Converting Forests to Cropland Actually Cooled the Planet

Researchers have recently discovered that over the last 150 years, the conversion of forests into cropland has actually resulted in a small amount of global cooling. These results underscore the overall complexity of the climate change issue.

According to a study recently published in the journal Nature Climate Change, large-scale forest losses that have occurred over the last 150 years have actually reduced global emissions of biogenic volatile organic compounds (BVOCs) - agents that aid the distribution of many common pollutants, including methane and even tropospheric ozone.

BVOC is a little-considered type of emission that, oddly enough, most crops do not release into the atmosphere - but trees do.

Using a sophisticated modeling system, study author Nadine Unger of the Yale School of Forestry & Environmental Studies (F&ES) calculated that thanks to forest decline between 1850 and 2000, there was a 30 percent drop in BVOC emissions, causing a net cooling of about 0.1 degrees Celsius around the world.

"Land cover changes caused by humans since the industrial and agricultural revolutions have removed natural forests and grasslands and replaced them with croplands," Unger explained in a statement. "And croplands are not strong emitters of these BVOCs - often they don't emit any BVOCs."

However, climate change deniers shouldn't break out the party hats just yet. Over the same time period, the global climate warmed by about 0.6 degrees Celsius (about 1 additional degrees Fahrenheit) thanks to the effects of carbon emissions from fossil fuel burning.

The researchers adds that while deforestation is wholly bad for the Earth, fewer dark forests can also help cool the planet thanks to something called the albedo effect. This refers to the amount of sunlight reflected by the surface of the planet, in which light-colored fields reflect more light and heat back into space than darker forests.

However, in the same breath, she adds that this albedo cooling certainly does not counteract the long-term adverse effects fewer trees will have on the planet - namely fewer trees to use and store harmful carbon dioxide.