Tropical Cyclones Play Major Role in Increased Carbon Uptake by Southeast U.S. Forests

For people who reside in the southeastern United States, hurricanes continue to be a major source of worry, but according to a new study, residents of this region may now have a major upside on how to offset global warming. Earlier, Duke environmental engineer Ana Barros performed a study, which showed that a steady landfall of tropical cyclones is important for the region’s water supply and this can ultimately help in reducing droughts.

This map shows the total increase of photosynthesis and carbon uptake by forests caused by all hurricanes in 2004. The dotted gray lines represent the paths of the individual storms. (credit: Lauren Lowman, Duke University)

Barros carried out a new study, which showed that the landfall of tropical cyclones in the southeastern has contributed to an increased level of forest photosynthesis and growth, which captures significant amounts of carbon that is much more than the amount of carbon released by all US vehicles in a given year. The results of the study have been published online in the Journal of Geophysical Research - Biogeosciences.

Our results show that, while hurricanes can cause flooding and destroy city infrastructure, there are two sides to the story. The other side is that hurricanes recharge the aquifers and have an enormous impact on photosynthesis and taking up carbon from the atmosphere.

Ana Barros, the James L. Meriam Professor of Civil and Environmental Engineering, Duke University

In order to replicate the ecological effects of tropical cyclones between the period of 2004 and 2007, Lauren Lowman, a doctoral student in Barros’s laboratory, applied a hydrological computer model. A high number of tropical cyclone landfall events were experienced in the earlier years of that period, while there were relatively few events in the latter years. Lowman compared those different years to simulations of a year sans the tropical cyclone events, and then determined the impact of tropical cyclones on the rates of photosynthesis and the uptake of carbon in the southeast U.S. forests.

It’s easy to make general statements about how much of an impact something like additional rainfall can have on the environment. But we really wanted to quantify the amount of carbon uptake that you can relate to tropical cyclones.

Lauren Lowman, Doctoral Student, Duke University

According to Lowman and Barros, it is not easy to estimate the extent of effect climate change will have on the region in the coming days. Even if there are a high number of tropical cyclone events in the Atlantic region, there is no assurance that the number of landfall events will also increase simultaneously. At present, long-term forecasts for temperature and rainfall in the region do not show any major change than the usual year-to-year changeability. Regardless of future scenarios, the fact remains that the number and regularity of tropical cyclone landfall events will continue to be of major significance.

There are a lot of regional effects competing with large worldwide changes that make it very hard to predict what climate change will bring to the southeastern United States. If droughts do become worse and we don’t have these regular tropical cyclones, the impact will be very negative. And regardless of climate change, our results are yet one more very good reason to protect these vast forests.

Ana Barros, the James L. Meriam Professor of Civil and Environmental Engineering, Duke University

The study was partly supported by the National Science Foundation Coupled Human and Natural Systems Program (CNH-1313799), and an earlier grant from the National Oceanic and Atmospheric Administration (NA08OAR4310701).

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