Serpentine Barrens


This is the Soldiers Delight Natural Environmental Area, a nature reserve in Maryland. The early colonial records of Maryland describe the area as a hunting ground for Native Americans. In 1693, rangers in the King’s service from a nearby garrison patrolled this area and named it Soldiers Delight, for some unknown reason.

It may not look like much, but that’s exactly the point! In this otherwise lush land, why does it look like nothing but grass and a few scattered trees are growing here?

It’s because this area is a serpentine barrens. Serpentine is a kind of rock: actually a class of closely related minerals which get their name from their smooth or scaly green appearance.

Soils formed from serpentine are toxic to many plants because they have lots of nickel, chromium, and cobalt! Plants are also discouraged by how these soils have little potassium and phosphorus, not much calcium, and too much magnesium. Serpentine, you see, is made of magnesium, silicon, iron, hydrogen and oxygen.

As a result, the plants that actually do well in serpentine barrens are very specialized: some small beautiful flowers, for example. Indeed, there are nature reserves devoted to protecting these! One of the most dramatic is the Tablelands of Gros Morne National Park in Newfoundland:

Scott Weidensaul writes this about the Tablelands:

These are hardly garden spots, and virtually no animals live here except for birds and the odd caribou passing through. Yet some plants manage to eke out a living. Balsam ragwort, a relative of the cat’s-paw ragwort of the shale barrens, has managed to cope with the toxins and can tolerate up to 12 percent of its dry weight in magnesium—a concentration that would level most flowers. Even the common pitcher-plant, a species normally associated with bogs, has a niche in this near-desert, growing along the edges of spring seeps where subsurface water brings up a little calcium. By supplementing soil nourishment with a diet of insects trapped in its upright tubes, the pitcher-plant is able to augment the Tablelands’ miserly offerings. Several other carnivorous plants, including sundews and butterwort, work the same trick on their environment.

In North America, serpentine barrens can be found in the Appalachian Mountains—Gros Morne is at the northern end of these, and further south are the Soldiers Delight Natural Environmental Area in Maryland, and the State Line Serpentine Barrens on the border of Maryland and Pennsylvania.

There are also serpentine barrens in the coastal ranges of California, Oregon, and Washington. Here are some well-adapted flowers in the Klamath-Siskiyou Mountains on the border of California and Oregon:

I first thought about serpentine when the Azimuth Project was exploring ways of sucking carbon dioxide from the air. If you grind up serpentine and get it wet, it will absorb carbon dioxide! A kilogram of serpentine can dispose about two-thirds of a kilogram of carbon dioxide. So, people have suggested this as a way to fight global warming.

Unfortunately we’re putting out over 37 gigatonnes of carbon dioxide per year. To absorb all of this we’d need to grind up about 55 gigatonnes of serpentine every year, spread it around, and get it wet. There’s plenty of serpentine available, but this is over ten times the amount of worldwide cement production, so it would take a lot of work. Then there’s the question of where to put all the ground-up rock.

And now I’ve learned that serpentine poses serious challenges to the growth of plant life! It doesn’t much matter, given that nobody seems eager to fight global warming by grinding up huge amounts of this rock. But it’s interesting.


The top picture of the Soldiers Delight Natural Environmental Area was taken by someone named Veggies. The picture of serpentine was apparently taken by Kluka. The Tablelands were photographed by Tango7174. All these are on Wikicommons. The quote comes from this wonderful book:

• Scott Weidensaul, Mountains of the Heart: A Natural History of the Appalachians, Fulcrum Publishing, 2016.

The picture of flowers in the Klamath-Siskiyous was taken by Susan Erwin and appears along with many other interesting things here:

Klamath-Siskiyou serpentines, U. S. Forest Service.

A quote:

It is crystal clear when you have entered the serpentine realm. There is no mistaking it, as the vegetation shift is sharp and dramatic. Full-canopied forests become sparse woodlands or barrens sometimes in a matter of a few feet. Dwarfed trees, low-lying shrubs, grassy patches, and rock characterize the dry, serpentine uplands. Carnivorous wetlands, meadows, and Port-Orford-cedar dominated riparian areas express the water that finds its way to the surface through fractured and faulted bedrock.

For more on serpentine, serpentinization, and serpentine barrens, try this blog article:

Serpentine, Hiker’s Notebook.

It’s enjoyable despite its misuse of the word ‘Weltanschauung’.

10 Responses to Serpentine Barrens

  1. Toby Bartels says:

    Typo (missing word):

    minerals made of which get their name

    Made of what? I'm dying of suspense!

    • Jason Erbele says:

      I think it’s a case of extra words (made of) rather than a missing word. The chemical make-up is indicated at the end of the paragraph following that line.

