Daniel J. Zarin - Where the trees are disappearing
(CNN) -- The loss of native tropical forests accounts for more than 10% of the carbon emissions responsible for the changing climate, receiving much-deserved attention at the recent U.N. climate change conference in Warsaw . When forests are cleared and burned, the carbon contained in the trees and other vegetation -- roughly half of their dry weight -- is released into the atmosphere as carbon dioxide, the main greenhouse gas contributing to global warming. Most of the carbon dioxide emissions caused by human activity come from fossil fuels. But native tropical forests average about 150 tons of carbon per hectare, and millions of hectares are cleared and burned every year. Over the past decade, governments and industry have responded to growing pressure to reverse deforestation, sometimes committing to reducing it to zero. But with few exceptions, we've lacked the tools to assess accountability. This changed when Science magazine published a groundbreaking analysis of