The dirt on soil loss
By Andrea Baird

Dirt gets no respect. We buy “dirt-cheap” used furniture at garage sales and punish our kids for ogling “dirty” magazines. But while we are buying, ogling, and punishing, dirt is keeping us alive. “[Soil] is the source of the energy and materials that made us,” says Ward Chesworth, an adjunct professor in the Land Resource Science department at Ontario’s University of Guelph. “We are a crop of the soil just as much as wheat or barley.” More than 99 percent of human food grows on the land, all of it rooted in the soil. But through erosion and degradation, we loose more and more soil everyday. As the soil recedes, a crisis looms.

Twenty-one percent of the world’s cultivated land is now so severely degraded that it is no longer fertile. It’s not a new problem; soil loss has plagued us since humans cultivated their first crops 10,000 years ago. Some of history’s earliest farmers, growing crops in southern Turkey, built flat terraces for planting so that rain wouldn’t wash the soil down the hillsides of their mountainous terrain. Today’s farmers have six billion mouths to feed, and increasing population has made soil loss a problem on a global scale.

Fertile soil can be lost in several ways. Most commonly, it is dragged off the land by erosion. When farmers loosen their fields by plowing or leaving bare land unplanted, wind and water are free to wear away the dirt. The farmer is left with nutrient-depleted soil, and less of it. “When you have soil erosion, you lose topsoil which tends to be the most fertile,” says Chi-Hua Huang, a soil scientist at the U.S. Department of Agriculture’s National Soil Erosion Research Lab.

Soil is also spoiled when salt concentrates in the upper layers of routinely flooded or over-irrigated land. When soil is saturated, salts that naturally occur deep in the land diffuse upward. Grains and corn – our primary food staples – can’t grow in salty soil. Once soil is ruined by salinization or removed by erosion, it can’t easily be replaced.

Soil erosion and degradation cause a host of problems that grow along with exploding populations in the world’s poorer nations. “In developing countries the loss of soil can cause significant amounts of productivity decrease,” says Huang. Poverty exacerbates soil loss by forcing people to strip away every scrap of plant material their land can produce. Farmers in sub-Saharan Africa harvest not only the fruits of their crops but the plants’ stalks and roots, because they can’t afford other fuel for their fires. Their cows and goats, lacking other feed, graze the few plant scraps left in the field. With no organic matter left to decompose and return nutrients to the soil, the land becomes sterile. And with no plant roots left to hold it down, topsoil is whipped away by wind, further reducing soil fertility and even causing breathing problems and lung disease. The depleted soil yields fewer crops, and the cycle of poverty perpetuates itself. “These poor suffering people pass on their suffering to the land,” says Rattan Lal, a professor of soil science at Ohio State University.

Similarly, in the Brazilian rainforest, Amazonian Indians must slash-and-burn trees to plant crops. The bared topsoil quickly washes into the Amazon River. Now, “rock is exposed in places where there was forest,” says Farouk El-Baz, the director of Boston University’s Center for Remote Sensing. The Amazonians, like the farmers in sub-Saharan Africa, must either clear more land or join the estimated 800 million chronically malnourished people in the world.

For wealthy countries like the United States, malnourishment from soil loss is not a major concern yet, but the erosion of soils poisoned by chemicals is. “In developed countries we can put in more fertilizer to bring crop yield up – it’s more of an environmental issue,” says Huang. When eroding soil blows or washes off a field into a nearby river, it may be laden with pesticides, herbicides and fertilizers. The soil muddies clear streams, the fertilizer causes algal blooms, and herbicides and pesticides can kill aquatic animals. Contaminated soil washing down the Mississippi River from Midwestern farms fuels plankton blooms that cause a huge yearly “dead zone” at the mouth of the river, crippling shrimpers.

But farmers are combating soil loss. Soil erosion has been reduced by 40 percent in the United States since 1982. The federal Conservation Reserve Program alone saved twenty million acres of fragile cropland by paying farmers not farm it. Other farmers continue to grow crops on their land but simply stop plowing – a technique known as “no-till” farming - effectively reducing erosion while allowing nutrients to build up in the soil. “I know [no-till] farmers who claim they out produce their neighbors by 15 percent,” say Edward Skidmore, research leader at the USDA Agricultural Resource Service’s Wind Erosion Research Unit. The Land Institute, an agricultural research group, is crossbreeding major annual food crops like corn and wheat with wild grasses to produce perennial plants that would never need tilling and only rarely need replanting. The first of these crops, whose 18 foot roots would anchor soil better than shallow-rooted annuals, are still in the experimental phase. But planting existing perennial crops, like alfalfa, is a viable option for farmers with erosion problems. “It is a good alternative, especially on fragile lands,” says Larry Mitchell, the CEO of the American Corn Growers Association.

Genetically modified crops have also been put forward as a solution to soil loss, and they offer many advantages. Herbicide resistant crops, like Monsanto’s Roundup Ready soybean, allow farmers to spray crops liberally with herbicide instead of plowing weeds under. Crops that have been genetically engineered for salt tolerance have the potential to not only grow in salt-ravaged soils, but to absorb the salt from them, renewing their fertility. GM crops are controversial, however, because of their unknown environmental effects and because they are often engineered not to produce seeds, forcing farmers to buy new seeds each year from the corporation that developed the crop.

But no matter the advantages, GM crops and new farming techniques cost money to implement, something third world farmers don’t have. Increasing soil loss in these countries, and the poverty and hunger that result, goes largely unchecked because it “happens in places that the world is not interested in,” says El-Baz. One major roadblock is that people don’t know about the issue. “There are efforts to make policy-makers aware of this problem,” says El-Baz. “What I don’t see is an international effort to help people.” Getting assistance for people whose land is dying around them is going to require a major effort from an international organization like the United Nations, Lal says. “It’s going to take trillions and trillions of dollars to set the earth back the way it should be,” he adds. “But it’s doable.”