    • John Baez says:

      Toby wrote:

      Made of what? I’m dying of suspense!

      Hang in there, Toby! In the next paragraph I gave it away:

      Serpentine, you see, is made of magnesium, silicon, iron, hydrogen and oxygen.

      If I had to give a single formula for all the serpentine subgroup minerals, I guess it would be ‘hydrous magnesium iron phyllosilicate’: ((Mg, Fe)3Si2O5(OH)4). But it’s a bunch of different things. Chrysotile, for example, is used to make asbestos.

  2. Jason Erbele says:

    Fascinating quote about the Tablelands – Scott Weidensaul also mentions shale barrens. Is shale toxic to plants in a similar way that serpentine is? (Also, when did birds become mammals?)

    • John Baez says:

      Scott Weidensaul is a very good writer and he has a way of making everything fascinating. The slip—“mammals” for “animals”—was my fault, not his.

      I don’t think shale barrens arise from toxicity. Weidensaul says that black shale on the southern sides of mountains in the Appalachians gets blistering hot in the summer sun, and I guess water runs right off. The Nature Conservancy says this about their Potts Creek preserve:

      A shale barren is a steep, south-facing, eroding slope of thinly bedded, weathered shale, having sparse tree cover and little soil, found in the Ridge and Valley province from southern Pennsylvania to southern Virginia.

      At least three rare species native to shale barrens occur at Potts Creek: chestnut lipfern, Kate’s mountain clover and Virginia nailwort. Numerous other species not restricted to, but regarded as characteristic of shale barrens, are found here. These include Allegheny rockcress, Allegheny stonecrop, mosspink, and white-haired leatherflower.

      Trees that manage to grow on the barrens, such as red cedar, chestnut oak and Virginia pine, are small for their age, reaching about 20 feet in height and 15 inches in diameter. Like many desert trees, the trees at Potts Creek are dwarfed, twisted and gnarled by the elements. Thick, hairy leaves protect some shale barren plants against desiccation, and their deep root systems tap what little water exists.

      The uniqueness of the shale barren’s flora remained unnoticed until the late 1800s, when botanists collected plants on the shale slopes of Kate’s Mountain, West Virginia. To their surprise, many of these plants were new to science, and Kate’s Mountain become the type locality for a number of shale barren endemic species, including Kate’s mountain clover and white-haired leatherflower.

      So yet again, the harshness of the environment ironically leads to biodiversity—including the only cacti on the east coast of the US.

  3. Very specialized flora can be found in almost any inhospitable environment, I guess. In western India, laterite plateaus with heavy rainfall (and therefore very thin soil) have an incredible variety of highly specialized herbs, including several insectivores. A few plants are restricted to just one plateau.

    • John Baez says:

      Neat! I don’t know anything about laterite. Does it have some special features that make these plateaus inhospitable? (Like, maybe it’s very hard, so it doesn’t decompose much, so it doesn’t provide soil? Or maybe it doesn’t provide the minerals plants like?)

      • High metal content: iron, aluminum, nickel. Very porous, can hold a lot of water after rains. One of the most common subsoil rocks in the world: possibly the major component of the rocky layer below about a third of the land surface of the world. In these high plateaus, the rain washes off the soil, leaving the laterite layer exposed.

      • John Baez says:

        Cool, thanks for the information!

  4. John Baez says:

    My wife Lisa asked if the same unusual species were found in different serpentine barrens. The answer is yes, at least for the ‘serpentine aster’, Symphyotrichum depauperatum.

    It lives in 20 of the 26 remaining large pine barrens on the east coast of the US!

    • Danny J. Gustafson and Roger Earl Latham, Is the serpentine aster, Symphyotrichum depauperatum (Fern.) Nesom, a valid species and actually endemic to eastern serpentine barrens?, Biodiversity & Conservation 14 (2005), 1445–1452.

    Abstract. Serpentine aster, Symphyotrichum depauperatum (Fern.) Nesom, is the ‘flagship’ species of the eastern serpentine barrens, inhabiting 20 of the 26 remaining occurrences of significant size of this globally rare community type and long recognized as its only known endemic species. Previous studies have called into question both the validity of the taxon and its status as a true endemic of the serpentine barrens. We used amplified fragment length polymorphism (AFLP) analysis to compare seven serpentine barrens populations, one alleged diabase glade population, and two populations each of the two species with which S. depauperatum is lumped by some authors. Our analysis supports the validity of S. depauperatum as a distinct species, which grows almost entirely on shallow soils overlying serpentinite bedrock in Pennsylvania and Maryland, but it confirms an earlier hypothesis that S. depauperatum also includes small, disjunct populations on diabase glades in North Carolina.

    Now I need to learn about diabase glades!

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