of Earth’s surface area. Let us say we get a serious rehabilitation effort going and manage to bring that back to life. That would then give us 28 billion people.

          I believe neither of these numbers – but nevertheless, what is quite clear is that it is all about whether we make a conscious effort to repair damaged land.

          Concerning large scale land rehabilitation, this video may be interesting – we are talking about an area roughly the size of Belgium here (if I remember right):

        • Great. Howard actually cited King. I would stick to 14 billion. What isn’t factored in is the diverse climatic conditions. With that methinks the result isn’t that nonsensical but quite palpable.

          — Martin Gisser

        • The Loess Plateau videos are fascinating and heartening. Thanks! So much for “Farmers of Forty Centuries”…

      • Thomas Fischbacher says:

        No religious ideology behind Ehrlich? Have you ever had a look at his book “The Population Bomb”? I think it might be possible that he is right with his estimates (I won’t exclude that), but if you take a close look at this publication, you will find that:

        (a) He gives little if any reasoning explaining how he arrives at his numbers.

        (b) At the end of the book, he gives fairly detailed instructions for how to become a missionary, and how to deal with certain groups of people.

        There’s about as much religious ideology in what Ehrlich writes as in the writings of another Stanford Professor who has written quite a lot on his private web page on sustainability, John McCarthy. Now, I like some of McCarthy’s other work quite a lot – LISP is one of the most powerful tools I have in my theoretical physicist’s toolbox. But what he has written about “the sustainability of human progress” is easily identified as quite flawed in many ways.

        The human population is the one issue where I’ve come to the conclusion that pretty much no one really has a clue, but that does not stop a lot of people from writing about it as if they had.

        Let me pose it as a challenge then: can you come up with a plausible Fermi calculation that gives us an idea about what a sustainable human population level would be?

        As I say, I like to analyze issues starting from those aspects where I can get some insights I can be fairly certain about. If anyone knows of a sound approach to the question of how high the planetary human carrying capacity probably is, please, by all means, give me a reference.

        Specifically, the big question that easily changes any result by quite likely at least a factor four is: what assumptions does one make about the behaviour of the population? Is the key assumption one of nature having to be able to absorb the fertility-destroying impact of the human population? Can we imagine a fertility-building society?

      • Darin says:

        Do you have any specific economists and statements in mind? Just about every introductory econ text starts out with the definition of economics being roughly how finite time and resources are spent. I have a feeling that any statements about unlimited anything from economists are either taken out of context or are deliberate plays for attention of some sort.

        At the same time we need to take into account the context of what we’re citing. Ehrlich for instance, if I’m recalling this accurately, was assuming a global average lifestyle equivalent to the impact of someone in the 1970s United States for everyone on the planet. In retrospect it’s easy to say that isn’t accurate because even present day Americans aren’t using what 1970s Americans were in terms of energy and causing the same externalities, but at the time it wasn’t something inconceivable at the time, just something on the high side. I’m not sure what Pimental’s assumptions were, but like Thomas said, we need to take everything with a grain of salt.

        It’s kinda like responding with just a number if someone asks you what kind of mileage equivalence your car/bike/etc gets. You may state some figure, and include one unit, but without the per L, gal, 100km, or whatever the complementary unit/s are, it doesn’t provide enough information to draw any conclusions. The same applies to carrying capacity estimates. Without some metric we can compare to the current global average lifestyle and population it’s hard to tell if an estimate is realistic.

        P.S. Feel free to remind me to post some sources. I don’t have time atm, but I should be able to get around to them later this weekend if anyone is interested.

        • Darin,

          My favorite economist is Larry Summers, who said in 1991 (then World Bank’s chief economist):

          There are no … limits to the carrying capacity of the earth that are likely to bind any time in the foreseeable future. There isn’t a risk of an apocalypse due to global warming or anything else. The idea that we should put limits on growth because of some natural limit, is a profound error…

          Regarding carrying capacity numbers, I note we haven’t made it much explicit that they always rely on diverse conditions. (E.g. iron age vs. bronze age vs. stone age, etc.,. vegetarian diet or not, ocean protein supplement, etc. etc.). That’s why I liked the 14 billion number, where the condition is quite explicit (c19th Japanese civilization). Alas, the planet is not Japan and the numbers are much more fuzzy. E.g. arable land (13,805,153 km²) vs. agricultural land (48,836,976 km²).

          Meanwhile I came across a number of England in A.D. 1089 from William the Conqueror’s Domesday Book – it is a shocking 22 acre per person. That would give a world carrying capacity of just 550 million (if the 22 acre are counted as agricultural land).

          — Martin Gisser

        • John Baez says:

          Darin wrote:

          I have a feeling that any statements about unlimited anything from economists are either taken out of context or are deliberate plays for attention of some sort.

          I suppose you could say Larry Summers (quoted above by Martin) was making a “deliberate play for attention”… but are you saying he didn’t really believe what he said?

          Or how about these remarks by Julian Simon, the famous opponent of Paul Ehrlich:

          “Our supplies of natural resources are not finite in any economic sense. Nor does past experience give reason to expect natural resources to become more scarce. Rather, if history is any guide, natural resources will progressively become less costly, hence less scarce, and will constitute a smaller proportion of our expenses in future years.”

          “The standard of living has risen along with the size of the world’s population since the beginning of recorded time. There is no convincing economic reason why these trends toward a better life should not continue indefinitely.”

          Maybe he wasn’t a real economist: he was a professor of business administration at the University of Maryland and a Senior Fellow at the Cato Institute at the time of his death. Maybe professors of business aren’t taught that the Earth is a sphere, hence finite in size. But Simon certainly wrote a lot, and quite influentially, about economics.

        • Darin says:

          I think it’s closer to taking a quote from Summer’s out of context more than saying he didn’t believe what he said. Even if taken as a literal, strict statement, not in terms of economics, without knowing what kind of time interval Summer’s had in mind I don’t think anyone can say whether or not it was a reasonable statement, especially when economic advisors only have a shelf life of a few years. The same probably goes for Simon. Not finite in an economic sense doesn’t equate to not finite in the math sense, where there are only two states in that context. If Simon said that something wasn’t finite, he didn’t mean it was infinite (countably or uncountably ;) ). His main gist, at least based on what I’m seeing, was that you can’t just look at current reserves and extrapolate from there in an economic sense.

          The mathematical definition of “finite” is quite different from a useful economic definition.

          For instance, the quantity of services we obtain from copper should not be considered “economically” finite because there is no way of counting them appropriately. We should also consider the possibilities of using copper more efficiently, of creating copper or its economic equivalent from other materials, of recycling copper or even obtaining copper from sources beyond planet Earth.

