The twenty-first century will be decisive for both the earth’s climate and its biodiversity. One important part of the effort to reduce global warming pollution is forest preservation and restoration, particularly in the tropics where almost all of the deforestation currently takes place. The first stage, already well underway, is to reduce emissions from deforestation and forest degradation, and 2010 FAO data indicate that countries such as Brazil already have achieved major successes in this effort. But in the middle and later decades of the twenty-first century, it will be important to go further, restoring the planet’s forests to remove greenhouse gases from the atmosphere. The IPCC’s Fourth Assessment Report (2007) and more recent studies by the Union of Concerned Scientists, Resources for the Future, McKinsey and Company and the World Resources Institute provided data to assess the climate mitigation potential of forest restoration worldwide.

Results/Conclusions

Although methods and assumptions vary among the studies, the data show very considerable potential for carbon sequestration from forest restoration. Several hundred million hectares of deforested and degraded land, mostly in the tropics, could be restored to forest, providing 2-4 GtCO₂eq of additional annual sequestration by 2040 and higher rates thereafter. The possible contribution of forest restoration is considerably less than that of reducing emissions from deforestation (REDD) in the first few decades -- half or less in terms of mitigation potential. However it can become the principal land-use-based mitigation method in the later years of the 21^st century.  This effort, which will reverse humanity’s entire history of destroying forests, will benefit our descendants and the species with which we share the planet for many centuries to come.