An Indiana University professor says the doom-and-gloom predictions for the Gulf oil spill's effects on coastal wetlands are premature. "In fact, we cannot know the true effects until after the oil has stopped flowing," said Christopher Craft, the Duey-Murphy Professor of Rural Land Policy in the School of Public and Environmental Affairs.
"At this point, the effects of the oil probably are limited to the above-ground vegetation," Craft said. "The roots that contain food reserves that enable the shoots to re-sprout seem to be unaffected. With chronic and repeated exposure to oil, though, the roots could die and the marsh surface collapse, since the roots hold the marsh and soil together. This could lead to disintegration of the marsh as it will convert to open water."
But, Craft explained, the wetlands, which are home to a wide variety of birds, reptiles, amphibians, and insects -- key components to the food web -- have been disintegrating for many years.
"Coastal Louisiana's wetlands have been under siege for a century or more," he said. "The Mississippi River delta is sinking as a result of natural and human-caused activities. Delta regions naturally sink over time as the soft sediments that are deposited by river flooding consolidate and compact. The landscape is stable as long as fresh sediment is deposited by the annual river floods. However, human activities such as construction of dikes and levees that separate the river channel from its wetlands starve the marshes of sediment needed to maintain their elevation, and the land sinks.
"In addition, dredging to maintain navigation channels, along with construction of oil and gas pipelines across the marshes, promotes saltwater intrusion, kills marsh vegetation, and decomposes soil organic matter that is essential for maintaining marsh surface elevation. On top of these threats, rising sea level caused by climate change may push these wetlands to the brink of survival."
The solution has been to reseed vast areas of wetlands in coastal Louisiana to restore wetland habitat. "But this succeeds only under certain conditions," Craft said. "Planting vegetation is generally more successful than seeding, but it is much more expensive and -- in this situation -- is extremely difficult since the potentially affected area is so vast."
Craft, who teaches courses in wetlands ecology, restoration ecology, and applied ecology, said nature is undoubtedly resilient. "If the oil leak is stopped, these wetlands can bounce back. If it continues for many more months, the recovery becomes increasingly uncertain."
Craft's research focuses on wetland restoration, nutrient enrichment and eutrophication, carbon sequestration and effects of climate change. He served as president of the Society of Wetland Scientists (2008-2009), an international organization devoted to sound wetland science, management, and stewardship, and as chair of Division S10, Wetland Soils, of the Soil Science Society of America (2003-2004). He can be reached at (812) 856-1837 or by e-mail at ccraft@indiana.edu.