Agriculture versus Biodiversity

By Richard Manning

Illustration ©Dave Cutler/SIS

There’s a good reason that the central organizing myth of agriculture is man against nature. Throughout much of the 10,000-year-old experiment that is farming, observers from Plato to the present have lamented what George Washington called farming’s “baneful effects.” The tenor of that litany is best summarized by Aldo Leopold’s harsh assessment in Round River, published in 1953: “As for diversity, what remains of our native fauna and flora remains only because agriculture has not got around to destroying it.” (1)

Since Leopold’s time, though, there has been a sharp escalation in industrial agriculture—the shorthand term for which is the Green Revolution. Largely driven by the work that won Norman Borlaug a Nobel Prize in 1970, the revolution was based in wheat and rice and relied heavily on synthetic chemicals, especially chemical fertilizers—and especially nitrogen and phosphorus—to achieve a miraculous leap in crop yields that staved off starvation a generation ago. Although the effects of the revolution range from pesticide pollution to freshwater depletion, energy consumption, erosion, and salinization, we can nonetheless use a single element—nitrogen—to trace the revolution’s swath on the planet.

Now, in a unique corner of Mexico’s Sonoran desert, researchers have spent seven years testing market solutions to halt nitrogen damage in the developing world. Their experience suggests that the challenge is far more complex and unpredictable than anyone expected. They are trying to hit a moving target.

The project began as a two-week-long brainstorming session at a global change workshop in Aspen, Colorado, in 1992. The intensive discussion about global change led to agriculture, and the discussion of agriculture led to nitrogen, says Rosamond Naylor, an economist and a senior fellow at Stanford University’s Center for Environmental Science and Policy. At the conference, she hooked up with ecologist Pamela Matson, then at the University of California at Berkeley, making for an interdisciplinary collaboration from day one—a key element in the unwinding of this story.

Now, Matson is at Stanford, and the project includes not only economists and ecologists but also agronomists, engineers, geologists, hydrologists, climatologists, biogeochemists, political scientists, and geographers. They are combining efforts to model and measure the links among the social, biological, and physical flows of the Yaqui River Valley. The project has grown to a $2-million-a-year effort to intensively study how world agriculture threatens biodiversity. In the beginning, though, it was a simple proposition to test a relatively simple and powerful tool, the use of a market solution—price—to curb nitrogen pollution.

It seems natural, if for nothing more than symbolic reasons, to focus research on the effects of the Green Revolution on a town where a major road is called Avenida Borlaug. Mexico, like most of Latin America, names its main streets for heroes, and in Ciudad Obregon, Borlaug is exactly that. Unlike most of Mexico, the arid Yaqui River Valley surrounding Obregon doesn’t have an agricultural history that stretches back to Aztec farming. Instead it was colonized only in modern times by large-scale commercial farmers. They grew wheat. Borlaug settled on the valley to do some of his initial breeding work in 1944. That is to say, the valley was ground zero for the Green Revolution. Seed from the wheat varieties Borlaug bred there were exported directly to South Asia, which became the revolution’s second front. The Yaqui was and still is a leading edge, a predictor of the shape of developing world farming.

The valley was a solid predictor of the nitrogen boom. Farmers in the Yaqui Valley make their counterparts in the American Midwest look like nitrogen misers, usually applying about 250 kilograms per hectare of land, more than double the U.S. rate. Average rates vary widely around the world, from a low of 10 kg/hectare in sub-Saharan Africa to a regional high of 216 kg/hectare in East Asia. The world average is 83 kg/hectare. Globally, the trend in the growth of fertilizer consumption is weighted toward the developing world, largely because Green Revolution methods emphasized fertilizer production and spawned a series of government subsidies and investments. In 1960, the developing world accounted for 12 percent of all nitrogen consumption; today that figure is 60 percent. The developing world has already overtaken the developed world in its ability to replicate the Gulf of Mexico’s Dead Zone (see box on opposite page).

The connection to water was the second key element in the researchers’ choice of the Yaqui Valley. It is an island of 225,000 hectares of irrigated agriculture surrounded by desert, by and large a single watershed formed by the Yaqui River. It is heavily irrigated by old-fashioned flood irrigation, creating a network of nitrogen flows. All of this drains to the Sea of Cortez, itself a relatively discrete system, but also a vital web of estuaries, tidepools, mangroves, and marine life. Yaqui made sense because the problem was well-defined, the scale was graspable, and the threat to a marine system was clear.