          Therefore, a working definition of the total services that we could obtain from copper now or in the future is impossible to construct.

          I certainly wouldn’t say that someone isn’t a “real” anything outside of the obvious, “I’m not really from Mars” kinda stuff, but at the same quote sniping has happened to Elrich too, and I definitely wouldn’t state that he made specific predictions that turned out wrong, especially when he explicitly contradicted that.

          If someone managed to get a hold of Summers, ask him whether or not those statements actually meant that there isn’t a limit to how many people can live on the planet given certain conditions, and he stated that’s exactly what they meant, then I’d buy that, but as it stands I don’t think those quotes were anything more than any other quote taken out of context. Taking them a certain way certainly provides a polarizing and attention grabbing idea, but I think it’s ultimately more divisive than productive, barring a situation where someone actually sat down with someone, fleshed out the statements in very concrete terms, and asked them if what they meant is equivalent to the concrete version like they did with Elrich.

        • Darin, methinks the Summers quote speaks for itself. I haven’t yet found the surrounding text. Alas folks like Summers don’t have a limited shelf like as economic advisors – to the contrary, the man even got in Obama’s team (so much for “change”…). Here’s another Summers quote from 1992:

          I think the economic logic behind dumping a load of toxic waste in the lowest wage country is impeccable and we should face up to that. The costs of pollution are likely to be non-linear as the initial increments of pollution probably have very low cost. I’ve always thought that under-populated countries in Africa are vastly UNDER-polluted, their air quality is probably vastly inefficiently low compared to Los Angeles or Mexico City.

        • p.f.henshaw says:

          The real answer to whether economists believe what they say depends on whether you are open minded enough to discover what subject they are referring to. I think they generally do believe and are most often correct about the actual subject of their sentences, though most everyone else would think they are referring to something else.

          What you need to do is ask what subject is it that would make their statements true. Typically what I find is that statements by experts, particularly, are referring to their theories and not the natural world apart from their theory. Experts very easily lose any separate awareness of the natural world. So for a theorist to say “the world is X” comes from and refers to their own abstract representation of the world.

          As to natural limits, theories have no inherent scale, just like a string of numbers has no limit and can refer to anything. So there never are any limits to projecting a theory.

          I did a recent blog post responding to John Fullerton’s discussion of SCALE as the key factor missing from economic thinking, fyi “Natural organization, giving things s.c.a.l.e”

        • Darin says:

          I don’t think any short comment can be taken at face value Martin, especially if it’s vague and was part of a live conversation or similar, given that everyone can make mistakes and it’s not like we’re writing out a proof using very strict language.

          Don’t get me wrong, I don’t know if Summers is a stand up guy or a complete jerk, but I don’t think anyone can reasonably say that quote sniped text is indicative of someone’s views, especially if it’s taken out of context. You may not believe that as Summers said, the quote about pollution was a “sardonic counterpoint, an effort to sharpen the analysis.”, but that doesn’t mean it was completely serious. Who knows…

          That said, if someone really thinks that a snippet of quote from some economist can stand on it’s own, why can’t the same be said for Elrich’s statements, even if he explicitly denies that they were predictions just like Summers denied those comments were serious? In both cases someone would restrict their citation to only a few lines and without any form of context they would both look, for lack of a better word, nuts. The problem there is that anyone could probably quote a restricted version of what someone else says, interpret that in a specific way, and use that as evidence that they’re “nuts”, which is extremely counter-productive considering that the vast majority of serious stuff from most people, and that includes Summers and Elrich, is both useful and valid.

          Since climate change is an economic, environmental, and pretty much all around problem, it seems to me that a lot of these extremely strict, borderline ad hominem statements are meant to “poison the well” so to speak, since significant action will require significant consensus, but maybe I’m just speculating too much. It’s not like any of those companies/countries involved in fossil fuel production would have any incentive to polarize people in an effort to delay action. ;)

        • Thomas Fischbacher says:

          Darin wrote:

          “climate change is an economic, environmental, and pretty much all around problem”

          Indeed. And it is quite relevant what economics has to say about it, for this explains a lot about how we got into this situation in the first place.

          Some months ago, I wrote an article about this for the PRI blog:

        • Darin says:

          Thomas, just like I mentioned to Martin, I don’t think a small portion of something is representative of the whole. I agree with your critique, however I don’t agree with your conclusion that it represents a massive systemic problem in economics. Just to provide some context, “Markets and hierarchies: analysis and antitrust implications: a study in the economics of internal organization” has been cited ~15k times, about an order of magnitude more than the Nordhaus book, and it’s just a small subsection of economics. ~1.2k citations may seem like a lot, but it’s a drop in the bucket.

          Nordhaus and other economists got it wrong, people do all sorts of unpredictable (by that model) things if food is scarce, geo-engineering will cost a lot, and so on, but that doesn’t mean all of economics is unsound unless you would also state that all of ecology is unsound because the world3 model used in LTG (cited by ~6k) allowed costless economic substitution. Unless of course you know of a way to turn dirt into gold at no cost, in which case shoot me an email! ;)

          I said it before, well, not in so many words, and I’ll paraphrase it again. I don’t think generalizations like these are useful. There are going to be cranks in any field, and these cranks may even be brilliant in some aspects, but I don’t think that means we can reasonably make statements about an entire field based on some papers and citations, just like I don’t think we can reasonably make statements about a person based on a few sentences with no context.

        • Darin says:

          I’m not implying Nordhaus is a crank either, he could have simply messed up, but my point is that people who are cranky or who mess up aren’t representative of an entire field, unless of course the whole field is cranky/messed up, but in that case someone would have to do a lot more than read a few papers to establish that.

        • Thomas Fischbacher says:

          Let me be very clear about this: Nordhaus’s book may be a problem, but the actual and important problem is the inability of the discipline to identify seriously flawed work as such, and eliminate the mistakes therein from further scientific discussion and investigation.

          Rather, there are lots of other publications that also build on this utter rubbish.

        • Thomas Fischbacher says:


          “but that doesn’t mean all of economics is unsound unless you would also state that all of ecology is unsound because the world3 model used in LTG (cited by ~6k) …”

          The “Limits to Growth” study does not belong to the field of ecology.

        • Florifulgurator says:

          Thomas, your article on Nordhaus is amazing and revealing. I have to put him on my list of stupid economists.

          Actually I didn’t want to continue with the economists bashing here…

          But now I need to cite Milton Friedman on oil… As we now know, regarding oil the invisible hand of the market didn’t exercise the wisdom it should have had according to Friedman. It just failed miserably, like General Motors.

          So: If the market wasn’t able to sort out the rather simple peak oil thing – then how would it be able to sort out the dynamics (with its vicious delays) of climate change, agriculture degradation and population momentum?

