Investigating the Carbon Impact of Hurricane Damage

NASA satellite image shows damaged and destroyed forest trees (in red) in the aftermath of Hurricane Katrina

There is a source of increased carbon emissions that not many people are looking at; the destruction of trees during a hurricane or other strong storm. Investigating situations such as this are leading scientists to better understand the carbon cycle.

Studies led by Jeffrey Chambers, who is now with the Lawrence Berkeley National Laboratory (Berkeley Lab) have found that Hurricane Katrina downed 320 million trees as it pounded the Gulf coast and inundated New Orleans. This massive loss of trees amounted to an equivalent 10-percent increase in the US fossil fuel emissions for a whole year.

“Hurricanes and other extreme events that disturb forest ecosystems have the potential to alter forest structure and and ecosystem functions, including biomass accumulation rates and forest tree species composition,” says Chambers, a researcher in the Climate Sciences Department of Berkeley Lab’s Earth Sciences Division. “Quantifying these forest disturbances is necessary to evaluate the extent and severity of damage for estimating biomass loss, developing regional carbon budgets, and making management decisions.”

Chambers and colleagues are in the process of continually developing their models that will help them to evaluate tree mortality on the carbon cycle, evaluations which will eventually be incorporated into new and improved Earth System Models, giving a clearer picture of the changing global climate.

“Whereas other research efforts focus on the size of the area impacted by a storm, we use a combination of field plots, remote sensing image analysis, and modeling techniques to estimate the number of trees that were destroyed,” Chambers says. “This is an important advancement in the assessment of large-scale disturbances to forest ecosystems.”

It is not news that trees and other green plants are critical to the carbon cycle. The focus of this new research is to be able to better monitor whether the amount of carbon being stored is greater than the amount being released through plant decomposition.

“When a forest disturbance increases the amount of decomposing dead plant material, the ecosystem can change from a sink to a source of carbon,” Chambers says. “Processes that elevate the mortality of vegetation, especially trees, can cause a weakening of the terrestrial carbon sink that contributes to climate system warming. In addition, a warming climate increases the likelihood of extreme events that cause tree and vegetation mortality, resulting in an increase in decomposing biomass. This increase in tree and vegetation mortality could act as a positive feedback mechanism that accelerates the global warming effect.”

Chambers and his colleagues have already made good use of their research, using it to gauge the impact of the hurricanes Katrina and Rita in 2005, and Gustav in 2008, all hitting the Gulf Coast region. Not only were a large number of trees destroyed, but this has left an opening for the Chinese tallow tree to invade.

“In terms of biomass and carbon, it will take probably on the order of 75 to 100 years for the forests in the region to fully accumulate the carbon lost from the decomposition of all the dead trees,” Chambers says. “However, with the invasion by the Chinese tallow and other factors, the forests there will probably never be quite the same.”

Source: Lawrence Berkeley National Laboratory (Berkeley Lab)
Image Source: NASA

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