Other Environmental Themes

Labors of the Soil

Far more than just ground-up rock, dirt and assorted detritus, soils constitute a vibrant, complex ecosystem that performs invaluable services for the planet. A handful of fertile soil typically contains millions of organisms from hundreds of different species, including bacteria, fungi, algae and protozoa, plus a variety of larger animals such as worms, insects and mites. Collectively, these organisms play a crucial role in getting nutrients to plants, decomposing dead organic matter and neutralizing toxins.

Soils provide shelter for seeds and physical support for plants. They soak up water rained down on the earth and gradually distribute it to plant roots, underground aquifers and surface streams. Microorganisms in the soil are responsible for the decay of organic matter, freeing up essential nutrients and delivering them to plants in a usable form. Soils process an estimated 130 billion metric tons of organic wastes each year, which is how they maintain their fertility and sustain life. Microbial species can also break down some industrial toxins-such as detergents, oils, acids and certain pesticides-rendering them harmless.

On a global scale, soils act as major sources and "sinks" for greenhouse gases. Soils store roughly twice as much carbon and 18 times as much nitrogen than all the Earth's vegetation. Biogeochemical processes within the soil emit about a third of the methane that enters the atmosphere, while also releasing significant quantities of carbon dioxide and nitrous oxides.

It can take hundreds of thousands of years to establish a fertile patch of soil as a result of the weathering of rocks, the gradual accumulation of organic matter and the relentless activities of soil creatures. But this precious resource can be destroyed, or severely impaired, in just a few years. Damage is caused, for instance, by land compaction, contamination from toxic dumping and acid rain, deforestation and overgrazing, which accelerate erosion from water and wind. As a result of human activities in the last half century, soils covering about 20 percent of the Earth's vegetated surface are now measurably degraded.

For too long, soils have been neglected and their role in the environment undervalued. Just as we need to rally to protect our air, water supplies and forests, an equally concerted effort must be made to preserve the thin coat of soil upon which we stand and upon which so much depends.