          Now (having opened an after-pub beer) for Milton Friedman:

          Excuse me, [oil is] not limited from an economic point of view. You have to separate the economic from the physical point of view. Many of the mistakes people make come from this. Like the stupid projections of the Club of Rome: they used a purely physical approach, without taking prices into account. There are many different sources of energy, some of which are too expensive to be exploited now. But if oil becomes scarce they will be exploited. But the market, which is fortunately capable of registering and using widely scattered knowledge and information from people all over the world, will take account of those changes.

          (secondary source)

        • Thomas Fischbacher says:


          there is much more to be said about Nordhaus. Less than two years before he published his well known climate change economics book, he published an article in which he tried to debunk the validity of the very mathematical modeling methods on which his climate change book also is based.

          But concerning “the invisible hand of the market”, a key problem is that this idea obviously does not work if everybody just leans back in complacency, relying on the invisible hand to sort things out. Evidently, we did NOT invent a way to produce cheap and clean energy in abundance, and now the invisible hand just tells us that, well, the price of oil indeed was wrong for a long time – that’s how I interpret a situation in which it is more profitable to just hoard oil than let industry have it…

        • Web Hub Tel says:

          Now (having opened an after-pub beer) for Milton Friedman:

          Milton Friedman is quite a source for what some consider a cornucopian vision.I have quoted him many times, and always put the contrary viewpoint along side what he says. His reputation was so great that his viewpoints live on amongst his disciples and fans.

        • Giampiero Campa says:

          Just about every introductory econ text starts out with the definition of economics being roughly how finite time and resources are spent.

          I think that this is a very interesting observation. Microeconomics deals with resources that, by virtue of not being available in infinite quantities, have a price, and therefore generate supply (and demand) curves.

          The dynamics of resource depletion (and to say the truth almost any other dynamics) is not really considered, at least at the introductory level. In fact, equilibrium is often studied at a fixed time, pretty much disregarding what happens next.

          However it is sometimes stated more explicitly that if resources become scarcer their price becomes higher, (assuming common shapes of the demand and supply curves), and the resource is sold and used in even smaller quantities, therefore implying that resources are never depleted completely.

          So basically the finiteness of resources plays a role only by allowing such resources to have a supply curve, and that’s pretty much it, as the market decides the allocation.

          Now, despite this mostly static picture, growth is embedded in economic thinking because the promise of individual future gains moves resources (and especially money) to increase production. For example money can be lent, but only at the promise of gaining a certain percentage in return. This promise can be maintained, in average, only if the total value of things that are sold increases by the same percentage.

          This is actually a semi-reasonable rough approximation of how things have worked so far, and as a consequence often long-run macroeconomics models are just linear models that represent small perturbations about equilibrium points in a space of growth rates. This means that the underlying (exponential) growth is sort of taken for granted, which i think leads economist to under-appreciate the fact that exponential growth cannot be sustained.

          Other than that, there is, i think, a widespread habit among economists of thinking that past trends can be extrapolated in the future, (perhaps because there are no better models to rely on when looking at the data), and an excessive trust in the ability of free markets to solve problems efficiently. I cannot back this up with real quotes right now, it’s just my personal feeling gained from reading economics books and blogs, and actually talking to economists.

        • Darin says:

          Thomas, as a social science, what do you think an entire field like economics should do in this case? For that matter, since you’ve gone through this in more detail than anyone else around here, and appear to have a good idea as to what should be altered, why not suggest those changes to the author/s, or better yet, make those changes yourself?

          The point I’m trying to make in general is that context matters a lot, and while criticism of an economist, ecologist, or anyone else who makes a poor model is warranted, that criticism of a quantitative effort, even if it’s lacking, doesn’t necessarily translate into some fundamental deficiency with social sciences that tend to focus more on qualifiers . Then again I’m just a lay person, so if you know that you’ll get more done about climate change and other problems criticizing other fields than offering constructive suggestions as to what should be changed, then go for it. Personally that sort of approach bugs the hell out of me, but maybe people in the social sciences and hard sciences are different.

          Giampiero, I’m not sure if characterizing economists as always believing in the invisible hand of the market is accurate. Even Summers, who doesn’t appear to be very popular around here, and has been used as an example of the problems with economics, stated explicitly that in certain ways “market failure is absolutely pervasive” (About nine minutes in here, So I think that most serious discussion depends on where someone draws the line between a functioning market and a failing market. It could be extremely narrow on both sides, aiming for near perfect competition and lack of externalities on one end, and on the other tolerating massive externalized costs and behavior that boarders on that of a cartel.

        • Giampiero Campa says:

          Giampiero, I’m not sure if characterizing economists as always believing in the invisible hand of the market is accurate.

          It is NOT accurate at all, I agree. I am sure the majority of economists know full well (at least at the theoretical level) when and how market fails. What i meant is that there still is a tendency to overestimate the power of the invisible hand, by many economists, at least if you include the “Chicago school”.

          To be fair this is probably getting better since the crisis has left many wondering about the relevance of the most orthodox schools of thought.

          The link is interesting, and he uses reasonable words. At the same time you can sense his slightly biased position towards public-private partnerships, many of which have been proven to be a success, at least in Europe.

        • Darin says:

          One of the big problems with the US, and I think Summers was alluding to this when he mentioned that public intervention may not be any better than anything the private sector can do, is that we haven’t always provided an environment that will help whatever we’re subsidizing. Europe subsidized public transportation and increased fuel taxation, which anecdotally resulted in something better than what we’ve seen with Amtrak w/o an increase in fuel taxation in the US.

        • Ivan Sutoris says:

          I’m a bit late to this conversation, but I’ll try to share my thoughts on economics anyway. I don’t see any problem in Summers’ statement – resources can be finite and at the same time, resource constraints may not be binding “in the foreseeable future”. Of course such statement may be right or wrong, yet it has nothing to do with assuming unlimited resources or violating laws of physics. Simon’s quote is less defensible, but on the other hand, somebody from Cato Institute is not exactly a representative of mainstream.

          Regarding the more general issue whether economists pay attention to limited resources, it is important to understand that economists are not trying to build one huge, unified model of whole economy. Instead, they use separate models and assumptions for studying different questions, and in many of those questions (e.g. evaluating short-term impacts of fiscal stimulus), natural resources are not directly relevant. That doesn’t mean that they are always ignored – there have been neoclassical models with finite resources, going all the way back to Hotelling’s 1931 article (brief survey here).

