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Untangling the confusion around land carbon science and climate change mitigation policy

2013; Nature Portfolio; Volume: 3; Issue: 6 Linguagem: Inglês

10.1038/nclimate1804

1758-6798

Brendan Mackey, I. Colin Prentice, Will Steffen, Joanna I. House, David B. Lindenmayer, Heather Keith, Sandra L. Berry,

Global Energy and Sustainability Research

Two important aims of mitigation policy are to maintain land carbon stocks and reduce terrestrial ecosystem-based emissions. This Perspective discusses the scientific issues involved, argues that current negotiations under the United Nations Framework Convention on Climate Change are not solidly grounded in science, and proposes some ways forward. Depletion of ecosystem carbon stocks is a significant source of atmospheric CO2 and reducing land-based emissions and maintaining land carbon stocks contributes to climate change mitigation. We summarize current understanding about human perturbation of the global carbon cycle, examine three scientific issues and consider implications for the interpretation of international climate change policy decisions, concluding that considering carbon storage on land as a means to 'offset' CO2 emissions from burning fossil fuels (an idea with wide currency) is scientifically flawed. The capacity of terrestrial ecosystems to store carbon is finite and the current sequestration potential primarily reflects depletion due to past land use. Avoiding emissions from land carbon stocks and refilling depleted stocks reduces atmospheric CO2 concentration, but the maximum amount of this reduction is equivalent to only a small fraction of potential fossil fuel emissions.