Through photosynthesis, green plants remove carbon dioxide from the atmosphere. Mindful of rising levels of atmospheric carbon dioxide and global warming, the Kyoto Protocol proposed that, if nations increase their forested areas, they should be granted emissions credits to count in their CO₂ emission standards (their permissible, and legally binding, pollution maxima); see Depledge and Lamb (2005) UNFCCC. A further proposal, emissions trading, would allow a nation with greenhouse gas emissions below its agreed target to trade its ‘credit’ to over-target nations. The impact of emissions trading will depend on the structure of the system (Voon (2000) J. Int. Law & Policy 10, 1).