          Obiously this doesn’t mean that economists are free from criticism – assuming costless geoengineering technology like Nordhaus did is, indeed, silly (unless he clearly marked it as a hypothetical scenario). But it would be shame if insights of economists were ignored completely. After all, people do react to incentives and if prices of resources go up, they will be more likely to switch to more sustainable technologies. Trade-off between growth and enviromental regulations does exist and shouldn’t be ignored. And if future generations will be richer than us, questions about how the costs climate change mitigation should be split is completely legitimate.

        • Thomas Fischbacher says:

          Ivan wrote:

          “And if future generations will be richer than us, questions about how the costs climate change mitigation should be split is completely legitimate.”

          Note that the discussion in economics has a serious asymmetry here: on the one hand, the idea of sharing the burden with future generations is raised, but on the other hand, the question is avoided what the price of high quality fuels would be if future generations could bid for it as well.

          The rate at which oil prices have been rising over the last decade quite clearly indicates that the 20th century ideas about how to value this resource were badly flawed.

        • Thomas Fischbacher says:

          Darin wrote:

          “Thomas, as a social science, what do you think an entire field like economics should do in this case? For that matter, since you’ve gone through this in more detail than anyone else around here, and appear to have a good idea as to what should be altered, why not suggest those changes to the author/s, or better yet, make those changes yourself?”

          The problem with the discipline of economics is that the scientific quality control process is completely broken. Take, for example, the colorful diagram from the Executive Summary of the Stern Report. (John showed it somewhere, but I cannot find it at the moment.) Take Stern’s policy suggestions, find the “5% chance for the outcome to be worse than this, given present state of knowledge” point on the top of the diagram, draw a straight line down from there, read off the outcome.

          It is quite evident that, if similar safety planning methods were common among engineers who build transport systems, the entire discipline would be in jail.

          A key problem is that many economists like to use the ivory tower to shield themselves from external criticism. I see this even to the extent that young people who only recently have started their training in economics frequently use “template excuses” such as “as a non-economist, you are not qualified to criticize economics” (pardon? As a non-alchemist, I am not qualified to criticize alchemy?! Every scientific discipline has some overlap with other disciplines, and there definitely are ways to validate or invalidate many claims. Note that quite a few ideas in economics actually can be traced back to concepts concerning thermodynamic equilibrium in physical chemistry.)

        • Darin says:

          Thomas, I don’t think any single event is reflective of an entire field. Even if something is peer reviewed, there’s no guarantee the peers will catch problems immediately or possible ever if no on else raises any objections. The whole Bogdanov Affair didn’t imply that theoretical physics or even the journal their mishmash “papers” were published in wasn’t legitimate. The only reasonable conclusion is that just about anything can slip through given the right conditions and that different journals and fields have different standards, which is pretty much a given. It’s not like every mention of a bad paper will be struck from the official records of the world and those involved will have their degrees revoked. Generally speaking poor papers fall by the wayside, and while they may be cited in publishing circles for a while in the worst case situation, that still doesn’t make them a good example of a field as a whole. Now if someone did a meta-analysis of all the papers in a whole field, then sure, they could be critical of it based on the reams of good data they’ve generated, but one paper is just one paper.

          The same goes for a paper’s use. If it’s junk and it’s being cited by a policy maker, then the policy maker is really the problem. An economist has as much control over the economy as a biologist has over the natural world. Engineers are kinda rare in that they participate in a disciple that’s very practical and easy to quantify, as opposed to any social scientist. Even a biologist as head of the EPA or something would have an easier time since the natural sciences are well understood relative to the social sciences.

          I suppose any hiding behind the Ivory Tower happens in any field, but I’m not sure if social scientists do it any more than natural of physical scientists, and that’s gonna be really hard to quantify since there’s no discrete measure of whatever hiding behind an Ivory Tower is. Do you have a link to any of these templates? I haven’t heard about them.

          And while that comment wasn’t directed at me, I’m also not sure if any sane economist would say that oil prices were a good example of the markets working. Cartels by definition are market failures, as are externalities and subsidizes/tariffs, and any market that exhibits these, like oil, is going to be very broken/flawed.

        • Thomas Fischbacher says:


          problem is though, as I also mentioned (with reference) in my article, that this work actually received a prestigious prize – as “work of enduring quality”.

          That’s not that easy to overlook or discuss away. The evidence speaks a clear language: People like Nordhaus – and when it comes to climate change also Thomas Schelling – are a problem. Or rather, society’s inability to recognize these charlatans for what they are, is the actual problem.

    • Thomas Fischbacher says:

      Concerning techniques and calorie yields from, well, let’s not use the term “organic” but instead speak of non-fossil-fuel-enhanced production, let me give two rice related examples.

      One is from the FAO: a yield comparison of different growing methods:

      Note that the highest yields were obtained using an integrated low input rice/duck/azolla(/fish) farming system. Ducks do the weeding and manuring, and numerous other things. Azolla fixes nitrogen and feeds the ducks, etc. One of the main proponents of this method is Takao Furuno.

      Another one is SRI – System of Rice Intensification:

      Do take a look.

      However, as I say, questions about how to feed the population often have the problem that the discussion gets distorted by emotions in a problematic way. The basic question really is: what factors influence human population, how do we feel about that and why, and what can we do to avoid problems we would strongly prefer to not encounter? The idea to keep on expanding food production to keep a growing (not only due to births, but also due to people living longer) population grow further somehow misses an important point.

  13. Giampiero Campa says:

    If we look at present soil degradation rates alone, it is patently clear that we see major changes ahead. In the long term, we just cannot hope to keep on feeding the population using methods that keep on rapidly destroying fertility. So, we pretty much know that something will happen there.

    So what will it look like when “something will happen” ? Assuming that all the land that can be used to produce food is currently used (but the back of the envelope calculations from Flori suggest that this is NOT true yet, because there are not yet 14 billions of us, and because we are using higher-yield non-sustainable agriculture) this will mean a sharp raise in food prices.

    A sharp raise in food prices will likely mean famine and death for some of the poor people in poor nations, and maybe a slight change of diet in the richest nations. This might or might not mean wars, depending on how sharp will the change be. Slow changes might go relatively unnoticed, but they will still create a more dangerous world.

    I guess we are stuck in a local minimum in which it is still marginally cheaper for the food producers to spend more money in fertilizers than it would be to worry about other solutions. It’s unclear to me whether a much higher price of fertilizers and/or a much lower yield will move us out of such minimum.

    • p.f.henshaw says:

      We can be much more precise about what happens I think. Asking what it means that “something happens” is indeed the fascinating question. I say “fascinating” because it exposes our notorious inability to imagine what reactions will be caused in the future to alter present trends we see clearly can’t last. We don’t train our thinking to do that, but mostly just “wait and see”.

