By STEPHEN PORDER - November 24, 2013
A FEW years ago, one of my graduate students showed me a Google Earth image that changed my view of the world. On a photo showing all of South America, I could clearly see a single soybean farm in the Brazilian state of Mato Grosso. My first thought was that a farm that big, sitting on the edge of the Amazon, must be an environmental disaster. But when it comes to agricultural sustainability, all is not what it seems.
Despite what you might hear at your local farmers’ market or Whole Foods, not all big farms are bad. Nor are all small organic farms sustainable. They may produce high-quality food, but if they don’t produce a lot of calories per acre, they are doing little to help increase the global food supply. How we increase this supply over the next few decades will determine agriculture’s sustainability. It’s worth exploring why this is so, because sustainable food production is a fundamental human need. Getting it right will require us to carefully assess the consequences of where and how we farm.
Already, the world’s farms take up an area the size of South America. By 2050, a global population of nearly 10 billion people will require roughly 70 percent more food. We have two options: Either we need to get more food out of the land we already farm, or we need to farm more land.
Nowhere are farmers pursuing the first option faster than in Mato Grosso. Last January I decided to see the consequences for myself. After a long flight from Boston, I rode the night bus nearly 500 miles of rutted roads to reach the frontier town of Canarana. Only about 25,000 people live here, but the main street has several stores selling million-dollar tractors. Waiting for my ride to the farm, I met a man from Silicon Valley who commutes every month to sell heavy equipment. He told me, “This is where the money is.”
How can we determine if these farms are sustainable? Admittedly, it’s unnerving to stand in an endless sea of soybeans where there was once rain forest. Exotic animals like tapirs, jaguars and rheas wander through the monocrop desert, and macaws compete for airspace with crop dusters. But sustainability has little to do with appearances. Sustainability depends on whether a farm can continue to produce food over the long term, without irreparably damaging the environment or causing other land to be cleared in the quest for increased food production.
For the past five years, my students, colleagues and I have been trying to understand the sustainability of these giant soy farms. Although I typically work on tropical forests and the soils that sustain them, the fate of the forests I love is intimately intertwined with the way people use them. When colleagues suggested that I come to Mato Grosso to see this bustling agricultural frontier, I jumped at the chance.
We focused first on fertilizer. Fertilizer helps grow more food on a given plot of land, but overuse can have serious environmental consequences. Largely, these depend on how efficiently farms use nitrogen and phosphorus. These two elements, which limit how much crops can grow, are the main components of fertilizer. Crops don’t absorb all the fertilizer farmers apply, and what’s left behind often ends up in waterways, where it fuels algae growth. Fifty years of heavy fertilizer use in the breadbaskets of the United States and Europe has left lakes, rivers and coasts with algae-choked “dead zones.”
We expected the story to be similar in Mato Grosso. But to our surprise, we’ve found that streams draining the farms there have no more nitrogen or phosphorus than those in adjacent forests. The deep tropical soils are highly efficient filters, removing nutrients before they reach the water. In the American Midwest, scientists have long been searching for ways to clean up farm runoff. In Mato Grosso, the soils do the work.
But these same soils present a sustainability concern on a different front. After millions of years of heavy rainfall, Mato Grosso’s soils have lost nearly all their phosphorus. The soils efficiently remove phosphorus before it reaches the streams but also bind phosphorus added as fertilizer, leaving less for the crops. As a result, farms here require twice as much phosphorus fertilizer as their counterparts in more temperate regions, where the soils are younger and more fertile. And phosphate ore, the source of phosphorus fertilizer, is a finite resource.
The world’s phosphorus reserves are held by a handful of countries — the exact distribution is disputed, but possibly half of it is in Morocco alone. Much of Morocco’s phosphate ore is carried 61 miles across the Western Sahara to the Atlantic, on the world’s longest conveyor belt. A farm might not be sustainable if it depended on political stability in faraway countries. And how should we weigh the negative of phosphorus depletion against the positive of reduced water pollution? We don’t yet know the answers.
The fertilizer story makes it complicated to figure out the sustainability of Mato Grosso’s farms, which send their soy to China, as animal feed, and to Europe. Even more complicated is the question of how these farms will affect the global climate. The link, while not obvious, is important. Global warming results largely from burning fossil fuels. But another important contributor — about 15 percent of our carbon-dioxide emissions — comes from changing land use, primarily the burning of tropical rain forests to make room for food or biofuel crops. If we really want to know the environmental impact of these soy farms, we need to understand their effect on carbon-dioxide emissions.
Natural science alone cannot answer this question, so I increasingly find myself talking to economists and sociologists. Because at the end of the day, the carbon footprint of these farms will depend on whether their economic success leads to more deforestation. If so, their carbon footprint will be huge. This would be a deathblow to their sustainability.
On the other hand, these soy fields produce more calories than the low-productivity pastures they replaced. Remember options one and two: To feed a growing population we will need to either farm more land, or to get more food out of the land we farm. Either option will need to be coupled with efforts to reduce food waste and to feed fewer crops to animals.
For now, deforestation rates in Mato Grosso have slowed, as pastures have been converted to soy. It may be that megafarms, unlike the small-scale landholders they replace, are more reticent to take on the sanctions that come with illegal deforestation, though there are certainly other potential explanations. We don’t know if the slowdown in deforestation will continue. If it does, and if big soy is a reason, one could argue that these fields are a boon to the global environment far greater than your local organic farm.
One thing is clear: In the coming decades we will need to produce a lot more food. I’m not suggesting Mato Grosso’s farms are the answer, far from it. But it’s time to move beyond the oversimplification that large-scale agriculture is incompatible with environmental goals. There are vast areas of the tropics with similar soils. They are likely to be the megafarms of the future.
We need to admit that food production is going to be the dominant use of land in the 21st century, and to decide whether we are going to farm more land or farm more intensively. Then we can move on to the grand challenge of making our farms sustainable.