As stated above, through research by the Intergovernmental Panel on Climate Change (IPCC), roughly 1bn hectares of additional forest area would be needed to limit global warming to 2,0°C. 

The following maps by the World Resources Institute (Global Forest Watch) show the global forest cover, the extent of forest destruction and the afforestation potential. More than half the restoration potential lies in the six countries Russia, the US, Canada, Australia, Brazil and China.