Forests are an indispensable piece of the climate puzzle, which is why they’re prominent in the U.N.’s new Sustainable Development Goals, and why they will also loom large at the COP21 Paris climate talks. The land sector — agriculture, forestry and other land use — is the second-largest emitter of greenhouse gases after energy. It accounts for almost a quarter of global emissions, including about 10 to 11 percent from deforestation, and the rest from…