Natural History Etc. – Hari Balasubramanian

The Fossils that Became Fuels

Did you know that fossil fuels – coal, oil, natural gas: the much-reviled hydrocarbons of today – are remains of long-dead organisms, essentially graveyards from hundreds of million years ago that were absorbed into the Earth’s bedrock? That coal is extracted from what’s left of ancient tropical forests and oil and natural gas from the remains of ancient marine microorganisms?

In these climate-challenged times, these should be well-known facts. But I wasn’t aware of them for many years. I’d thought of fossil fuels the same way I thought of minerals: as resources to be extracted from the earth, more abundant in some parts of the world than others. The qualifier fossil, which so unequivocally points to ancient life and distinguishes the fuels from the minerals, had completely escaped my attention. What kinds of fossils had left hydrocarbon molecules in such large quantities that are now fueling our lives and warming the world? How and when were they formed? I’d never bothered to consider these questions. Just goes on to show how shallow our understanding of everyday concepts can be! (Ask me about the phases of the moon or how a refrigerator works and I might struggle in the same way.)

The upside is that ignorance can turn into a source of wonder. I see now that every time we power our cars with gasoline, or consume electricity that comes from a coal or natural gas plant, or use the myriad products of petroleum (from asphalt to plastic bags to synthetic fibers), we are linked (however indirectly) to lifeforms from hundreds of millions of years ago. Fossil fuels should never have been burned in such large quantities, but they are a fascinating illustration of how the Earth’s deep history – stuff that we think belongs only to natural history museums and geology textbooks – is tangibly a part of our daily lives.

The Plants That Became Coal

Modern coal deposits date back to the tropical forests of the Carboniferous (literally coal-bearing) geologic period, which began about 323 million years ago. According to Wikipedia, coal is “formed when dead plant matter decays into peat which is converted into coal by the heat and pressure of deep burial over millions of years.”

Rocks from that period reveal the haunting imprints of plants that grew in these tropical forests. Take this fossil exhibit from one of my favorite spots in Amherst — the Beneski Museum of Natural History. It shows the 310-million-year-old trace of an ancient fern in a slice of Ohio rock. While the ferns I see every day in Massachusetts are short and carpet forest floors, back in the Carboniferous, they were tree ferns that grew nearly 65 feet tall (there are still tree ferns today in the tropics: the first image below shows the silhouette of one I recently saw in Costa Rica).

The environmental journalist Janet Marinelli describes other classes of plants that dominated the Carboniferous in this article . In addition to ferns, she highlights lycopods, ancestors of today’s club mosses. I have learned to recognize club mosses (second image below) on my daily walks. They are only a few inches tall — I incorrectly thought of them as ‘baby conifers’ or ‘hemlock nurseries’ — but a few hundred million years ago, they grew to an astonishing 130 feet. Marinelli also mentions calamites, ancestors of modern horsetails that I often spot along trails (third image below). They are short, but in the swamp forests of the Carboniferous, they rose to 50 feet.

Ancient ferns, club mosses, horsetails, and the earliest ancestors of the conifers: these, then, were the kinds of plants that got buried under dirt and rock for hundreds of millions of years. Heat and pressure slowly converted them to coal.

Here are some artistic renditions of what a tropical coal forest might have looked like. The visual feel of such a forest and the species of animals that inhabited it would have been quite different. Flowering plants and trees that dominate landscapes around the world today had not evolved at the time – they evolved much more “recently”, in the last 100 million years. This is why you won’t find oak, banyan, acacia, or any wildflower fossils in remnants of coal forests. The earth was also much warmer and more humid during the Carboniferous and the continents were differently aligned – North America, South America, and Africa were lashed together into a single supercontinent called Pangea. Places such as Pennsylvania and Virginia, where modern coal deposits are found, were at that time closer to the equator.

