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Deforestation Drives Changes in Climate, Food Production

Apr 02, 2015 03:53 PM EDT
Pictured: The Amazon rainforest.
(Photo : Neil Palmer/CIAT/Flickr)

Deforestation is driving changes in the climate that threaten to impact global food production, according to a new study.

"Understanding the precise mechanisms of forest-generated warming or cooling could help regional management agencies anticipate changes in crop yields. Together with a knowledge of other ecological factors, this information can help decision makers and stakeholders design policies that help to sustain local agricultural practices," co-author Safa Motesharrei said in a statement.

And with food shortages a major concern in the future as the human population grows to unsustainable levels, adding fuel to the fire in the form of deforestation is needless to say worrying to scientists.

Ironically, agriculture is widely believed to be one of the main causes of deforestation - that is, when forests are mowed down and converted to plantations for oil palm, soy, rubber, coffee, tea, rice, and many other crops. Such dramatic changes in land cover could trigger a rise or fall in local temperature by as much as a few degrees. This, in turn, could substantially impact yields of crops that are highly susceptible to specific climate conditions, resulting in harvests that are less productive and less profitable.

While local impacts of forest cover change are some of the most relevant for management practices, they're also the most poorly understood. So to better understand the effect worldwide deforestation has on local climate, researchers from the United States and China focused on the albedo and evapotranspiration effects. (Scroll to read on...)

Evapotranspiration data via MODIS/NASA.
(Photo : University of Maryland) Evapotranspiration data via MODIS/NASA.

Albedo refers to the amount of the Sun's radiation reflected from Earth's surface, whereas evapotranspiration is the transport of water into the atmosphere from soil, vegetation, and other surfaces.

The way it works is forests have a darker surface than, for example, an agricultural field. Forests therefore have a lower albedo, which means less solar radiation is reflected and more is absorbed. This phenomenon results in warming. On the other hand, forests absorb more rainwater and transpire it as water vapor later - called evapotranspiration - which causes cooling.

"These two competing biophysical effects could determine whether - at a specific location or during a specific time of the day or season of the year - a forest could cause local cooling or warming. And, by extension, whether clearing a forest could lead to a rise or fall in local temperature," explained Yan Li of Peking University, lead author of the study and visiting climate scientist at the University of Maryland.

Until now, scientists have been able to paint an accurate global picture of how forest cover impacts local climate and therefore food production. Where earlier studies relied on field observations or global climate models, this latest research used high-resolution data from NASA's Moderate Resolution Imaging Spectroradiometer, or MODIS, satellite.

"We knew before that forests have an impact on temperature. But this study has provided a precise, quantitative estimation of the impact of forests depending on the geographical location, tracing it back to the changes in albedo and evapotranspiration," said Eugenia Kalnay, a co-author of the study.

The world has already lost an estimated 130 million hectares of forest in the last decade alone, according to the Food and Agriculture Organization of the United Nations (UN). That's an area roughly twice the size of France. Though, the UN pledged back in October to halve destructive deforestation by 2020, and completely end losses by 2030.

Such drastic measures would effectively save between 4.5 billion and 8.8 billion tons of carbon emissions per year by 2030. And the sooner we work to stop deforestation worldwide, the better, because the more forests we clear, the more we increase risks for food production due to changes in temperature.

The study findings were published in the journal Nature Communications.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

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