Very large cuts in emissions of greenhouse gases are needed if we are to avoid the worst effects of global climate change. This report describes the vital contribution that ecosystems can and must make to these efforts. It is essential that climate mitigation policy is guided by the best available science concerning ecosystem carbon, and decisions should be informed by the overall costs and benefits of carbon management. Developing policies to achieve these ends is a challenge: it will be necessary to ensure that local and indigenous peoples are not disadvantaged and to consider the potential for achieving co-benefits for biodiversity and ecosystem services. Drylands, in particular, offer opportunities for combining carbon management and land restoration. The world’s terrestrial ecosystems are a vast store of carbon containing
more than 2000 Gt C and are acting as a net sink of approximately 1.5 Gt C per year, of which tropical forests account for a large proportion (Luyssaert et al. 2007; IPCC 2007b). Sequestration at these levels would be equivalent to a 40–70 ppm reduction of CO2e in the atmosphere from anthropogenic emissions by 2100 (Canadell and Raupach 2008).