Sustainability Science

The new study, led by the U.N. Food and Agriculture Organization and published in Global Change Biology, quantifies the reductions in climate pollution from the degradation and clearcutting of forests. Clearcutting most often clears space for agriculture, suggesting agriculture’s indirect climate impacts surpass the impacts of deforestation for timber and other commodities. The researchers aim to tally those indirect impacts later this year. This paper was an early step in a larger effort to better understand and report on the climate repercussions of how land is used. “Every year, we’ll have updates,” lead author Francesco Tubiello said.

The study is also a reminder that the burning of fossil fuels remains the main cause of global warming. Burning fuel produces about four times more climate pollution every year than forestry and agriculture combined — a figure that is growing. The research shows that the recent climate-protecting gains in forests are being nearly canceled out by efforts to satisfy the world’s growing appetite — particularly its appetite for meat. Greenhouse gases released by farming, such as methane from livestock and rice paddies, and nitrous oxides from fertilizers and other soil treatments rose 13 percent after 1990, the study concluded. Agricultural climate pollution is mostly caused by livestock. Cows and buffalo are the worst offenders — their ruminating guts and decomposing waste produce a lot of methane. They produce so much methane, and eat so much fertilized feed, that livestock are blamed for two-thirds of agriculture’s climate pollution every year. “We’re seeing an expansion of agricultural lands in some areas because of the growing global population,” Jackson, who is a co-chair of the Global Carbon Project, which studies the global carbon cycle, said. “We’re also seeing intensification of agriculture.”

Although annual climate pollution from deforestation is declining, experts warn that recent gains could quickly be reversed.Deforestation in the Amazon rainforest spiked recently following nearly a decade of declines, for example, as farmers and loggers rushed to exploit loopholes in forest protection laws. Some parts of Central Africa are seeing deforestation in areas where it was not previously a problem. And cutting down trees can reduce moisture levels in a rainforest, which could cause parts of the Amazon to start dying off — even if everybody’s chainsaws simultaneously jammed. The researchers drew on three global datasets to try to hone in on land’s changing contribution to global warming. Such impacts are harder to quantify accurately than are the pollution impacts of burning fuel. Governments invest fewer resources tracking and reporting complex climate indicators for deforestation and agricultural activity than is the case for the energy sector. The paper noted a gulf between global efforts to reduce the climate impacts of deforestation, and the dearth of a global response to the climate impacts of food production. REDD is a major focus of U.N. climate negotiations, but agriculture is barely discussed during the talks….

...Doug Boucher, the director of climate research at the Union of Concerned Scientists, says agriculture’s climate impacts could be reduced without taking food off tables. Reducing the overuse of fertilizers, protecting the organic content of soils by changing farming practices, and keeping rice paddies flooded for fewer weeks every season could all contribute to a climate solution, he said.The biggest opportunities for reforming agriculture’s climate impacts can sometimes be found miles from where any food is grown. Reducing waste where food is sold, prepared, eaten and, in many cases, partly tossed in the trash as uneaten leftovers or unsellable produce, reduces the amount of land, fertilizer and equipment needed to feed everybody. “Shifting consumption toward less beef and more chicken, and reducing waste of meat in particular, are what seem to have the biggest potential,” Boucher said.