Robert Jackson and colleagues at Duke University in Washington State (US) calculated that, if Nature were not compensating by absorbing carbon dioxide, the current atmospheric concentrations of carbon dioxide would be rising at twice the speed. They are worried that this 'free ride' will fade away as both factory farming and atmospheric carbon dioxide levels reduce the nitrogen content of soil, and therefore the availability of nitrogen to plants. Lower nitrogen levels in plants reduce their ability to absorb carbon dioxide.

This makes it all the more important that nations worldwide adopt the spirit and targets of the Kyoto Treaty.