The hidden world under our feet

The worrisome decline in biodiversity is well known. Experts say that by 2100, half of all the world’s plant and animal species may disappear. Yet one of the most important threats to biodiversity has received little attention — though it lies under our feet.

Over the last decade, scientists  have found that the world’s ocean of soil is one of our largest reservoirs of biodiversity. It contains almost one-third of all living organisms, according to the European Union’s Joint Research Center, but only about one per cent of its micro organisms have been identified, and the relationships among those life-forms is poorly understood. Soil is the foundation on which terrestrial biodiversity is built.

To know more, scientists recently embarked on the Global Soil Biodiversity Initiative to assess what is known about soil life, pinpoint where it is endangered and determine the health of the essential ecosystem services that soil provides.

They are not just looking at soil in remote, far-off landscapes. One of the more
intensive studies is taking place in New York’s Central Park. The focus is on the life that resides in the soil — the microbes, fungi, nematodes, mites and even gophers that make up a complex web of interrelationships. A teaspoon of soil may have billions of microbes divided among 5,000 different types, thousands of species of fungi and protozoa, nematodes, mites and a couple of termite species.

“There’s a teeming organisation below ground, a factory, with soil animals and microbes, each with their own role,” said Diana H Wall, a professor of biology at Colorado State University who has studied soil biodiversity in Antarctica and Kansas over the last two decades and who is the scientific chairwoman of the soil biodiversity initiative.

The last decade of research has overturned a key concept. For decades there was a saying among soil scientists — “everything is everywhere,” which meant that soil was largely the same across the globe. That has proved to be spectacularly untrue.
A 2003 study in the journal, Ecosystems, estimated that the biodiversity of nearly five per cent of the soil in the United States was “in danger of substantial loss, or complete extinction, due to agriculture and urbanisation,” though that was most likely a very conservative guess, since the planet’s soil was even more unexplored then than today, and study techniques were far less developed.

That means that species critical to some important functions could have already disappeared or be on their way out. Modern tillage agriculture is a big threat, because it deprives soil life of organic matter it needs for food, allows it to dry out and adds pesticides, herbicides and synthetic nitrogen. Soil “sealing” from the asphalt and concrete of suburban sprawl destroys soil life, as do heavy machinery and pollution. In nearly half of Africa, for example, overgrazing and intensive agriculture has destroyed topsoil and led to desertification. Yet few things are more vital than healthy soil life. Our food supply begins in the soil.

Healthy soils also hold the cure for some diseases. Scientists are searching soil in various places now for a new class of antibiotics to deal with antibiotic-resistant diseases.

New technologies that enable scientists to study the genes of soil microbes and to track microscopic amounts of carbon and nitrogen as they pass through the soil ecosystem have provided leaps in the understanding of soil ecology.