2. Past: What not to do with dirt

3. Present: On thin ground?

4. Future: Dig in

On this no-till cornfield, crop residue is left on the fields after a harvest to prevent erosion and water loss. Conventional plows are nowhere to be found. Photo by Gene Alexander, USDA.

The United Nations Environment Program recently reported that China's Gobi desert is spreading by more than 10,000 square kilometers per year. The wind erosion and desertification that contribute to this spread result, in part, from large-scale industrial agriculture. In this satellite image of eastern Asia, a large, brownish dust cloud emanating from China is crossing the Yellow Sea, passing south of the Korean Peninsula on its way to southern Japan. Photo: NASA.

The United Nations has published three population growth estimates. To keep pace with the medium prediction (nine billion people by 2050), food production will need to increase by 50 percent in 40 years. If the current trend toward meat-based diets continues, that figure could be much higher.

With current farming methods, it takes about half a hectare per person to provide the rich, high-protein diet enjoyed by Western Europeans and North Americans. Such a diet could not be supported for 6.2 billion: There are only .25 hectares of arable land (land fit for planting crops) per person.

As many as 800 million people remain malnourished and up to three billion have inadequate diets, according to the United Nations Environment Program.

Worldwide, three million kilograms of pesticides are applied each year, but more than 40 percent of food production is lost each year to pests.

Sounds grim, and it would be -- if farmers and governments were interested only in preserving the agricultural status quo. But, says Pimentel, some seeds of change have been planted, and more are on the way.

Down with the plow?
The plow did wonders for crop yields, but for soils it has been more of a blow than blessing. In reaction, conservation methods like no-till farming are growing in popularity. The World Resources Institute reports that in Latin America, for example, no-till farmers operate on 11 million hectares in Brazil, up from one million in 1991. More than nine million hectares of land in Argentina is farmed without tillage, an increase from 100,000 in 1990. As a result, costs for weeding, tillage, herbicides and fertilizers have dropped, boosting profits by up to $200 per hectare (See State of the World 2002, in bibliography).

"No-till works very well, because leaving crop residues on the surface of land protects it from wind and rainfall. It does mean that you have to use herbicides, but if I'm picking between erosion and herbicides, I'll pick the herbicides every day," says Pimentel.

In ridge tillage (one kind of conservation tillage), farmers plant seeds in the valleys between carefully molded ridges of soil. The method prevents some erosion but usually requires the addition of more fertilizer. Diagram: USDA

Perennial hopes
"Some 64 percent of agricultural land in the world is devoted to annual crops," says Wes Jackson, in sharp contrast to "the way the planet was 10,000 years ago, covered with perennials and mixtures. Why is it that nature's ecosystems, over millions of years, have arrived at perennials and mixtures, but people haven't?"

Jackson is trying to change the traditional picture - fields planted with a single crop, which must be harvested and the ground plowed every year -- into cropland that mirrors natural prairies. Using traditional breeding methods, he hopes to convert annual crops like corn and wheat into perennials. The idea is that farmers could leave a crop on the ground for four or five years without plowing, all the while planting mixtures of many crops on one field to keep erosion at bay.

The breeding process takes years, he warns, adding that the Land Institute was founded, in part, as a reaction to the demands of academia. The pressure to publish new results each year simply doesn't work for agricultural research, Jackson says.

The single gene approach of modern biotechnology can't convert annual crops to perennials, he says. "Perennialism is a way of life, and there are probably hundreds of genes associated with that way of life, so getting all of the genes responsible for perennialism and winter hardiness is a huge task,"Jackson says.

" The paradigm we've elected to follow is not like that of industrial agriculture, nor is it that of the organic people or the sustainable agriculture people. Sustainable ag people are forced to deal with annual roots.

"Right now on the organic fields of America, the soil is bare. They won't plant corn for another two weeks. And by June 1, those roots will be two or three inches deep. But the rains are coming and it doesn't matter that they're not using fertilizer or pesticides. The fact is -- they will have soil erosion. Cover crop roots are wimpy," Jackson says.

In the end, agriculture will feed the world only if the world's farmers treat soils with more care than has been shown in the past, Jackson says. The long-term shift he envisions -- perennial crops, fields planted with many kinds of seed, and less reliance on tillage -- may help. But the farmer's ability to make these changes hinges on social, political and scientific support.

Others say sustainable agriculture won't be possible at all, on a planet teeming with people. Finding a way to stabilize the world population at around two billion, Ward Chesworth says, should take priority.

But there is a consensus on one thing, at least: As a species, we should watch where we step.

-- Sarah Goforth

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