Bob Holmes, New Scientist 27 Apr 09;
Destruction wreaked by hurricanes over the past 150 years has severely affected the ability of US forests to store carbon, say ecologists.
The finding suggests that an increase in hurricanes and tropical storms induced by global warming could turn forests into overall emitters of carbon dioxide, fuelling further climate change.
Trees absorb CO2 from the atmosphere as they grow, then release it again when they die and decay. Ecologist Jeffrey Chambers of Tulane University in New Orleans, Louisiana, and his colleagues used data on hurricanes and the damage they have caused to estimate the total loss of biomass in US forests for every year from 1851 to 2000.
They calculated that storm damage released an average of 25 megatonnes of CO2 into the atmosphere each year. More detailed measurements for the 1980s suggest that because of this damage, US forests absorbed up to 18 per cent less CO2 than they otherwise would have – even though the decade experienced below-average hurricane damage.
At present, worldwide forest growth offsets about 25 per cent of CO2 emissions from fossil fuels, says Chambers. But if, as many climate scientists predict, hurricanes become more common or more severe, the added forest damage that will occur in the US and elsewhere could reduce that offset substantially.
Journal reference: Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0808914106
