For a while after scientists (and Al Gore!) first started talking about global warming, it seemed like biofuels might be the magic solution to our energy needs.
Made from corn, sugarcane, palm oil, soybeans and various other organic matter, biofuels burn "clean," which means that they don't contribute to climate change nearly as much as fossil fuels like coal. And farmers can grow a new crop every year, meaning the supply is almost limitless.
(Fossil fuels power industrial production, transportation, electricity, sewage treatment...basically, everything. But when burned, fossil fuels release tons—literally, tons—of carbon dioxide into the atmosphere. This excess carbon dioxide traps heat. The research is still ongoing, but scientists say the consequences of a warmer planet may include melting ice caps and more "extreme weather events" like tornadoes and hurricanes.)
But researchers at the Smithsonian Tropical Research Institute warn that these fuels, too, should be approached with caution.
The STRI scientists suspect that farmers in the tropics—which is where most biofuel crops are grown—are chopping down rainforests to make space for crops like sugarcane and soy. What's wrong with that?
Trees, particularly those in the rainforest, store carbon dioxide and keep it out of the atmosphere. But when a tree is cut down, it releases its store of carbon dioxide into the air.
So if farmers are cutting down rainforests to produce biofuel—and researchers believe that this is what's happening—then their attempts to reduce carbon dioxide emissions might actually increase carbon dioxide emissions.
Talk about a vicious cycle.
"We're between a rock and a hard place," says William Laurance, one of the STRI researchers who warned against deforestation. "We need to conserve, conserve, conserve."
That means we're back at the beginning: less use of all fuels, bio and fossil alike.