“We began thinking about this as a place that could go down the tubes,” says Matson. “Anoxia drives off anything that can swim, and it kills everything else.”

Matson and Naylor teamed up with Ivan Ortiz-Monasterio, an agronomist at the International Center for Improvement of Wheat and Maize, or CIMMYT, its Spanish acronym, in Mexico City. CIMMYT is the institutionalization of Borlaug’s work, and a CIMMYT field station is located in the Yaqui Valley. The three began testing an idea.

Agricultural nitrogen, unlike most pollutants, is not a byproduct of an industrial process. It is a purchased input. The nitrogen that makes it into waterways as runoff is waste, an asset that got away. Field trials in the U.S. have shown that typically 50 percent and sometimes as much as 70 percent of the fertilizer applied simply leaves as pure waste. The researchers put together trials to measure that waste as it accrued under the specific conditions and practices of the Yaqui farmers, comparing their methods with simple alternatives that timed application of nitrogen with stages of plant development and the irrigation cycle. The idea was to conserve fertilizer by applying it when the wheat would most readily absorb it, thus avoiding runoff.

The researchers concluded in a 1998 paper in Science that alternative practices designed to conserve nitrogen could cut fertilizer use to 180 kg/hectare compared with the 250 kg typically applied by farmers—and at the same time cause no decrease in crop yield. (2) The reduction was in waste, which meant that the alternative practices greatly reduced nitrogen flows both to the atmosphere and to streams. The bottom line was a 12-17 percent increase in a farmer’s net profit (see table on opposite page). To a conservationist, this is not so much a number as a tool, the elusive win-win.

This sort of market solution is of particular concern to those who work in the developing world. The U.S. has a long history of regulating pollutants but is still hard-pressed to regulate nitrogen runoff from farms. Farms are notorious non-point sources, diffuse and difficult to control. It’s worse in the developing world where lax, ineffective government on the one hand, and the ubiquity of hunger and poverty on the other, make governments even less likely to jeopardize grain yields. Enter the unseen hand of the market, the economic carrot to replace regulation’s stick. The investigators quickly found out they had a testable market solution to an environmental problem, so they tested it.

Researchers conducted a long series of meetings with prominent farmers. They set up field schools and demonstration plots and pamphleteered in a multi-pronged effort to spread the glad tidings. The effort self-consciously targeted a cross-section of farmers, ranging from U.S. to 20-acre dirt farmers to dirt-poor cooperatives called ejidos, which account for about half of the valley’s farmers. The message was tailored in content and delivery to each social stratum.

In the spring of 2001, Naylor, Matson, Ortiz, and I visited some of these same farmers. We went into the field expecting to find a payoff for the years of demonstrating the economic advantages of the clear market solution, especially because the price of fertilizer —the costliest element of a farmer’s annual investment—had suddenly increased by 50 percent. Conservationists in the U.S. have suggested that a relatively modest tax on nitrogen can stem its flow, so the Yaqui Valley was offered an extreme test.

Juan Dorame has a simple little farm smack in the middle of the Yaqui. We walk his neat field of raised beds for durum wheat as he details for us with some pride his bounty yields, which are accomplished with less irrigation water (read less runoff) and, on average, about 20 percent less nitrogen than the norm. Oritz uses some of Dorame’s fields for trials, making for a clear demonstration to his neighbors. Dorame tells us through an in-terpretor how he has invited his neighbors—over and over again—to come to his fields, to literally count every stalk in a square meter and to weigh every seed head to demonstrate his yield. Their response? They don’t believe him and change not a thing on their own farms.

“It’s hard to change these people,” he says. “They think it is not necessary to change what they have done for twenty years.”

Jorge Castro runs his family’s farm of 250 hectares, big by the valley’s standards. He is an innovator, has allied with a couple of neighbors to found a research organization, and is experimenting with marketing his own brand of seed maize. He grows safflower, soybeans, potatoes, and, of course, durum wheat. He practices conservation tillage, which reduces runoff. He and his banker have begun to think in terms of maximum economic yield, which is to say he will accept some decline in his yields as long as the reduced costs maximize profit. This sort of thinking and Ortiz’s demonstrations have allowed him to cut nitrogen rates from 250 to 180 kg/hectare.

