Famously glacial in its origins, Martha’s Vineyard is a relatively recent creation, in essence a huge pile of rock, transported, tumbled, ground, crushed, puréed, and otherwise abused by a vast, fluctuating sheet of ice that reached its southernmost extent in what are now the northern fringes of the Island.
At the very largest scale, the rising and fading of the edge of that ice left behind what humans consider entire landscapes: ranges of morainal hills corrugating the up-Island towns, the broad central and southern plain of outwash evident at Katama, Quansoo, Dukes County Airport. The amount of debris deposited simply defies my comprehension.
At the very smallest scale, that whole epochal process comes down to individual pieces of rock, ranging from microscopic to the size of Waskosim’s Rock, each piece with its own history of physical and chemical interactions.
Clearly we’ve made progress since our mineral days: Martha’s Vineyard today, just a few millennia removed from being a sterile heap of sand and gravel, supports a famously diverse and productive ecosystem. With our pitifully short human perspective on these things, we take this wealth of life for granted. When you think about it, though, such greening of a sand pile is an utterly astonishing outcome. How did we get from that to this?
The answer is that soil formed: Ground or crushed minerals, with very little to offer a plant or animal, evolved into an organic-mineral hybrid that can support an entire ecosystem. From single-celled plants to oak woods, a succession of progressively more complex species and ecosystems have left parts of themselves behind, mixing with what the glacier left, adding nutrients and the ability to retain water. Just inches or feet thick, a living blanket of soil supports virtually every plant and animal that lives on land.
Vineyard soils started with colorful mishmash of sands and clays. Layers of different kinds of glacial debris piled on top of each other. Sometimes the layers were tumbled by subsequent advances of the glacier. In other places deep, flat layers of very similar sand accumulated.
It’s worth a field trip to visit places where the complicated anatomy of the Vineyard is on display. Look through the fence at the deep blanket of sand that forms the side of the Goodale sand pit. Hike to the cobble beach at Menemsha Hills, where recent landslides on the coastal bluff have brought a beautiful mix of clays and sands down to beach level. Or inspect the root ball of one of the many recently storm-thrown pitch pines lying around the Island, and note how even on a very small scale, the soil varies in color, texture, and composition.
A wide range of mineral components, varying in chemical composition and prevailing size and shape, translate into a wide range of soil types on the Vineyard. Those mineral components have both shaped and been shaped by the biological activity that has taken place around them. Any particular soil type reflects a complicated synergy between the mineral and biological worlds.
Soils vary in how much water they hold, how quickly water drains through them, how acidic they are, how much organic material they contain, what that material is, what tiny plants and animals live among the soil grains, how they’re situated on the slope, how … well, you get the picture. Those infinite differences translate into localized conditions that favor certain sets of plants and animals over others. From the naturalist’s perspective, a lot of what you notice about wildlife is explained mostly or entirely by soil.
It is the sad lot of soil, however, to be ignored. It’s just there; we never think about how it got there, what’s going on inside it, or how it might be changing. Fortunately, the stuff is resilient. But soils do respond to changes in climate, biodiversity, and human land use; nutrient levels can change, physical structure can alter. Repeatedly across history, human ignorance or indifference to soil have caused ecosystems and economies to collapse.
Especially in the context of climate change and the other ways human activity is now altering the planet’s chemistry, the health of soils is a matter of importance to anyone who likes to eat: Agriculture depends on healthy soils. Soil health also matters for anyone interested in ecology, because relatively subtle changes in the chemistry or composition of a soil can drive surprisingly extreme biological changes. Soil may be commonplace, but it’s as vital as it is complex.
At a free workshop taking place this Saturday, April 7, soil experts from the U.S. Department of Agriculture will address basics of soil science in a morning session, turning to more to agricultural applications of nutrients and soil maintenance in the afternoon. Presented by the Dukes Soil Conservation District, Island Grown Initiative, Polly Hill Arboretum, and the Martha’s Vineyard Agricultural Society, both sessions take place at the Ag Society Hall on Panhandle Road in West Tisbury. Call Bill Wilcox at 508-693-4239 for more information.