With 7 billion people on the planet and some 40 percent of earth’s land surface already covered with croplands and pastures, the only remaining frontiers for agricultural expansion are dwindling tropical forests. Some see high-yield industrial-scale farming as a way to take the pressure off; the theory goes that if more produce can be grown on less land, we won’t need to chop down more trees. But does it really work that way? Not necessarily, says Columbia University professor Ruth deFries, who heads an interdisciplinary research group studying land-use patterns in the Amazon regions of Brazil and Peru. She told the annual meeting of the American Association for the Advancement of Science that expanding industrial-scale farming is in fact eating forests in some areas; it works as a conservation strategy only when accompanied by incentives to use lands that have already been cleared. Her talk was part of a session on how to feed a growing population and still conserve vital planetary resources.
One group study looked at the Ucayali River region of the Peruvian Amazon, where smallholder farmers have in recent years cleared vast patchworks for traditional slash-and-burn farming. Lately, industrial-scale oil-palm plantations that produce biofuels are moving in, but instead of using already cleared areas, three quarters are pushing outward into old-growth forests. The study found that smallholders are also starting to grow oil palms; they got lower yields than the big plantations, but three quarters of them used existing cleared lands. “Just because we can produce more on less doesn’t mean people will stop expanding,” she said. She speculated that the corporate growers are using up forests simply because it is easier to assemble large holdings there than to deal with the messy ownership issues in places where people have already settled. Led by graduate student Victor Gutiérrez Velez, the study appeared recently in the journal Environmental Research Letters.
A second study looked at the Brazilian Amazon frontier state of Mato Gross, traditionally a major hot spot of deforestation; by around 2000, a full quarter of the world’s deforestation was being carried out there. Then, things reversed. From 2006 to 2010, agricultural production in the state reached an all-time high, mainly due to growth in industrial-scale soybean cultivation. Yet, during those years, deforestation plummeted to a third of its former level. The researchers showed that 90 percent of the soy expansion was on land previously cleared for pasture–not into outlying forests. “There is a lot of land in Mato Grosso left to clear, but they didn’t use it,” said de Fries. The study suggested that early on, declines in deforestation were connected to global declines in soy prices–but when prices rebounded, it was government policies against deforestation that kept back expansion into forests. Another factor was the abundance of abandoned pastures ready for conversion. The study, led by Marcia Macedo, was published recently in the Proceedings of the National Academy of Science.
The respite may not last, said de Fries; under pressure from big agriculture, Brazil is considering loosening restrictions on deforestation. Another speaker, Jonathan Foley of the University of Minnesota’s Institute on the Environment, pointed out that much of the pressure is due not just to sheer population growth, but to per capita increases in consumption of meat, biofuels and timber. Rising living standards mean that agricultural production will have to double by 2050 he said, even if the population does not. “Figuring out how we can achieve food security and sustainability, and in the future have 9 billion people who can have a decent life is the defining challenge of our time,” he said.