Will Amazon logging threaten US food supply?

As deforestation of the Amazon continues, the effects could be felt as far as the western United States. According to a new study, logging could trigger changes in climate that ultimately dry out important farming regions in California.

Researchers have predicted that logging in the Amazon will make the local climate warmer and drier. But what consequences will it have for other parts of the world? Scientists already know of one way that tropical climate patterns influence the weather elsewhere: El Nino events “arise from the natural variability of tropical climate,” the study authors note in the Journal of Climate, and affect other areas such as California, Oregon, and Washington.

The researchers looked at an extreme case: the effect of complete Amazon deforestation on U.S. climate. Using computer models, they predicted that precipitation along the U.S. northwest coast would drop by 10 to 20 percent, and Sierra Nevada snowpack would drop by as much as half. Agricultural areas in California, which need water for irrigation, could suffer, the team says.

“The big point is that Amazon deforestation will not only affect the Amazon — it will not be contained,” said study co-author David Medvigy of Princeton University in New Jersey in a press release. “It just so happens that one of the locations feeling that response will be one we care about most agriculturally. If you change the snowpack in the Sierra Nevada, where most of the irrigation for California’s Central Valley comes from, then by this study deforestation of the Amazon could have serious consequences for the food supply of the United States.”

Researchers will now need to run simulations to determine the effects of less extreme deforestation. For instance, parts of the Amazon are protected and less likely to be logged. Future studies also need to consider how deforestation and changes in greenhouse gas levels will interact to affect climate in the United States. Roberta Kwok | 12 November 2013

Source: Medvigy, D. et al. 2013. Simulated changes in northwest U.S. climate in response to Amazon deforestation. Journal of Climate doi: 10.1175/JCLI-D-12-00775.1.

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