      Here the question is more easily answered, that what “something happens” means for degrading resource capacities while steadily increasing demand is “demand systemically exceeding supply”. That began to occur about 10 years ago, in the form of the food and fuel resource markets becoming increasingly slow in recovering from snags in delivering supplies to the economy.

      That’s implied by the price movements, that increasingly don’t return to “normal” after supply shocks. Everyone is blaming the weather and politics, crop failures, and speculators, etc. Those create the supply shocks hitting our resource supply system. They are not at all the reason why the supply system never recovers, and prices don’t come back to normal. The reason for that is the comparatively slower ability of the supply system to meet ever growing demand, a.k.a. “peak everything”.

      That seems to be the general environmental description of what you see in the world commodities price curve. We have repeatedly higher price spikes as needed to quench unmet demand, and floor prices that have been basically rising at ~20% per year since increasing supply started becoming ever more costly rather than ever cheaper, as natural resource constraint.

      Click to access ASustInvestMoment-PH.pdf

      The problem is that the economy works with physical systems, most of which are unrecorded and mostly take care of themselves, and so business and finance came to rely on converting everything to money, and only measuring change in %’s. So that largely strips the minds of decision makers of concepts about how energetic natural systems respond to being squeezed.

      “What happens” is those systems change their behavior, and that subject doesn’t come up in discussions about what the problem is.

      • Giampiero Campa says:

        The reason for that is the comparatively slower ability of the supply system to meet ever growing demand, a.k.a. “peak everything”.

        From the numbers given above and below it looks (to me at least) like the part played by soil erosion in this “demand outstripping supply” process is still comparatively small. So it might be argued that other shortages will “make something happen” (most likely that will mean reducing the population) way before soil erosion becomes the most important factor. If this is the case then maybe at some point the high price of fertilizers will make more convenient for food producers to switch to sustainable agriculture. Food prices will still stay high, just food producers will make slightly more money using sustainable agriculture.

        Now, if soil erosion itself becomes the primary cause of lower yields and hence permanently higher and increasing food prices, why would that alone be an incentive for producers to switch to sustainable agriculture ? People (the ones who are still alive anyway) will not stop buying food, so producers will be doing just fine.

        So the only way towards sustainable agriculture (aside governments deciding to step in with subsidies) is if something needed in the food production process becomes so scarce, and therefore expensive, that food producers decide that the sustainable way is cheaper.

        Anyway, i don’t know, this is just me thinking out loud, since i don’t have a good grasp of how these things work yet.

        • Thomas Fischbacher says:

          Ah, not all soils and climatic conditions are as in Japan. Note in particular that Japan’s climate is not arid. That’s another reason why such a Fermi calculation is quite nonsensical. Incidentally, my wife is from a region in Germany where the soil is so poor that it could not support any major town in pre-fossil times – so this is an area with mostly only villages. I still remember how fascinated she was when she first pulled a carrot from my mother’s garden — “wow, I didn’t know one can do this without a hoe…”

          There is more to erosion than just the loss of soil fertility; plowing up the topsoil causes some breakdown of its organic compounds; this is responsible for about 1/4 of our present anthropogenic CO2 emissions. If we approached food production in a different way, we could even change the sign of that contribution.

          A big problem is that most present-day cost-benefit analysis approaches to food production are way too simplistic and do not take many long term effects into account. This concerns in particular usage and management of water (including the problem of salination). Basically, if farmers can make a profit today from a method that seriously damages the soil over a decade, quite many will these days actually go for it. Historically, such mis-management has often led to violent conflict.

          Sometimes I wonder whether there is a relation between how evolved cultural wisdom and philosophy is and how long society has been in contact with the soil that supports it. I am not especially surprised to see thinking in a very old culture, like the Indian one, being dominated by the concept that everything has to go in cycles, while a culture that only very recently came into contact with new abundant resources, like the Northern American one, does not pay much attention to management practices that have long term viability.

          Concerning the role of farmers, I think I already can see what will happen to them. Note that farmers these days produce commodities for international markets — they are not self-sufficient, or only in very rare cases. As such, they also have expenditures. And, in particular, it is often them who carries most of the risk that is associated with erratic circumstances such as the weather. So, as farmers are dependent on a number of things, in particular credit, they can easily come under tremendous pressure. We have seen waves of farmer suicides in India, and given the present structure of the “agricultural industry”, I think this will become a much more widespread phenomenon unless something changes.

          Vandana Shiva (incidentally, she also has a PhD in quantum physics; her thesis was on locality and hidden variables) knows quite a few things about these issues. Here is one article by her:

        • Giampiero Campa says:

          Thomas, i am a little unclear on what is the point you are trying to make here.

          I am fine assuming that soil erosion could soon become the primary cause of higher food prices, higher spikes with all the related dire consequences, even for the farmers.

          So are you saying that this will eventually make sustainable methods more economically viable than the alternatives ? or are you saying that it will never happen (without governments stepping in) ? or are you saying something completely different ?

          To me it’s clear that eventually physical limits will force population growth to become zero or even negative for a while. I am just trying to think about which is the most likely way in which that will happen.

        • Thomas Fischbacher says:

          Hm, I think the problem why we have difficulties finding a common perspective here is that you try to flatten things back to the “what does it mean for commodity prices” question, while I maintain that this thinking is one of the causes that brought us into this situation, as prices are agnostic to so many things.

        • Giampiero Campa says:

          True, I am trying to answer the question(s) “what higher food prices and/or higher energy prices will mean for the adoption of sustainable agriculture”, and I am implicitly assuming that farmers will not spontaneously switch to sustainable agriculture if that implies an economic loss on their part.

          I am not trying to answer the question of “which way of thinking will maximize our survival likelihood”. That does not mean that i don’t appreciate the relevance of this second question, or that i am unwilling to explore the effect of other assumptions, it’s just not the question i was trying to answer right now.

  14. Thomas Fischbacher says:

    Hm. What will it look like when “something happens”? That all depends on whether we try to make an effort to understand the inner mechanics of key processes, or whether we, as a society, try to avoid thinking this through — for using one’s brain seems to be a painful process to many.

    First of all: theoretically, present-day agriculture probably could (in the short term) feed 11*10^9 people straightaway without any major change concerning just calories, if we collectively drastically reduced meat consumption and stopped growing biofuels for inessential applications.

    There is quite a useful book on food shortage situations by Fred Cuny, “Famine, Conflict and Response”. Cuny was a practitioner who went out into affected countries and worked on the ground, with the people, until he got killed in Chechnya in 1994(?). He is very clear about the importance to discern between situations where there is not enough food to feed the population – a “food shortage problem” – and situations where people do not have the means to purchase enough food – an “entitlement problem”. Most famines which we have seen in the recent past were of the latter type.

