What makes soil, soil?


From the time of his first trip to Antarctica in 1969, Jim Bockheim says he always considered the “weathered, surficial deposits” on the continent to be soils. But when the University of Wisconsin professor submitted one of his first papers on Antarctica’s soils to the journal Geoderma in 1982, the editor Roy Simonson warned Bockheim that others might not agree.

A sandy Antarctic soil with a spade in it

“He was a very wise man,” Bockheim says, “and he wrote to me that I needed to give a working definition of soil in my paper because a lot of people weren’t going to be convinced that they really were soils.”

So after consulting the literature, the soil scientist put together his thoughts. Soil, he wrote, was any surface material composed of solids, liquids, and gases that showed visible signs of weathering and was organized into layers or “horizons.” In the end, the new description wasn’t much different from older definitions except in one significant way: Bockheim removed the requirement that soil support higher plants.

Soil taxonomy is a practical system, Bockheim explains, focused on the potential uses of soil. For example, soils are described and classified to help assess whether the ground can support a building or road, house a septic system, or produce crops or forests. That’s why some scientists objected to calling Antarctica’s surface deposits “soil.” All they seemed capable of growing were microbes, mosses, and a few other lowly life forms.

Still, Bockheim’s definition was accepted and published by Geoderma, and then in 1992, his work caught the attention of the Soil Conservation Service (now, the Natural Resources Conservation Service). Having recently grown interested in soils of the polar regions, the agency was intrigued by his ideas on revising the U.S. soil classification system to better accommodate them—especially those in Antarctica. In 1994, Bockheim was asked to lead the International Committee on Permafrost-Affected Soils. Three years of intense debate later the committee established a 12th soil order specifically for permanently frozen soils: the Gelisols.

What’s more, when the agency revised its formal definition of soil in 1999, it adopted Bockheim’s definition from 1982. No longer would any soil have to support higher plants to be worthy of the name.

Bockheim is glad Antarctica’s soils are “official” now, and he’s proud of his role in getting the Gelisols recognized. He also thinks it was all pretty inevitable.

“The point is that there are soils in Antarctica, which are 11 or 12 million years old and are very strongly altered,” he says. “So if we didn’t call them soils, what would we call them?”



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