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| LSU Professor Kam Biu-Liu spends a lot of time looking at fingerprints, but a CSI he is not. At the "scenes" he examines, no dusting is necessary and there are no yellow police tape barriers. Indeed, his investigative work has nothing to do with crime Liu is a destruction detective. By examining the "fingerprints" of past hurricanes, Liu has worked for more than a decade to decipher the past and determine what the future may hold for the Gulf Coast and coastal regions around the world. After setting the scientific world ablaze with his pioneering work in this emerging field of "paleotempestology," Liu is now studying evidence of a connection between two of the most destructive natural forces faced by people and ecosystems along the Gulf Coast: storms and fire. Liu's previous research involved examining sediment in coastal lakes and marshes along the Gulf of Mexico and Atlantic Ocean in order to reconstruct the frequency and intensity of hurricane landfalls dating back some 5,000 years. The process is relatively simple: The storm surge that accompanies a hurricane washes up onto the shoreline when a storm makes landfall. This "storm overwash" carries sand from the beach and dunes into coastal lakes and marshes, forming a sand layer. With each new hurricane comes a new layer of sand--a "fingerprint." By digging up sediment "cores" and using radio-carbon methods to date the layers, Liu has been able to determine the number of hurricanes that have hit the coast for the ast five millennia. Now, Liu, LSU's James J. Parsons Professor of Geography, is looking at these cores for layers of charcoal particles that indicate major fires in the vicinity. "When there is a fire, microscopic charcoal particles are released into the air and can disperse over a large area," explained Liu. "Some of these are deposited in lakes and become part of the sediment. If you look at the particles in the core and there is a spike (in the number of charcoal particles), it could be evidence of a large fire in the past." In recent years, some ecologists have suggested a link between hurricanes and coastal wildfires. The reasoning, Liu said, is that, during a hurricane strike, trees are brought down and vegetation is killed and this debris accumulates and dries on forest floors. Thus, there is an ample amount of "fuel" to burn, should something like a lightning strike or human error ignite it. Liu says that evidence from his examination of prehistoric sediment may back up this hypothesis. He explained that modern data is not very useful in testing the idea, because human intervention is so prevalent. For instance, fire departments have gotten better at containing blazes and lumber companies frequently haul away fallen trees. "Human intervention interferes with the data, so the best way to test is to go back to prehistoric times," he said. So far, Liu has been going back by working at a lake along the Alabama coast where he had previously gathered hurricane data. He examined a core taken from the lake that went back some 1,300 years. In the core, he found seven sand layers, indicating hurricanes, and then he conducted a charcoal and pollen analysis of the sediments. According to Liu, the work is still in the early phases and he plans on continuing it at other sites along the Gulf Coast. However, he said, the evidence thus far supports a strong connection between fires and hurricanes. "We found four very prominent charcoal layers in the core and three of them were right above sand layers," he said. "Thus, right after a hurricane strike, there was a catastrophic fire." Liu will present his findings on hurricanes and fires at the16th Congress of the International Quaternary Association, held in Reno, Nev., July 23-31. He will serve as an invited speaker in a symposium called "Environmental Catastrophes and Recovery in the Holocene." The title of his presentation will be "Holocene History of Catastrophic Hurricanes and Fires Along the U.S. Gulf Coast." In Liu's previous studies of hurricanes, he found that catastrophic hurricanes--those of categories 4 and 5--make landfall in the U.S. about once every 300 years, with the numbers higher along the Gulf Coast than the Atlantic Coast. His findings also showed that there are fluctuations in hurricane activity from one millennium to another, just as there are from one decade to another. These fluctuations are the result of varying climatic patterns that cause hurricanes to be mild and infrequent during some periods in history, and to be catastrophic during other time spans. While the 300-year time frame might be considered good news to some coastal residents, the bad news is that hurricane activity during the past millennium, when compared with other periods of time, has been mild and inactive, Liu said. "People think Camille and Andrew were devastating, but we haven't seen anything yet," Liu said. "If we switch back to a more active state, the U.S. could be hit a lot more frequently than we've seen in our lifetimes. There is a very distinct millennial-scale variability, and in the past 1,000 years, there has been a very low incidence of major hurricane landfalls along the Gulf Coast." Liu said such information is vital to coastal-development planners and insurance-risk assessors, not to mention the millions of people in America who live in coastal zones. He hopes the new data that he is collecting on the hurricane-fire connection will also be helpful to fire departments and communities. Even with human intervention, he said, fire risk can still be substantial and fire damage severe, particularly if there is a dry spell. As an example, he points to the rampant wildfires Florida faced after a drought period in 1998. If the connection between hurricanes and fires holds, it may help people to prepare for wildfire events in the future. For more information, contact Liu at 225-578-6136 or kliu1@lsu.edu. |
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