So here is a bellwether farmer, one whose practices can be counted on to provide the example that will sway neighbors. We ask Castro about this. He shakes his head for a moment and fiddles with his cell phone. Agronomists spread the word by holding field days, when neighboring farmers are invited to see the profitability of alternative practices. “We have held many, many, many field days,” he says through an interpreter. “There has been no impact. This culture is deep-rooted. It is hard to change.”

Enrique Orozco Parra is not just a farmer with 500 tilled acres under his control. He was, when I interviewed him in the spring of 2001, also president of the Patronato, an organization to which every farmer in the valley belongs and which is responsible for research, innovation, and information. A conversation in his office runs from water use to subsidies, global markets, and capital costs. He has a solid command of it all. And yes, he has heard that he can reduce fertilizer use and not reduce profit, has seen the test plots, and, yes, the 50 percent price increase has been a terrible burden. All of this he understands as well as any businessman.

So how has he responded on his own land? No change. In fact, sometimes he lays down as much as 300 kilos of nitrogen per hectare, an amount off the global scale. He tells us nitrogen is cheap insurance.

Walter P. Falcon, a senior professor at Stanford’s Center for Environmental Science and the eminence grise of this project, chuckles a bit on hearing this conversation. Falcon was raised on an Iowa farm; his brother still farms. He says Orozco’s answer doesn’t surprise him; he can imagine his own father saying the same thing. Farmers worldwide have been urged for generations to try new ideas. They’ve heard it all, just as they have watched many neighbors go broke from trying new ideas. The experience builds an inherent conservatism, an obdurate allegiance to the notion that one does not fix what is, from their point of view, not broken.

All of this is, of course, anecdotal, so after our visits, Ortiz followed up with a survey of farmers. After five years of work, no change. The Sea of Cortez is bearing the same burden as always—in fact, as we shall see, probably worse. The researchers take a deep breath and remind themselves that a negative result is still a result. So where do we go from here? Researchers have a couple of ideas.

First, both Falcon and Ortiz don’t believe that seeking an economic solution is a dead end, but it will require more sophisticated analysis than simply considering price. For instance, during some of the surveys and interviews in the valley, researchers found that farmers were heavily attuned to lenders’ conditions for credit and that lenders were the real conservatives, in that they were specifying outdated nitrogen practices as a condition for loans. If true, the lenders have leverage, so researchers have decided to see whether it can be used.

Beyond this, though, the failure of the simple mechanism of price has caused researchers to reach further: to politics and analysis of information flow, to fundamental questions of how and where farmers learn. In the fall of 2001, serendipity handed the researchers a way of testing the roles of political power and information. Jorge Castro, the progressive farmer, succeeded nitrogen profligate Enrique Orozco as head of the Patronato, making for a test of the power of leadership. The work goes on.

Monoculture is not just a problem for nature; a lack of diversity threatens farmers as well, especially when pacts like the North American Free Trade Agreement plunge farmers into global markets and especially when an entire valley relies on a single crop like wheat for most of its income. The farmers of the Yaqui understand this better than anyone, so they are using their access to markets as well as capital generated by past development to diversify. In this case, increasing sophistication and diversity of production define development. This is what makes the Yaqui a moving target.

Expect this trend in the rest of the developing world as well. Is this a good thing? It can be when, for instance, farmers diversify row crops into something like chickpeas, as many are doing. Because chickpeas are a legume, they fix free nitrogen from the air, which cuts back on the need for synthetic nitrogen applications—at least on paper. But in interviews, farmers said they regarded this as simply a shift to another crop and were not taking advantage of thoroughly planned rotations to reduce nitrogen applications. Nor have agronomists in the Yaqui Valley developed such systems, a failure that undermines nature’s fundamental relationships. Ortiz says experiments have demonstrated that legumes actually decrease their rates of fixing free nitrogen from the atmosphere in response to synthetic nitrogen fertilizer in the soil, so in the Yaqui’s environment, a potential solution becomes another problem.

More significant, however, is the more widespread diversification into livestock and aquaculture, both an increasing presence in the valley. The former is attractive to farmers because it provides a huge sink for surplus grains, a sort of value-added operation that turns surplus grain into meat readily snatched up by global markets. There is an ironic lesson here. Ostensibly, the Green Revolution boosted yields to feed the poor, but as its successes leave the world awash in cheap grain, the tendency is for that grain to go to livestock that feeds the world’s rich an ecologically costly diet. Further, grain-fed livestock operations tend to look like nitrogen factories.

