USGS National Wetlands Research Center: Hurricane Reseach

Hurricane Research at National Wetlands Research Center

By Kyle Donaldson, Johnson Controls World Services Inc. at USGS NWRC

Studying hurricanes - from tracking the recovery process across decades past to predicting their future impact on habitats - is critical to the USGS National Wetlands Research Center's research mission. Although headquartered in Lafayette, Louisiana, NWRC's hurricane researchers find themselves at work throughout the world. Presented here are some examples of NWRC's wide-ranging hurricane research efforts.

Peering into the Past
One technique that NWRC ecologist Tom Doyle uses to peek into hurricanes past is dendroecology, the study and interpretation of tree rings. Hurricanes leave telltale marks in tree rings that allow the trained eye to draw conclusions about storm paths, intensities and subsequent regrowth patterns, even if the storm was in the early 20th century. More astonishing is Doyle's use of computer modeling to study 19th century hurricanes. By combining two existing modeling techniques - HURASIM and MANGRO - Doyle has reconstructed the impact of hurricanes on south Florida's mangrove communities dating back to 1886.

link to larger Hurricane Andrew image Courtasy of NOAA

Hurricane Andrew
Hurricane Andrew, the Category 4 storm that pummeled the Louisiana mainland with 130-mile per hour winds in 1992, provided Doyle and fellow NWRC ecologist Bob Keeland an opportunity to investigate not only the storm's structural impact on south-central Louisiana's wetland forests, but also the recovery process. Keeland continues to pursue the question of survival and recovery after Hurricane Andrew into the new century by examining delayed tree mortality, the extent to which trees surviving Andrew's initial onslaught succumbed in the following decade.

Another area of interest for Keeland and his research team is the role played by changes in post-Andrew microhabitats, namely the tip-ups and accompanying depressions left when an entire tree is blown down and its root system exposed. By analyzing soil samples from tip-up mounds and long-term observation of tip-up sites themselves, Keeland has learned much about how these micro-disruptions affect surrounding plant diversity and succession.

NWRC investigator Elijah Ramsey studies the effect of hurricanes on vegetation in a more virtual sense. For example, by using Advanced Very High Resolution Radiometer (AVHRR) images gleaned from orbiting National Oceanic and Atmospheric Administration (NOAA) platforms, Ramsey compared the known infrared profiles of previous years to the months immediately following Hurricane Andrew. His study provided fellow researchers with a good idea of post-Andrew changes in vegetative biomass and leaf surface area, along with a better understanding of the natural recovery process.

Hurricane Georges
Six years after Andrew, Louisiana's Gulf of Mexico Coast was dealt another blow by Hurricane Georges, a storm that also battered Puerto Rico, Haiti, Cuba, Florida, Mississippi and Alabama. Especially hard hit were Louisiana's Chandeleur Islands. The barrier island complex is New Orlean's first line of defense and acts as a natural deterrent against the damaging - and sometimes deadly - storm surges that regularly accompany hurricanes.

A major wintering habitat for a wide range of birds, including endangered species like the piping plover and brown pelican, the Chandeleurs lost over a quarter of the seagrass beds that are the basis of the islands complex food chain. All told, the damage to the islands was nearly as extensive as 1969's deadly Category 5 storm, Hurricane Camille. The chain's recovery, already thwarted by sea-level rise and the lack of sediments necessary to re-establish them, will largely depend on the frequency and intensity of future storms.

Hurricane Mitch
Currently, most of NWRC's international hurricane research is centered upon the mammoth Category 5 storm of 1998 known as Hurricane Mitch. Some 20 NWRC researchers are involved in the Hurricane Mitch recovery effort, partnered with dozens of additional USGS scientists and numerous U.S. and Central American academics. While the storm struck much of Central America, Honduras was hit with an unprecedented ferocity that laid waste to three of its principal industries: shrimping, tourism and agriculture.

Of particular concern is the Honduran shrimp industry. When the turbid and nutrient-rich waters of Honduras flooded agricultural valleys made their way to the coastal aquaculture farms and the Gulf of Fonseca, these areas experienced sediment deposits and algae blooms that eventually led to a declining shrimp population. Those shrimp that did survive, however, did so at the expense of severely stressed immune systems, and when the deadly white spot virus appeared in the Gulf of Fonseca shortly afterwards, it was met with so little resistance that the already reduced shrimp population was all but wiped out.

With the virus now a seemingly permanent feature in the population, NWRC biologist Jill Jenkins is assisting Honduran scientists and shrimp farmers in their efforts to repopulate their waters. Having isolated the enzyme prophenoloxidase as a telltale indicator of the virus, Jenkins went on to develop a color reagent field kit so that diseased shrimp could be identified without laboratory assistance. And slowly but surely, the Honduran shrimp industry is on the rebound.

Also of concern are the Honduran mangrove forests that, along with coral reefs and seagrass beds, make up the barrier reef complexes typically found in the Caribbean. On the bay island of Guanaja, hundreds of acres of mangroves were completely leveled by Hurricane Mitch. Following this large-scale destruction, the mangrove roots that once bound the submerged soil decayed, allowing the soil to collapse so that normal tidal levels were suddenly too deep to allow for normal regrowth. Hence, mangrove recovery now demands labor-intensive hand reseeding and careful long-term monitoring.

Fortunately for the Honduran effort, NWRC plant ecologist Karen McKee has been studying the effects of sea-level rise on mangrove habitat stability in nearby Belize for some 15 years. By examining core samples, McKee is reconstructing the habitats past, learning how historical fluctuations in the intertidal levels have affected mangrove systems. Her data have provided a wealth of information to those shaping the mangrove recovery in Honduras after Hurricane Mitch.

McKee's work demonstrates why scientific data should not exist in a vacuum. Thats why another facet of NWRC's mission is to disseminate its hurricane findings to both the public and scientists through reports to Congress, scientific journals, technical reports, fact sheets, and the NWRC Web site. Sometimes dramatic hurricane findings become part of a breaking news story. Then the Center finds the Associated Press, the New York Times, and CNN clamoring for video and interviews. (See sidebar story on NWRC's Tommy Michot.)

Whether at home or abroad, at ground level or with the assistance of satellite platforms, understanding the impact of hurricanes and the recovery processes are among NWRC's most important ongoing research programs. And if there's been anything whatsoever learned about hurricanes, it is that there will most certainly be a next time.

See Also Hurricane Lili Special Feature - 10/10/02

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