18 April 2011

Win-win for sugarcane biofuel crops

by Kate Melville

Agricultural cropping typically has a significant warming effect on local climates, but a report in Nature Climate Change indicates that Brazilian sugarcane biofuel crops cool the local climate at around the same levels as natural vegetation.

Scientists from the Carnegie Institution's Department of Global Ecology said the double ecological benefit came about from sugarcane's ability to reflect sunlight and also the high levels of water "exhaled" by the plants.

The new study is the first to quantify the direct effects on the climate from sugarcane crop expansion in areas of existing crop and pastureland in central Brazil.

"We found that shifting from natural vegetation to crops or pasture results in local warming because the plants give off less beneficial water. But the bamboo-like sugarcane is more reflective and gives off more water - much like the natural vegetation. It's a potential win-win for the climate - using sugarcane to power vehicles reduces carbon emissions, while growing it lowers the local air temperature," explained lead researcher Scott Loarie.

He added that on average, crop or pasture warmed the local climate by 2.79 & #176;F, but that subsequent conversion to sugarcane, on average, cooled the surrounding air by 1.67 & #176;F.

Loarie stressed that the beneficial effects are contingent on the fact sugarcane is grown in areas previously occupied by crops or pastureland, and not in areas converted by deforestation.

The researchers say it's time that climatologists paid more heed to local climate effects. "So far most of the thinking about ecosystem effects on climate considers only impacts from greenhouse gas emissions," said co-researcher Greg Asner. "It's becoming increasingly clear that direct climate effects on local climate from land-use decisions constitute significant impacts that need to be considered."

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Source: Carnegie Institution