Miguel Olea walks us through his 6,000-sow hog farm, a typical confinement operation. The brood animals are penned in spaces no larger than their Harley-Davidson-sized bodies. The hogs face a constant stream of feed on one end and send a constant stream of nitrogen-laden manure out the other. Because of inefficiencies in the way they process food, a typical hog will produce more than double the waste of a human in one day. A hog farm of 6,000 sows and their young produces as much untreated sewage as a sizable city does. Olea’s sows produce about 100,000 young hogs for slaughter each year, feeding a market that is globally stratified. That is, the expensive cuts like loins ship to Japan; the cheap cuts stay in Mexico.

Out back of his massive steel barns, a simple slit of a drainage ditch carries a steady stream of manure slurry as egrets wade in it for an early cut of the nutrients. In the best case, this nitrogen-rich stream flows to fields, displacing synthetic nitrogen (Olea’s does). But this manure also runs off in storms and after flood irrigation to join the stream bound for the estuary. In the worst case, those manure ditches go straight to drainage ditches and the sea. Already there are about 30,000 sows in the district around Ciudad Obregon, 103,000 in the whole state of Sonora. Falcon says Olea’s operation is exemplary, unusually well run. He worries though, that as the hog industry spreads, the new operations will be far worse.

One can follow the drainage canals as they parallel the flat valley’s straight roads to head for Tobari Bay and the Sea of Cortez. Along the way, one notices not so much hogs, but everywhere billboards with banks offering to finance shrimp farming. This is the more significant track of diversification, driven by a huge demand for shrimp in Europe, the United States, and Japan.

Worldwide shrimp farming has become an explosive threat to biodiversity, largely because it operates at such a high trophic level. Shrimp eat protein, fishmeal vacuumed from marine sea webs by factory trawlers. Further, in Southeast and South Asia, Latin America, and increasingly Africa, these farms are located next to estuaries, usually in mangroves. Locally these are regarded as scrub land, but they are the key to the productivity of tropical estuaries. The farms concentrate nutrients and disease, providing an effluent enriched not only with nitrogen but also with phosphorus, fungal diseases, and the antibiotics that are routinely fed to the shrimp. The area of Mexico surrounding the Sea of Cortez now holds at least 26,000 hectares of shrimp ponds, sending about 3,000 tons of nitrogen to their waste streams annually. Potentially, though, these numbers could explode by a factor of ten.

The best way to get some sense of the scale of this threat is to walk a 1,000-hectare shrimp farm, one of several now winding around the valley’s coast. The flat landscape is completely stripped of any sort of vegetation, diced into 10-hectare “tanks” which are simply rectangular ponds held by bulldozed berms. Each hectare will produce more than two tons of shrimp. There is an intake canal pulling salt water from the sea two kilometers away. Eight 250-horsepower diesel pumps suck saltwater to the ponds. There is a discharge canal sending effluent back at the same rate.

The managers of this operation, a cooperative that includes eleven local ejidos, make a point of telling us they have carefully located the farm inside the ring of mangroves. This is true. But as we walk the outlet canal and flush a juvenile heron, egrets, kingfishers, and pelicans, we also notice that the canal cuts straight across a tidepool, effectively damming tidal flows from a mangrove area easily the size of the shrimp farm. All of the mangrove trees in this stretch are dead. The canal discharges straight to a mudflat that is shiny with algal slime at low tide. We can hear the cacophony raised by the shorebirds and migratory waterfowl that depend on this key section of the Pacific flyway—but in the distance. The canal has washed old tires downstream with the rest of the effluvia, and they stand upended in the mudflats, planted like tombstones.

Paredoncito is a fishing village, just coming awake on a sunny morning in January. Kids head toward school while women sweep the dirt streets and chickens scratch and peck. We stop and speak with Bernal Guadalupe, a fisherman in this village since 1970. He catches the estuary’s native shrimp or crab or local fish. On a good day, he sells his catch for enough to buy a day’s worth of gas for his boat and food for his house. A year before our visit, Paredoncito fomented a significant event, and Guadalupe wants to show us the scene. He climbs in our beat-up Suburban, and we bounce the back roads for a couple of kilometers to a broad, flat stretch of bermed shrimp ponds. This was to be a shrimp farm, but it lies dry and abandoned. Guadalupe and his wife, Marialena Garcia, take us to the discharge canal to show us why. They describe the day when all the people in the village and several neighboring fishing villages marched to the canal and filled it in by hand.