(If all this talk of geologic periods and tectonic activity is too much, I totally understand! There was a time when my eyes would glaze over too — the esoteric names and jargon-filled descriptions seemed so inaccessible. It wasn’t until I began to connect them with what we now take for granted that the Earth’s deep history started to resonate powerfully. Take something as vital as oxygen — the planet didn’t have much oxygen at all until the photosynthetic activity of cyanobacteria, starting two billion years ago, made it abundant on Earth, in the process creating the ozone layer that now protects us from harmful radiation. Or consider how plants and fungi established a symbiotic partnership on land 400 million years ago, turning barren continental rocks into the fauna-filled forests, savannas, and agricultural landscapes of today. Or consider how a large asteroid crashed into the Earth 66 million years ago, ending the reign of the dinosaurs, but not all of them – for we still have some of their descendants, the 9000-odd species of birds on Earth today.)

The Microorganisms that Became Oil and Natural Gas

The story of oil and natural gas is more complicated – at least for someone like me with only a faint idea of geology and microbiology. The current theory is that oil comes from the remains of tiny organisms that once thrived in warm, shallow seas in the Cretaceous and Jurassic geologic periods. This is roughly 200 to 66 million years ago, during the age of the dinosaurs. The sources of oil and natural gas are therefore younger than the coal forests of the Carboniferous.

I recently learned that plankton is the name given to a diverse class of marine micro-organisms that turned into oil and natural gas. A common feature of plankton is that they drift in the water and are unable to propel themselves against currents of water or wind. They include both microscopic plants (phytoplankton), which serve the same indispensable purpose as land plants, fixing the sun’s energy and thereby enabling other lifeforms; and microscopic animals (zooplankton) which feed on phytoplankton. The zooplankton in turn are a major source of food for larger organisms – whales, for example, feed on a type of zooplankton called krill.

Unlike land plants, which I can see and appreciate easily, these microscopic lifeforms are harder to relate to. (I can’t remember the last time I peered into a microscope – was it back in college or high school?) A 2010 New York Times article by William Broad discusses a type of single-celled phytoplankton called diatoms and claims they are “the source of the vast majority of the world’s oil”. There’s a lovely image in that article (below) that shows the varied geometry of diatoms – elongated, triangular, circular, star-shaped – and their iridescent colors.

If the marine micro-organisms theory is correct, then it implies that any oil-rich terrestrial region – North Dakota, Texas, the Middle East – must have been underwater once. (Such is the nature of continental movements that even North Dakota which seems so far inland and landlocked now was once covered by a shallow sea!) Just as important, the seas that covered the region must have had plenty of sunlight and nutrients that enabled an abundance of marine micro-organisms. When the shallow seas withdrew to expose land, the sediments – accumulated remains of dead micro-organisms collected over millions of years – became a source of oil and natural gas. The graphic above (from here) conveys it quite well.

The Middle East, which used to be under the Tethys Ocean, is an excellent example. The Tethys no longer exists but it was a predecessor to today’s Mediterranean Sea, the Indian Ocean, and the Black and Caspian Seas. When the continents slowly changed their alignments, the Tethys receded, exposing the sediment-rich Middle East. Thus, a fortuitous combination of tectonic activity and ancient marine life made the Middle East rich in oil and geopolitically important in the 20^th century. Another example, I suppose, of the Earth’s deep history manifesting in the modern world!

In closing, I should mention two books I leafed my way through while researching this article. They provide further context on the topics I’ve discussed here. The first is Echoes of Life: What Fossil Molecules Reveal about Earth History and the second is Vanished Ocean: How Tethys Reshaped the World. I also highly recommend the Deep Time exhibit at the Smithsonian National Museum of Natural History — it provides an engaging and awe-inspiring overview of Earth’s four-billion-year-old history.

Skunk Cabbages And Ferns

Living almost halfway between the equator and the north pole — the 45 degree North line is a few hours drive away from Amherst, in Vermont — has its downsides in the winter. But spring always brings great relief and beauty. And so many changes mark the coming of spring! You can track the arrival of migrating birds, watch turtles sun themselves on exposed logs, or — with the air so thick with pollen — simply enjoy a fit of morning sneezes.

A few days ago, while walking through the Lawrence Swamp conservation area in Amherst, I came across these skunk cabbages (Symplocarpus foetidus). In February and even in March, there was no sign of them. Yet by mid April scores of these low-lying plants carpet the moist, swampy parts of the Massachusetts. Skunk cabbages are named for their pungent odors but I don’t smell anything in their presence. I am always struck, though, by how vividly green they are (at least at this time of the year) and the very particular way in the leaves open up and curl.