    Let me use a chemical equilibrium analog to explain this — for, actually, quite some of the ideas of modern economics can be traced back to the idea of chemical equilibrium, in particular to Gibbs.

    There are some ion species that can lower Gibbs enthalpy by doing a redox reaction among themselves. Cu+ is not stable in aquatic solution, it will disproportionate according to 2 Cu+ = Cu + Cu++, because it is thermodynamically more advantageous to let one copper nucleus have two 4s electrons and the other one none than to give each of them one 4s electron.

    Now, what happens if it is economically more profitable to invest 100 kilos of rice into producing biofuels to transport a business executive to an important appointment than to use that rice to feed a person that would otherwise starve to death — because the poor person’s economic output is quite limited in comparison to the business executive’s? If you just try to maximize profit, there is a clear, fairly inhuman, outcome in such a situation. (I must say that I sometimes seem to encounter difficulties when trying to understand how U.S. citizens think about such questions — I get the idea that their perception of such a question differs from the European one.)

    What’s going wrong here? Well, if you ask me, a key problem is that energy is priced at a totally bizarre level these days. There is one group of people in the U.S. who have learned — the hard way — that social cohesion is essential for their survival, who are well aware of the problem of abundant cheap energy destroying social structures, and keep on designing their own cultural rules to keep these damaging effects in check. That’s the Amish. Fascinating subject, the Amish and consciously designed rules for energy utilization. They do use electricity, for example, but one has to produce it oneself — Amish never would connect to the power grid.

    So, it is the multiple-orders-of-magnitude discrepancy between the price of energy/labour from fossil energy and the price of human labour that distorts the conventional economic analysis in many ways. This is where physicists can help a lot to set the picture right.

    So much about the deeper mechanics. But what will happen in the near term future? If we just allow things to continue on their present trajectory, we will see food riots (more of them) and political instability, in particular in countries where families spend a large fraction of their income on food. Egypt will be in a particularly difficult situation. The water situation will lead to major tensions in many places. In particular, there is potential for a major conflict Egypt/Ethiopia/Sudan/Saudi Arabia. For a long time, Saudi Arabia pumped water from deep aquifers to grow grain domestically, as they saw that if it came to another oil embargo, they would be very vulnerable to a grain counter-embargo. These aquifers now are pretty much depleted, and Saudi Arabia bought a lot of land for growing food in countries with an already difficult food — and water — situation. In particular, as we are talking about Nile water here on which also the Egyptians depend. Now combine this with the myopic view of some molecular biologists who think they can solve such multi-dimensional problems by engineering plants to use less water, the smell of profit opportunity from such crops, and the inability of a mostly gardening-illiterate population (also trained to religiously stick to the idea of problems being solved by future miracle technology) to resist being bamboozled by bombastically exaggerated claims. Now that’s quite a dangerous mixture…

    What can be done to make it less dangerous? First and foremost, people all around the globe by now are trained from an early age on to be mostly spectators, by the TV. It is important to demonstrate that, yes, one can indeed actually do something useful. As long as the masses just sit in their chairs and get up to actually do something only to participate in political riots and revolution, the situation will just deteriorate further. Note that revolutionaries typically actually do depend on the system they are trying to fight in numerous ways — hence usually morph into what they fought once they win. Second, people are at present mostly illiterate about (a) energy and (b) gardening. Many things were much easier if this were otherwise. So, there clearly is a need for education here. Proper education, not the “let’s sell some degrees” type.

  15. Thomas Fischbacher says:

    I must substantiate the above charge of charlatanery against William Nordhaus. This is a very serious charge, and one should not raise it lightly. There is more evidence against Nordhaus than what we discussed so far.

    He not only wrote about climate change, but also about finite resources. In an article he published not long before his climate change book, which is a response to the “Limits to Growth” update, he tries to make a very generic point about the fundamental non-predictiveness of the type of mathematical modeling used by the LtG team. The problem here is that if his argument had any substance, it could be applied without any change to his own DICE model for climate change!

    So, to him, “mathematical” objections only are relevant if they can be used to make a case against other people’s work – they don’t matter if they also question his own work.

    The article I am talking about is “Lethal Model 2” from 1992 – Google Scholar will give you a reference to the PDF. The reason why his argument is bogus is explained in introductory physics college textbooks, such as the German “Gehrtsen Lehrbuch der Physik” (it’s an exercise question in chapter 18).

    • John Baez says:

      Since you don’t post here very often, Thomas, you may not have noticed that I have a strict policy against insulting people. That includes people here, but also everyone else. Even if somebody actually is a jerk, a charlatan, or an idiot, you’re not allowed to say that here. You can, however, say what is wrong with their work. This policy is fundamental to making this blog a friendly, welcoming place.

      Since I invited you to give an interview here I’ll let you get away with using the word ‘charlatan’ in your previous two comments, posted while I was asleep. But no more!

  16. Thomas Fischbacher says:


    apologies – I did not notice. You are right that such terms evoke emotional reactions in some readers that are not helpful when trying to actually get to the core of the problem.

    Let me give some detail. This is Nordhaus’s article in question, “Lethal Model 2 – The Limits to Growth Revisited”:

    Click to access Lethal%20Model%202.pdf

    Right at the beginning of this article, Nordhaus claims that the Limits to Growth study cannot be taken as meaningful, for it belongs to a class of mathematical models that feature

    (a) discrete time steps, and
    (b) negative feedback.

    He proceeds to explain that we have learned in the 20th century that, generically speaking, such systems may exhibit chaos. The example he gives is just a slightly re-dressed form of the Logistic Map – period doubling bifurcations, Feigenbaum scenario, chaos, and all that. Hence, his conclusion, LtG is a rubbish model.

    The problem with this is two-fold. On the one hand, his argument is not valid, because the role of discrete time is to allow us to put a continuous-time model on the computer, and one can validate whether the discretization produces artefacts. As we all know, a one-dimensional continuous time system described by an ODE of the form dy(t)/dt = f(y(t),t) won’t exhibit chaos. The reason is simple: If you have two solutions y1(t) and y2(t), these evidently never can cross. This sets a very obvious limit to how bad 1-dimensional phase portraits can become. If you instead look at a clocked system with governing equation y_n+1 = f(y_n,n), there is nothing that prevents y from “jumping” and behaving in pretty wild ways.

    Evidently, some clocked systems approximate the behaviour of continuous time systems. Those are the ones we are interested in in this context here. In particular, we get such clocked systems by using some fixed-time-step discretization scheme when describing continuous physics. If such a discrete-time-version-of-continuum-physics 1-d model exhibits chaos, this is a clear indication that we are using too large a time step, for the continuous-time system won’t. Note that delta-y is delta-t*y’ (for y’ evaluated at an appropriate intermediate point), and if
    delta-y is “large”, this is an indication that we are using an inappropriate delta-t. Hence, no large jumps from one time step to the next in a properly discretized model.

