Environmentalists have spent decades working to protect tropical forests, both to promote biodiversity and to conserve nature's bounty. All too often those efforts have fallen short in the face of economic forces that put a higher price on timber and cleared land than on the forests themselves. But that may soon change if international climate negotiators can include forest carbon in a treaty to control global warming. The path forward will not be easy, as the News Feature on Madagascar's forests on page 26 points out, but it is surely a worthy experiment.

Governments must find ways to address the social and economic problems that push people to cut down their forests.

Forest carbon represents a new way of thinking about conservation, one that measures forests in terms of the carbon they sequester in their biomass and soil. The numbers are substantial: deforestation is currently responsible for up to 20% of global carbon emissions, which means that protecting forests could noticeably slow global warming. Doing so will be difficult, though, given the social issues at play and the weak governance in many tropical nations. But it should be relatively cheap compared with other methods of reducing carbon emissions. And with carbon footing the bill, tropical forests might finally get the kind of attention — and resources — they deserve.

As the world prepares for the United Nations climate summit in Copenhagen this December, negotiations over how a new climate treaty would incorporate a market for forest conservation credits — a trading system known as 'reducing emissions from deforestation and forest degradation' (REDD) — have been among the most fruitful to date. REDD negotiators might well be closer to a deal than any of their treaty counterparts working on emissions targets, financing and the like. Developed countries see REDD as a potentially cheap and beneficial way to reduce emissions, and developing countries see it as a cash infusion that could be used to promote a new model of sustainable development.

At present, REDD pilot projects are sprouting up in communities around the tropics, often using government funds or in some cases carbon credits that have been issued on voluntary carbon markets. As helpful as these individual projects might be for improving people's livelihoods and preserving local biodiversity, however, it's not clear that they measurably reduce global-warming emissions. To realize the full promise of REDD — and to tap into the much larger flows of private money expected in future carbon markets — nations must ultimately manage their forests on a national scale. This means that they will need to beef up their science and regulatory infrastructure in order to inventory all their forest carbon, show that they can control land use at the local level and prove that their emissions are declining. Exactly how they achieve this will probably vary by country, and that is fine. As long as forests are left standing and emissions are going down, nations should have some flexibility to set up systems that most benefit their own people.

Many pitfalls lie ahead. As the situation in Madagascar shows, political instability can derail environmental reforms; continuing poverty and bad policy, as well as droughts and fires, could do the same. But governments, climate negotiators and environmentalists are working on solutions to these challenges, and there is no evidence yet that they cannot be overcome.

One thing is clear: it is at the local level that forest protection will either succeed or fail. Governments must find ways to address the social and economic problems that push people to cut down their forests, as well as instituting laws against doing so. And although it would be foolhardy to think of REDD as a panacea, the idea certainly dovetails nicely with development goals. Indeed, those nations that are able to spread the wealth in such a way that local communities see benefits are the most likely to succeed.