Farther up, I found a section of the forest floor completely covered with skunk cabbages. Coiled spirals of ferns — called fiddleheads around here — will slowly begin to unfurl among them, adding to the visual drama. In fact, if you zoom in and look closely, a few tentative fern stalks are there already. For a few weeks in this patch of the forest, the two species will seem conjoined. But by mid summer, the ferns — equally striking in their appearance — will be tall enough to hide the skunk cabbages underneath. So the seasonal rhythms go!

Update, June 21st: This is how the same patch now looks, with the ferns very dominant.

The Wonder of Observing Another Species

When I was down with COVID in mid-September this year, two friends lent me Elisabeth Tova-Bailey’s The Sound of a Wild Snail Eating — a short, beautifully written account of a year in the author’s life. It was just the kind of reading I needed as I recovered. I finished the book a few weeks later at my usual slow — snail-like? — pace, completing a few paragraphs or a few pages each evening.

A viral infection — not COVID, for this was some decades ago — is also the central event in Tova-Bailey’s book. She catches it after a trip to Europe and finds herself in the middle of a debilitating illness that lasts two decades. The virus, she says, “re-wrote the instructions followed within every cell in my body, and in doing so, it rewrote my life, making off with nearly all my plans for the future.” The year that this book documents, Tova-Bailey is largely bed-ridden. Even standing or sitting up for a few minutes is hard.

On a whim, a visiting friend brings a wild snail (Neohelix albolabris) from the woods into her room. The snail makes its home in a pot of violets and in its early days — finding itself suddenly removed from its natural habitat and with nothing else to eat — consumed whatever paper it could find, paper being the only ‘woody’ thing in the room. This is the first of many remarkable details in the book:

The night before, I had propped an envelope containing a letter against the base of the lamp. Now I noticed a mysterious square hole just below the return address. How could a hole — a square hole — appear in an envelope overnight? Then I thought of the snail and its evening activity.

When Tova-Bailey puts some withered blossoms, the “snail investigated the offering with great interest and began to eat one of the blossoms”. Realizing that the snail needs a home that is closer to its woodland habitat, Tova-Bailey arranges for terrarium, a small habitat put together in a large glass bowl consisting of soil, mosses of various kinds, ferns and rotting bark. She feeds the snail with portobello mushrooms. (Check this Vimeo link to see the terrarium and hear a recording of the snail eating.)

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Excerpts From The Diversity of Life

I’d tried getting into The Diversity of Life twice before — 2018 or 2019 I think — but could not persevere beyond a few dozen pages. I wasn’t ready then for the kind of dense biology content that E.O.Wilson (the famous Harvard naturalist, known for his research on ants) was trying to communicate to lay audiences. In August last year — the beginning of my two semester teaching break — I picked up the book again. This time I sailed comfortably through. I read it over many months, savoring the details. Interesting how content that is so bumpy at one time can feel so seamless at another. (There was also an odd coincidence: I was about three quarters through the book when I heard of Wilson’s passing at age 92.)

The Diversity of Life exudes a kind of mystery that I found enticing. It was as if I’d stepped into a strange new world, not unlike Alice’s Wonderland or Tolkien’s Middle Earth. Except that Wilson’s world — populated with the innumerable lifeforms of our planet and the ecosystems they inhabit — is very real of course. (Innumerable quite literally: for no one knows how many species there are on earth.) In the excerpt below, one of my favorites in the book, Wilson illustrates that to fathom the diversity of life one cannot think of space in “ordinary Euclidean dimensions”. Rather one has to think in “fractal dimensions”, with microscopically smaller ecosystems nestled within larger ones:

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Reflections on Phenology, Species Relationships and Ecology

This essay was first published at 3 Quarks Daily.

The slim, green book Natural History of Western Massachusetts is one of my favorites. Compressed into its hundred odd pages are articles and visuals that describe the essential natural features of the Amherst region, where I’ve lived since 2008. I turn to it every time something outdoors piques my interest — a new tree, bird or mammal, a geological feature.