    We see: it’s readily validated whether the approach to discretize time chosen is meaningful. Do results change substantially if we modify our time steps a bit?

    So, his criticism may be valid for some particular research article containing simulation work that does funny things if one slightly modifies the time step. As a blanket criticism of all research that solves ODEs by non-analytic means, it certainly has no substance.

    Furthermore, the other issue with this is that his DICE model for climate change itself uses discretized time steps. And evidently, negative feedback effects also exist in that model (more economic activity means more CO2 means more damage means less productive economy).

    So, his mathematical objections invalidate his own work.

    Do take a look at the paper referenced above. I think it speaks a clear language. This very strongly smells of an effort to bamboozle a less math-savvy audience into believing strange things by presenting some math hocus pocus that is above what average citizens can comprehend.

    I consider this serious scientific misconduct. Even more so because the object of his study actually has massive relevance to society, and bad decisions may have incredibly harmful effects. However, somehow, as a society, we seem not to have learned yet to respond to such behaviour. One can get away with this sort of academic misconduct – but if, say, the German minister of defense is found out to have cheated when writing his doctoral dissertation (content-wise a highly irrelevant piece of work), the inevitable outcome is for him to lose his position. Isn’t that odd?

    • John Baez says:

      I haven’t read Nordhaus’ comments regarding discretization and chaos, only your account of them — and by that account they do seem misleading.

      However, my aim for this blog is to focus on science, not the possibly naughty behavior of individual scientists.

      Nathan Urban used Nordhaus’ DICE model in his work on the possible collapse of the Atlantic Meridional Ocean Circulation, which we talked about in “week305”. Nathan’s model required some assumptions on the world economy and its CO2 emissions. Back then, streamfortyseven asked Nathan:

      What assumptions do you make about population growth, and population, over this time scale of nearly 300 years?

      I said:

      I hope Nathan answers your questions in more detail: these are some issues I really want to understand! But just so he doesn’t need to repeat himself, this is from the interview:

      JB: … don’t the extrapolations become more unreliable as you keep marching further into the future? You need to model not only climate physics but also the world economy. In this calculation, how many gigatons of carbon dioxide per year are you assuming will be emitted in 2300? I’m just curious. In 1998 it was about 27.6 gigatons. By 2008, it was about 30.4.

      NU: Yes, the uncertainty grows with time (and this is reflected in our projections). And in considering a fixed emissions scenario, we’ve ignored the economic uncertainty, which, so far out into the future, is even larger than the climate uncertainty. Here we’re concentrating on just the climate uncertainty, and are hoping to get an idea of bounds, so we used something close to a worst-case economic scenario. In this scenario carbon emissions peak around 2150 at about 23 gigatons carbon per year (84 gigatons CO2). By 2300 they’ve tapered off to about 4 GtC (15 GtCO2).

      Actual future emissions may be less than this, if we act to reduce them, or there are fewer economically extractable fossil resources than we assume, or the economy takes a prolonged downturn, etc. Actually, it’s not completely an economic worst case; it’s possible that the world economy could grow even faster than we assume. And it’s not the worst case scenario from a climate perspective, either. For example, we don’t model potential carbon emissions from permafrost or methane clathrates. It’s also possible that climate sensitivity could be higher than what we find in our analysis.

      JB: Why even bother projecting so far out into the future, if it’s so uncertain?

      NU: The main reason is because it takes a while for the AMOC to weaken, so if we’re interested in what it would take to make it collapse, we have to run the projections out a few centuries. But another motivation for writing this paper is policy related, having to do with the concept of “climate commitment” or “triggering”. Even if it takes a few centuries for the AMOC to collapse, it may take less time than that to reach a “point of no return”, where a future collapse has already been unavoidably “triggered”. Again, to investigate this question, we have to run the projections out far enough to get the AMOC to collapse.


      JB: What scenario, or scenarios, did you consider?

      NU: We considered a worst-case “business as usual” scenario in which we continue to burn fossil fuels at an accelerating rate until we start to run out of them, and eventually burn the maximum amount of fossil fuels we think there might be remaining (about 5000 gigatons worth of of carbon, compared to the roughly 500 gigatons we’ve emitted so far). This assumes we get desperate for cheap energy and extract all the hard-to-get fossil resources in oil shales and tar sands, all the remaining coal, etc. It doesn’t necessarily preclude the use of non-fossil energy; it just assumes that our appetite for energy grows so rapidly that there’s no incentive to slow down fossil fuel extraction. We used a simple economic model to estimate how fast we might do this, if the world economy continues to grow at a similar rate to the last few decades.

      Here’s the graph from his paper:

      Here’s what the paper says:

      For projections beyond the year 2009, future forcings from fossil CO2 emissions, from non-CO2 greenhouse gas, and anthropogenic aerosols are adopted from Nordhaus (2007) following a business-as-usual (BAU) emissions scenario, yielding cumulative fossil fuel emissions of about 4800 GtC from 2000–2300. The CO2 emissions are plotted in Figure 1. Land-use CO2 emissions decay linearly from 2009 levels to zero in 2100 and are zero thereafter.

      The reference to Nordhaus is:

      • Nordhaus, W. D. 2007. The challenge of global warming: Economic models and environmental policy, Technical report,, accessed May 2, 2007, model version:

      A writeup describing Nordhaus’ 2007 model is here:

      • William D. Nordhaus, A Question of Balance: Weighing the Options on Global Warming Policies, Yale University Press, New Haven, 2008.

      A version of this book is free online — just click!

      Since I’m just looking at this 248-page book for the first time right now, I can’t say much about where the curve above comes from. I will note, though, that on page 127 of his book, Nordhaus estimates that a total of 6±1.2 trillion metric tons of carbon are available to be burnt. Currently we’ve burnt about 0.54 trillion tons, and people are wringing their hands about the trillionth ton, with some estimating it will be burnt by around 2044.

      On the same page, Nordhaus estimates that the world population will level off at 8.6±1.9 billion.

      Anyway, I hope Nathan weighs in — this is just to get the ball rolling.

      Nathan said:

      I don’t intend to “weigh in” too heavily, since I’m not an energy economist. I can offer a few general points and pointers to references.

      Fossil fuel emissions in the “business as usual” (BAU) scenarios that are usually considered are not driven primarily by population growth. They’re mostly driven by an assumption of continued economic growth, particularly that the rest of the developing world will eventually grow to consume energy at intensities similar to European, or U.S., consumption patterns (barring additional economic incentives to strive for low energy intensities).

