A single hurricane hitting New England could result in the release of more than a tenth of all the carbon stored in the area鈥檚 forests, according to a modelling study. The findings show that carbon-offsetting schemes greatly underestimate the risks posed by hurricanes, says聽 at Dartmouth College in New Hampshire.
The forests of New England 鈥� which includes Connecticut, Maine, Massachusetts, New Hampshire, Rhode Island and Vermont 鈥� have been expanding for over a century, mainly due to a reduction in farming in the region. Forests now cover around 75 per cent of the land area and remove about 16 million tonnes of carbon dioxide from the atmosphere each year.
Emissions offsetting schemes are selling carbon credits to support the conservation of these forests. But the credits allow a buffer of just 3 per cent for catastrophic losses from events such as storms. 鈥淎ll it takes is one storm to completely negate that buffer pool,鈥� says Tumber-D谩vila.
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Storms are just one of many risks, he says, which also include threats such as disease and wildfires. For instance, the buffer pool allowed for wildfires in California鈥檚 carbon-offsetting programme has already been almost used up.
To work out what the impact of a major hurricane could be in the future, Tumber-D谩vila鈥檚 team looked back at the 10 biggest storms to strike New England in the 20th century. The Great New England Hurricane of 1938, for instance, downed 70 per cent of standing trees in places.
The team used several different computer models to calculate the carbon losses that would occur if the 10 storms happened again with the same wind speeds, or wind speeds 8 or 16 per cent higher 鈥� which could happen as a result of global warming.
A storm with the same wind speeds as past storms could down trees containing around 120 million tonnes of carbon, while those with winds 16 per cent stronger could release around 250 million tonnes, the team concludes.
These estimates are conservative, says Tumber-D谩vila. 鈥淭here鈥檚 a lot of factors in our analysis that lead to this being an underestimation.鈥�
For instance, the study looks only at above-ground carbon and doesn鈥檛 take into account carbon in tree roots. Nor does it account for the loss of trees or other vegetation in non-forested areas.
The release of carbon from the downed trees back into the atmosphere will be a slow process, the study also concludes. It would take 50 years for 77 per cent of the downed carbon to be emitted, and 100 years for 88 per cent to be released.
This isn鈥檛 just because it takes a long time for large trees to decompose. The study assumes that a quarter of the wood is salvaged and that some of it ends up in long-lasting products such as furniture.
鈥淭he emissions from hurricanes are really dependent on human decisions, on how much we salvage and what products that goes into,鈥� says Tumber-D谩vila.
bioRxiv
