The world's most significant environmental crisis, according to farmers, is playing out in the very ground beneath their feet.
The earth's endowment of topsoil - a delicate seven-inch layer of sediment and minerals built over thousands of years - is deteriorating at an alarming rate, even by modern standards of consumption.
In the same time it takes the earth to replenish two-and-a-half tons of soil per acre - about one year - wind and rain erode more than 43 tons per acre in most areas of the third world. It is estimated that one-sixth of the world's soil supply has already been degraded. That fraction will likely grow significantly as farmers turn to marginal lands or their own outstripped fields to feed an additional 2 billion people by 2025.
To avert a global soil crisis, policymakers are attempting to get farmers to pick up their plows - for good.
For 7,000 years, farmers turned up ground to make troughs and seed beds. Their plows have exposed the earth's soil to punishing wind and rain, driving rich nutrients into river beds and untilled ground.
The alternative: A system called "no-till," which leaves the soil and its skin of protective overgrowth undisturbed by slipping seed and fertilizer through a small slit in the ground's surface.
The technique promises to save not only soil, but time and money as well. Unfortunately, advocates admit, the threat posed by no-till to common tradition and local economies could blunt its progress in the third world.
No-till techniques were popularized in the US during the 1980s, when farmers first took significant steps to reduce their depleted surface soil. After harvesting their crop, many US farmers now leave leftover leaves, husks, and grasses on their fields. The residue crowds out weeds, decreasing herbicide costs. More importantly, it provides a protective covering for the top soil, shielding it from punishing wind and soaking in rain water that might otherwise escape.
Since 1982, soil erosion rates in the US have fallen 38 percent, according to the National Resource Inventory.
"By setting the goal of retaining at least 35 percent of crop residue, they've cut erosion to almost nothing," says Edward Deibert, professor of soil science at North Dakota State University.
No-till methods also enable farmers to reduce their workforce and scale back machinery. By not tilling their fields, they need take only a few passes through each crop row, rather than five to 10.
The ecological and financial benefits have drawn the attention of policymakers.
Later this month, officials from the World Bank, which began to aggressively promote the technique a few years ago, will visit successful no-till operations in South America, where Argentina and Brazil have used the technique to plant a total of 57 million acres.
Their harvests have born an unexpected boon: Water efficiency is up 40 percent. In the Pampas region of Argentina, for example, the untilled soil conserved an average of four inches of usable water each year.
"The cover crop absorbs raindrops and allows it to flow into the soil rather than letting it run off," says Dan Towery, a natural resource specialist at Purdue University in West Lafayette, Ind.
In 15 years, the water savings will be required to meet the needs of booming populations in China, India, and Pakistan - each of which is experiencing severe groundwater depletion after nearly 50 years of heavy irrigation.
No-till methods might not take root outside the Americas, however. Most farmers, many of whom still use livestock for plowing, would require a substantial subsidy to pay for new seed drills. In many cases, farmers would not leave crop residue on their fields, preferring to use it for housing, animal feed, or to burn for heat. And the need for less labor could seriously disrupt local economies.
The primary obstacle, like in all shifts in a community's way of life, could be a simple reluctance to change.
"The basic issue is that this requires trust that what you will start doing will work as well as previous techniques," says Raymond Hopkins, a professor of political science at Swarthmore College in Swarthmore, Pa.