      This is coupled to an assumption that there is a large amount of fossil carbon available in coal, tar sands, and oil shales (thousands of gigatons), and that eventual high energy demand will make it economically worthwhile to extract most or all of that carbon.

      This doesn’t preclude growth in alternative energy, simply that energy demand will be high enough that we’ll eventually want to dig up all that fossil carbon anyway, in addition to whatever alternative energy we deploy.

      Nordhaus’s DICE model is one way to turn these assumptions into an emissions trajectory. I should also point people toward the “Representative Concentration Pathway” (RCP) scenarios (overview here), which is what the IPCC will be using in its next assessment report.

      You can view (preliminary versions of?) these scenarios with this browser. The emissions projections go out to 2100, and they have “extension scenarios” (ECPs) for CO2 concentrations (not emissions) out to 2300.

      Their BAU scenario is called RCP8.5, and it is based on (but not identical to?) work in this paper, which outlines growth scenarios. (They don’t explicitly discuss fossil carbon constraints because in this scenario they implicitly assume that there is enough carbon to avoid peaking before 2100, the last date they consider.)

      All the other RCP scenarios are “stabilization” or mitigation scenarios where society opts to stabilize at below-BAU CO2 concentrations, or reduce emissions even further.

      The RCPs and ECPs look like this:

      RCP8.5 appears to have a slightly larger and sooner peak than the DICE BAU scenario, but is fairly comparable. Looking at the ECP concentrations, they seem to be assuming a similar total fossil resource constraint (~5000 GtC). The other ECPs assume stabilization at some CO2 concentration around 2150, or even a decline.

      I don’t know that I personally believe that we will go after ever last scrap of carbon we think may be in the ground. As I said in the interview, we intentionally considered a “worst case” scenario.

      I do think there’s a serious risk that we’ll extract, say, half that amount, and reach quadrupled (from pre-industrial) CO2 levels some time in the century after this one. That would require extracting what are currently low grade and unprofitable reserves, but they will become more profitable as other sources are depleted.

      Eventually fossil prices will rise, and alternative energy prices drop, to the point that it’s more profitable to switch completely to non-fossil energy. Absent price controls on carbon, I am not convinced this will happen fast enough to avoid some pretty high CO2 levels.

      There are other scenarios that lead to lower fossil fuel consumption, such as a global economic collapse leading to permanently depressed economic growth, or otherwise lower continued growth than we’ve seen historically based on our fossil energy economy. (There are also scenarios of enhanced economic growth…) Even so, a lowered rate of growth doesn’t necessarily imply a lowered final CO2 concentration, just that we’d hit it at a later date.

      I can’t venture my own estimate as to what I think will come to pass. For my policy work I choose to use what appears in the mainstream climate economic literature, and if those estimates change, so will my projections.

      It seems clear that all long-term economic projections are quite dicey: that’s not Nordhaus’ fault. However, some such projections may be wiser than others. So, to me the most interesting question is whether Nordhaus’ DICE model could be significantly improved without enormous amounts of work.

    • Ivan Sutoris says:

      Right at the beginning of this article, Nordhaus claims that the Limits to Growth study cannot be taken as meaningful, for it belongs to a class of mathematical models that feature

      (a) discrete time steps, and
      (b) negative feedback.

      He proceeds to explain that we have learned in the 20th century that, generically speaking, such systems may exhibit chaos.


      So, his criticism may be valid for some particular research article containing simulation work that does funny things if one slightly modifies the time step. As a blanket criticism of all research that solves ODEs by non-analytic means, it certainly has no substance.

      But Nordhaus is not saying that all dynamical models are wrong, or that solving ODE’s by numerical approximation is wrong (where did you get that?). He is talking specifically about Limits to Growth study’s claim that “overshooting” is a robust property of their predictions. His point is that claiming “robust” properties of solutions in nonlinear systems with possibly complicated dynamics and uncertainty in parameters should be done with caution. Sounds like a good advice.

      And anyway, he spends about two pages out of forty on this, so it’s not like that’s his main point. Accusing somebody of scientific misconduct is quite serious, and I think you are greatly exaggerating here.

  17. I’ve been wondering for long why much of the climate model bashing comes from “economists” and their camp (one notable exception being Dyson’s infamous “climate models are rubbish”). It looks the driver is more than just Serious People wanting to save their world view of eternal growth.

    So, a major inspiration of this seems to be Nordhaus?

    Methinks John is quite right with his “no insults” policy here, a virtual extension of university… But then, in a global arena “political correctness” can be overdone and gets counterproductive and harmful. The paradigmatic example is U.S. politics and media. Folks there get away with the most outrageous of BS (= bad science) and nobody takes them to task. The European shakes her head. If politicians can’t call a spade a spade, at least scientists should protest BS by pointing out BS using the proper technical term, BS. It’s long past time.

    • Ivan Sutoris says:

      I’ve been wondering for long why much of the climate model bashing comes from “economists” and their camp (one notable exception being Dyson’s infamous “climate models are rubbish”). It looks the driver is more than just Serious People wanting to save their world view of eternal growth.

      So, a major inspiration of this seems to be Nordhaus?

      Nordhaus accepts mainstream view of climate change. If you don’t believe, look at his latest study.

    • John Baez says:

      There are a lot of blogs and websites where scientists and other people spend their time debunking baloney, especially in such subjects as evolutionary biology and climate change. If there are any readers out there seeking such a blog for climate change, I recommend these:

      Skeptical Science.

      Real Climate.

      The Science of Doom.

      And on a more political charged note:

      Climate Progress.

      If you want to call someone a charlatan or say something is a bunch of BS, I recommend this last one!

    • Tim van Beek says:

      When and if I reach a sufficient level of understanding I will explain the main points pro and contra climate models, but it is a very complex subject. Nordhaus mentions a very important point:

      In order to have confidence in numerical results, we need to know how the results vary if we vary the boundary and initial conditions!

      (Maybe the authors of the “Limits of Growth” should have done that and did not, I don’t know.)

      In an ideal world we would be able to prove the stability of certain qualitative features that we use to infer our conclusions, which can be done for a lot of mathematical toy models, for example. For global circulation models this is not possible, they are just too complicated.

      A pragmatic viewpoint is to simply test the model by running it again and again with small variations in the boundary and initial conditions.

      Climate modellers do that, too, and they need your help: Please go to, donwload the necessary software to your computer and let it run a climate model when it is idle.

      At this point in the story of climate models, this is the only way to find out how stable these models are.

  18. Tom says:

    There’s been an article yesterday in the New York Times about permaculture, in case you’ve missed it Contains nothing already discussed above, I think, but perhaps the topic may get trendy, which would be nice.

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