One section that I particularly enjoy is the ‘Nature Calendar’. The calendar gives predictions on what to expect in each phase of a month; there’s approximately one prediction for every 3-day period. In early November, for example, it says “dandelions may still be blooming in protected areas”, and indeed some wildflowers do retain their bright colors despite freezing fall temperatures. It also says for the same month that “flocks of cedar-waxwings may be migrating through the region”. This was such a specific claim, but it is accurate: I was startled to see a flock of nearly a hundred waxwings swirling around bare trees on a rocky mountaintop this November.

The scientific analysis of such seasonal patterns is called phenology. Wikipedia defines it as “the study of periodic events in biological life cycles and how these are influenced by seasonal and interannual variations, as well as habitat factors (such as elevation)”. It’s a clunky, textbook kind of definition but the gist is clear enough.

I find myself drawn to phenology for many reasons. After thirteen years in Massachusetts, the seasons are familiar, yet each season there are always new details that capture my attention. One year I might realize how pine needles carpet the forest floor in the summer, creating a distinct soft texture on hiking trails; in another I might notice that only the chipmunks disappear in the winter while the squirrels stay active. The number of such details that I am yet to observe seems endless. They remind me that familiarity — and the boredom that appears to lurk beneath — are only mental constructs, that there is always something interesting to discover.

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Wonders of the Scientific Backstory

Earlier this year, on my usual walk through the UMass campus, I passed by a rock that was on display next to the Science Center. I had probably passed it dozens of times before but never noticed it. (Why do things that we miss all the time suddenly catch our attention one fine day?) The rock – dark grey, about four feet wide, two feet tall, sliced to reveal contours in the cross section – was like others in northeastern US: so common and ordinary, it blended into the landscape. But that day I stopped to look at the plaque that was attached to the rock. This is what it said:

“Hawley Formation Pillow Basalt. This basalt was erupted from an arc volcano during subduction and closure of the Iapetus Ocean, approximately 475 million years old. Quarried from Hawley, Massachusetts.”

475 million years! I was intrigued: Was this the oldest inanimate solid body that I had ever seen? Had it always more or less retained its shape over millions of years? And what about the exposed rocky cliffs along interstates and the glacier-strewn boulders along hiking trails which I saw so regularly – how old were they?

I had paid little attention to rocks and boulders, but now they have moved to the foreground of my awareness. They have turned into sources of wonder, quiet messengers from an ancient time. And geology itself, which for a long time seemed like a forbidding science – with esoteric terms such as subductions, mantles and moraines – now seems indispensable to understanding the earth’s deep history.

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A monarch caterpillar

Although I’ve seen a lot of monarch butterflies in my years in Massachusetts, and even traveled to the forests of Michoacan in Central Mexico to watch millions of them congregate the winter, I’d never — surprisingly — come across a monarch caterpillar. But last month, at a roadside stop in the Adirondack Mountains of upstate New York, I finally saw one squirming on the leaf of a milk weed plant.

If everything goes well this caterpillar will metamorphose into a butterfly and will — all by itself — make the epic 2000-mile journey to Mexico.

The caterpillar sighting led me to check how monarchs have been doing in recent years. A good estimate of their numbers comes not from raw counts — it is very hard to count swarms of butterflies — but from the number of acres occupied by the migrant generation in Mexico at the peak of the winter. That’s the time of the year the butterflies are densely packed together on oyamel (fir) trees. So it’s a matter of identifying clusters of such trees, determining the perimeter of each cluster, and finally calculating the total area enclosed across all clusters. Mexican researchers, led by Eduardo Rendon Salinas, do this on an annual basis.

According to some recent references, the number of acres occupied by overwintering monarchs starting 2014-2015 (the year I visited) reads as follows:

2.79, 9.91, 7.19, 6.13, 14.95, 6.99, 4.9

A lot of ups and downs there with a seeming decline in the last couple of years. In contrast, the average acres monarchs occupied in the 1990s and 2000s was well over 15, and individual years frequently exceeded 20.