Background
The authors write that "expansion of global demand for soy products and biofuel poses threats to food security and the environment," noting that "one environmental impact that has raised serious concerns is loss of Amazonian forest through indirect land use change (ILUC), whereby "agricultural activities displaced from one region are reconstituted in another one (Scearchinger et al., 2008; Lapola et al., 2010)," which phenomenon, in their words, "has been hypothesized by many researchers," although they state that "it has not yet been measured statistically, owing to conceptual difficulties in linking distal land cover drivers to the point of impact."

What was done
Arima et al. overcome this previous impasse, as they describe it, "with a spatial regression model capable of linking the expansion of mechanized agriculture in settled agricultural areas to pasture conversion on distant, forest frontiers."

What was learned
In applying their model to the period 2003-2008, the four scientists determined that ILUC "is significant and of considerable magnitude." More specifically, they report that "a 10% reduction of soy in old pasture areas would have decreased deforestation by as much as 40% in heavily forested counties of the Brazilian Amazon."

What it means
Arima et al. conclude that "the voluntary moratorium on primary forest conversions by Brazilian soy farmers has failed to stop the deforestation effects of expanding soy production." And they therefore contend that environmental policy in Brazil must pay attention to ILUC, although they say that doing so can complicate that nation's efforts to achieve the goals of its United Nations-sponsored program for Reducing Emissions from Deforestation and Forest Degradation, which they say had "raised hopes for a new era of sustainable relations between coupled natural human systems in Amazonia," as discussed by Nepstad et al. (2009).

So what's new? Apparently, it's still true that The best-laid schemes o' mice an' men Gang aft agley.

References
Lapola, D.M., Schaldach, R., Alcamo, J., Bondeau, A., Koch, J., Koelking, C. and Priess, J.A. 2010. Indirect land-use changes can overcome carbon savings from biofuels in Brazil. Proceedings of the National Academy of Sciences USA 107: 3388-3393.

Nepstad, D., Soares-Filho, B.S., Merry, F., Lima, A., Moutinho, P., Carter, J., Bowman, M., Cattaneo, A., Rodrigues, H., Schwartzman, S., McGrath, D.G., Stickler, C.M., Lubowski, R., Piris-Cabezas, P., Rivero, S., Alencar, A., Almeida, O. and Stella, O. 2009. The end of deforestation in the Brazilian Amazon. Science 326: 1350-1351.

Searchinger, T., Heimlich, R., Houghten, R.A., Dong, F, Elobeid, A., Fabiosa, J., Tokgoz, S., Hayes, D. and Tun-Hsiang, Y. 2008. Use of US croplands for biofuels increases greenhouses gases through emissions from land-use change. Science 319: 1238-1240.