He tells us the villagers understood that the shrimp farm would harm the native fishery. He’s right. Shrimp farming kills shrimp. So they stopped the farm. The protest/dig-in brought police. Such matters are taken seriously in the Yaqui; there has already been a murder stemming from confrontations between fishers and shrimp farmers. The villages had tried to stop the farm through more formal action, but that failed to get the government’s attention. The protest did, though, and the government pulled the shrimp farm’s permit.

We have come full circle now, in that researchers went into the Yaqui looking for a market solution for the spreading footprint of development, partly because in the developing world, regulation is difficult. Their early, negative result has not ruled out the role of markets but has re-directed the research toward more finely honed solutions. Ortiz is now working to develop a set of on-farm diagnostic tools that can be used by farmers to see for themselves exactly how much nitrogen is needed on a specific field, a signal more immediate than price.

Meanwhile, Falcon says the market still will play a role, but researchers need a more complex vision of the market. For instance, farmers must borrow money, and often bankers insist on certain levels of fertilization as a condition of loans. So the researchers have begun broadening the investigation of the valley’s chain of information, looking for leverage points in other corners of the market.

Still, there is also little doubt that the shrimp farm near Paredoncito was regulated, not marketed, out of existence, but that doesn’t rule out the role of solid information. Naylor says the sort of detailed data built by the researchers so far goes a long way toward arguing for and fine-tuning regulations. That is, legislators prone to rely on market solutions now can see a thorough test of that idea, as well as some clear examples of how market forces can dovetail with regulation. Clearly, there is a carrot in the market, but it may need to be used in conjunction with the regulatory stick.

For Matson and Naylor, the lesson here was that what researchers first thought simple and graspable is in fact complex. This has led them into a multi-disciplinary program and alliances not only with economists and political scientists but also with a local environmental group, Pro Natura, and the World Wildlife Fund. From the very beginning, the researchers meant for that interdisciplinary foundation to be real. Naylor, the economist, learned to run a gas chromatograph to analyze nitrogen samples. Matson, the ecologist, went on interviews for sociological surveys. Both learned to think about the issues facing Yaqui farmers in a completely different way

Naylor says the downside of this approach was that funding institutions are not yet used to thinking across lines of discipline, so it was very difficult to piece together the grants to pay for the work, but they did. The upside, though, has been the gain in understanding of the pushes and pulls of power that run the Yaqui Valley. That in turn has allowed conservationists to identify alliances such as the one that has formed between the fishing villages and the environmentalists. There are, in fact, balancing economic interests to those of the farmers, interests that coincide with protection of the health of the Sea of Cortez. These counter forces can be the basis of coalition politics, which is to say, social and economic diversity may well be a tool to protect biological diversity. Markets are but a single thread of the more complex social fabric.


In addition to those named, this article relied on information, legwork, and advice from Amy Lynd Luers and John Harrison, both of Stanford University.

Literature Cited

1. Leopold, L.B. ed. 1953. Round River: From the journals of Aldo Leopold. Oxford University Press, New York.

2. Matson, P.A., R. Nayor, and I. Ortiz-Monasterio. 1998. Integration of environmental, agronomic, and economic aspects of fertilizer management. Science 280(5360):112-115.

3. Vitousek, P.M et al. 1997. Human alteration of the global nitrogen cycle: Causes and consequences. Issues in Ecology Number 1.

Suggested Reading

National Research Council (U.S.) Committee on the Causes and Management of Coastal Eutrophication. 2000. Clean coastal waters: Understanding and reducing the effects of nutrient pollution. National Academy Press, Washington, D.C.

World Resources Institute. Food consumption and disruption of the nitrogen cycle.

Naylor, R. et al. 2000. Effects of aquaculture on world fish supplies. Nature 405:1017-1024.

Paez-Osuna, F. et al. 1999. Discharge of nutrients from shrimp farming to coastal waters

of the Gulf of California. Marine Pollution

Bulletin 38(7):585-592.