On a warming planet, humanity faces a great challenge in feeding itself at reasonable cost in the coming century, as I explain in Sunday’s paper. An issue I raise only in passing in the article is that agriculture itself is one of the earth’s greatest environmental threats.
To put a finer point on it, farming and livestock grazing are not just potential victims of climate change — they are major causes of it.
Humans are cultivating almost 40 percent of the land surface of the earth, and nearly a third of all the greenhouse gas emissions that are warming the planet comes from agriculture and forestry. Those emissions are linked not only to the factors that many people tend to think about, like the fossil fuels burned in transporting food; that, in fact, is only a minor source of emissions.
Nitrogen fertilizer, though essential to producing food for seven billion people, is one large source of emissions, and not only because it requires natural gas to produce. After it is spread on farmers’ fields, a portion of it turns into a potent greenhouse gas that escapes into the atmosphere. (As many people know, some nitrogen also washes into rivers and streams, ultimately making its way to the ocean, where it contributes to dead zones at the mouths of many of our great rivers, including the Mississippi.)
The biggest of all the ways that agriculture contributes to climate change, though, is the chopping down of forests to make way for farms and cattle grazing. The world’s forests are enormous stores of carbon dioxide, and when they are cleared, the vegetation that is burned or allowed to decay oxidizes into carbon dioxide, the major greenhouse gas. In recent years, changes in land use have accounted for some 25 percent of the carbon dioxide being emitted on the planet, and the bulk of those changes are driven by agriculture.
As my colleague Elisabeth Rosenthal has reported here and here, efforts are under way to slow deforestation. But scientists say that alone will not be enough. Somehow, even as humanity increases the production of food over the coming decades, it must reduce the environmental footprint of agriculture. The alternative is continued ecological degradation and a worsening of climate change, which in turn would make food production harder.
When you view the problem in that light, the challenge of feeding ourselves becomes that much larger.
I visited the International Maize and Wheat Improvement Center in Mexico in February, near the end of the wheat-growing season. This institution was the original starting point for the Green Revolution, which raised agricultural output across much of the planet.
While it saved humanity from mass starvation, the Green Revolution has often been attacked on the left for having spread environmentally unsustainable practices to developing countries. Most agronomists now acknowledge that it did, in fact, cause many environmental problems, although they contend that these have sometimes been exaggerated, and were in any case necessary at the time to prevent famine.
Perhaps it will come as a surprise to many to learn that the sustainability of agriculture has become a major focus at the International Center for Maize and Wheat Improvement.
The director general, Thomas A. Lumpkin, told me that the real task at hand was not just to increase food output, but to make agriculture so productive that humanity could begin to restore some of what it has destroyed.
“We need to be really bold here,” he said in an interview. “It’s not just that agriculture needs to keep food prices reasonable. We need to find a way to make a dramatic contribution to the greenhouse-gas problem. We need to make farming so productive that we can get off half the agricultural land out there, so that we can return it to nature.”
That is a tall order indeed, and how it might be done is not clear. But the center in Mexico, like many other institutes around the world, is exploring various strategies. One approach, known as conservation agriculture, has begun to gain some traction. It involves minimal tillage of the soil, leaving straw and stubble in place as a soil cover, and various other techniques that conserve water and nutrients and allow carbon to build up in the soil.
In some ways this approach resembles organic farming of the sort that has caught on in the West. But it differs in that farmers are still allowed to use inorganic fertilizers and to make judicious use of herbicides. “I’m not for or against organic agriculture,” Bram Govaerts, one of the researchers in Mexico who is studying this method, told me when I visited. “I am for rational agriculture.”
Conservation agriculture has not been proven to work in all farming scenarios, and even when it does work, yields sometimes fall during the initial changeover period. It can require new machinery, a barrier for many farmers. But in many places, after a transition of several years, the method has been shown to increase organic matter in the soil, raise yields, lower costs, increase resilience to drought and other stresses, and reduce the use of nitrogen and water.
Technology adapted to the needs of small farmers may be able to help. When I was in Mexico, I met Jared Crain, a student at Oklahoma State University. He was working to improve a hand-held sensor that uses the color of plants to tell when they need nitrogen fertilizer.
Such machines are available in the West for thousands of dollars, but the one Mr. Crain was working on might sell for $200 or so, making it accessible to villages or to agricultural extension agents in developing countries. The idea is to cut the excessive use of fertilizer that is common in many of the areas touched by the Green Revolution.
As conservation agriculture becomes more advanced, improved crop varieties are likely to be an important part of the picture. Gary Toenniessen is director of agricultural programs at the Rockefeller Foundation, of New York, which provided the original funding for the work that led to the Green Revolution. “The Green Revolution varieties were ecological weaklings,” he told me in an interview. “They had shallow roots, short stems and couldn’t compete with the weeds. They needed tender loving care from the farmer. Given tender loving care, they put all their energy into grain production.”
The task now for plant breeders is to preserve and enhance the yield gains of the Green Revolution, while creating varieties with deeper root systems that can survive on less water and fertilizer and are also strong enough to germinate through a dense cover of decaying vegetative material from the previous season.
Conventional breeding can accomplish some of that. But many experts say the biggest gains will eventually come from the genetic engineering of crop varieties. For example, Monsanto is on the verge of winning approval for a transgenic corn plant designed to protect crops from moderate drought; a project is under way to make that trait available to African farmers.
Such varieties could presumably be employed in irrigated agriculture as a way to cut down on water use; and in the future, transgenic varieties might allow lower use of nitrogen fertilizer, directly tackling one of the major sources of greenhouse gases from agriculture.
As such approaches become more widespread, I am guessing that critics of crop biotechnology will face a choice: Do they embrace technologies that violate their ideological precepts but offer potentially big environmental gains, or do they continue to oppose them?
In fact, among many of the experts I interviewed, I detected a great weariness with the ideological battles that have surrounded the food system in recent years. Like it or not, they said, the reality is that the agricultural system is only going to get more intensive as the human population rises and diets grow richer.
“We’re not going to be abandoning conventional agriculture,” said Jonathan A. Foley, a University of Minnesota scientist. “So why don’t we fix it?”
