The large-scale expansion of agriculture in the Amazon through deforestation will be a no-win scenario, according to a new study. Published May 10, in IOP Publishing's journal Environmental Research Letters, it shows that deforestation will not only reduce the capacity of the Amazon's natural carbon sink, but will also inflict climate feedbacks that will decrease the productivity of pasture and soybeans.

The researchers used model simulations to assess how the agricultural yield of the Amazon would be affected under two different land-use scenarios: a business-as-usual scenario where recent deforestation trends continue and new protected areas are not created; and a governance scenario which assumes Brazilian environmental legislation is implemented.

They predict that by 2050, a decrease in precipitation caused by deforestation in the Amazon will reduce pasture productivity by 30 percent in the governance scenario and by 34 percent in the business-as-usual scenario.

Furthermore, increasing temperatures could cause a reduction in soybean yield by 24 percent in a governance scenario and by 28 percent under a business-as-usual scenario.

Through a combination of the forest biomass removal itself, and the resulting climate change, which feeds back on the ecosystem productivity, the researchers calculate that biomass on the ground could decline by up to 65 percent for the period 2041-2060

Brazil faces a huge challenge as pressure mounts to convert forestlands to croplands and cattle pasturelands in the Amazon. A fine balance must be struck, however, as the natural ecosystems sustain food production, maintain water and forest resources, regulate climate and air quality, and ameliorate infectious diseases.

Lead author of the study, Dr Leydimere Oliveira, said: "We were initially interested in quantifying the environmental services provided by the Amazon and their replacement by agricultural output.

"We expected to see some kind of compensation or off put, but it was a surprise to us that high levels of deforestation could be a no-win scenario - the loss of environmental services provided by the deforestation may not be offset by an increase in agriculture production."

The researchers, from the Federal University of Vicosa, Federal University of Pampa, Federal University of Minas Gerais and the Woods Hole Research Center, show that the effects of deforestation will be felt most in the eastern Para and northern Maranhao regions.

Here the local precipitation appears to depend strongly on forests, and changes in land cover would drastically affect the local climate, possibly to a point where agriculture becomes unviable.

"These simulations strongly suggest that the act of deforestation, which is being done to increase agricultural production, may perversely lead to changes in climate that reduce crop and pasture yields" noted Dr.

Michael T. Coe, senior scientist at the Woods Hole Research Center and co-author of the study. "In some cases these decreases in yield may be large enough to make agriculture economically unattractive."

The paper can be downloaded here