As mentioned earlier, deforestation creates a lot of greenhouse-gas emissions—accounting for more than one-quarter of humanity’s total annual output of carbon-dioxide. Because these emissions are so large, negotiators at the U.N. climate talks in Bonn are currently trying to figure out how to include forestry in whatever international carbon-trading scheme succeeds the Kyoto Protocol. Yet a new policy brief from The Nature Conservancy explains that if this carbon-credit scheme only focuses on outright deforestation, it's going to be unsuccessful. That's because there are more ways to cause a forest to belch carbon than clear-cutting.

Consider, for instance, selective logging, in which only some of a forest's trees—usually the most valuable ones—are cut down. Then there's the collection of wood for fuel or forest fires. Those don't count as "deforestation," but they can release a significant amount of carbon. Fires, in particular, are significant—during especially dry El Ni