科技英语新闻:Sugarcane can cool climate, study finds

LOS ANGELES, April 18 (Xinhua) -- Sugarcane has the effect of cooling temperatures, thus playing role in stemming global warming, a new study has found.

Sugarcane does so by reflecting sunlight back into space and by lowering the temperature of the surrounding air as the plants " exhale" cooler water, according to the study conducted by researchers at the Carnegie Institution's Department of Global Ecology.

The researchers used data from hundreds of satellite images over 733,000 square miles (about 1,173 square kilometers) in Brazil, where sugarcane is widely grown. They measured temperature, reflectivity (also called albedo), and evapotranspiration -- the water loss from the soil and from plants as they exhale water vapor.

The findings showed that expansion of sugarcane in areas previously occupied by other Brazilian crops cools the local climate.

Converting from natural vegetation to crop/pasture on average warmed the cerrado by 2.79 Fahrenheit (1.55 Centigrade, but that subsequent conversion to sugarcane, on average, cooled the surrounding air by 1.67 Fahrenheit (0.93 Centigrade), the researchers said in the study published in the April issue of Nature Climate Change.

"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," said lead researcher Scott Loarie. "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."

Brazilians are world leaders in using biofuels for gasoline. About a quarter of their automobile fuel consumption comes from sugarcane, which significantly reduces carbon dioxide emissions that otherwise would be emitted from using gasoline.

The researchers emphasized that the beneficial effects are contingent on the fact sugarcane is grown on areas previously occupied by crops or pastureland, and not in areas converted from natural vegetation. It is also important that other crops and pastureland do not move to natural vegetation areas, which would contribute to deforestation.

So far most of the thinking about ecosystem effects on climate considers only impacts from greenhouse gas emissions. But according to 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 core elements of human-caused climate change."