Peat bogs (wetlands containing large amounts of carbon in the form of decaying vegetation) make up only about 3 percent of global land area, but their deep layers of peat contain roughly twice as much carbon as the world’s forests. When a bog is dried out, for agriculture, etc, the carbon is released to the atmosphere as carbon dioxide and other greenhouse gases. In order to make global land use a net carbon sink, it will be necessary to protect pristine wetlands and rewet about 60% of the degraded ones.