Stopping farmland expansion will help limit greenhouse emissions

Carbon sinks refer to areas that can absorb excess carbon dioxide that would otherwise accumulate in the atmosphere and further drive climate change. Forests and oceans are key examples of carbon sinks and are capable of storing vast amounts of CO2.

However, forests are being converted to farmland in many areas of the world, contributing to rising greenhouse gas levels.

Better agricultural management is key to preventing forest declines but until now, researchers were not sure which strategy would best minimize carbon loss into the atmosphere due to converted forests.

A new study conducted by researchers from the University of California-Santa Barbara and the University of Cambridge examined three land-use strategies for farmers to see which was the most effective at reducing carbon loss while still maintaining crop yields.

The results were published in the journal Current Biology.

One strategy the researchers considered was called land sparing, which involves farmers maximizing crop yields on existing farmland and leaving forests alone.

The researchers reviewed different land uses across a wide range of environments including palm oil plantations in Ghana, cattle ranches in Mexico, and arable cropping in Poland.

Field surveys of over 11,00 trees were also included in the research as well as in-depth interviews with farmers.

“At one extreme, farmers can try to produce all their food from as small an area of farmland as possible, by having very high yields,” said David Williams, the lead author of the study. “At the other extreme, farmers can try to use lower yield farming practices to increase the carbon stored on farmland, which will reduce the area of natural habitats available for conservation. And then there are all the in-between strategies that use a mix of high and low yield farmland.”

The results showed that land sparing was the best option for conserving forests, protecting natural habitats, limiting the decline of carbon sinks, and still keeping up with food demand.

“We found that the first strategy–what we call ‘land sparing’ resulted in a greater amount of carbon being stored than any other,” said Williams. “So, slightly counter-intuitively, trying to conserve carbon on farmland resulted in less carbon being stored across the landscape as a whole. This was because it resulted in lower yields and so required larger areas to produce the same amount of food, and therefore meant less land could be spared for natural habitats.”

The results were consistent across the different environments the researchers studied and land sparing has the most potential for reducing carbon loss no matter how much or little food is produced on cropland according to the researchers.

Although the results provide alternative land use strategies to reduce carbon loss, the researchers note that due to increasing food demand, large amounts of carbon will be sequestered to the atmosphere regardless of what actions are taken in the future.

Conserving natural habitats is just one part of the puzzle, and other climate change mitigation efforts will have to include decreasing food waste, limiting meat consumption due to the large carbon footprint of livestock and meat processing, and finding innovative ways to keep up food demand.

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By Kay Vandette, Earth.com Staff Writer

Image Credit: Ben Phalan