Smithsonian researchers develop models to assess wetland healthSeptember 17, 2007Healthy wetlands perform vital ecological functions in a watershed. But assessing their condition and ability to perform those functions is not easy, especially as wetlands are disappearing fast due to human encroachment. In a special issue of the journal Wetlands, Smithsonian scientists report a promising method of wetland assessment that will help environmental managers quickly take stock of wetlands across an entire watershed. Tools for this kind of rapid watershed-scale assessment-relying on a few easily measurable key factors-have been previously unavailable to managers. In three papers, Dennis Whigham, Donald Weller and Thomas Jordan of the Smithsonian Environmental Research Center and their colleagues present the results of a large-scale study that combines field studies and remote-sensing data to assess the ecological functioning of wetlands in a landscape.
The researchers based their study on an approach previously developed for assessing individual sites, called the Hydrogeomorphic (HGM) approach, in which ecological conditions are inferred from readily observable indicators, such as plant species present and the degree of human disturbance. "We took these methods for assessing wetland functions and expanded them to a whole-landscape scale, which is something that has not been effectively done before," said Whigham, who coordinated the project. "These days, most land managers are not asking how to understand what is going on in an individual wetland, they want to manage resources at a much larger scale." Wetlands are important buffers for flood control, can absorb pollutants and excess nutrients and provide critical habitats for many plants and animals, including some threatened and endangered species. For this study, the researchers focused on non-tidal wetlands in the Nanticoke River watershed of Maryland and Delaware. Draining into the Chesapeake Bay, the Nanticoke system is one of the most biologically important and wetland-rich watersheds in the mid-Atlantic region. Wetlands are found along streams (riverine wetlands) and in poorly drained uplands called "flats." During the first year of the project, the researchers visited wetlands of both types, taking field measurements and observations according to the HGM protocol at more than 100 sites. They used the data to formulate models to rate the condition of the sites, which ranged from nearly undisturbed to highly degraded. The sites were chosen according to a statistical procedure developed by the Environmental Protection Agency to ensure that they were representative of the entire landscape. For a subset of the sites, the researchers took a closer look at one important ecological function of wetlands: the cycling of nutrients, particularly nitrogen. Many watersheds are overloaded in nutrients due to runoff from agricultural fields and other sources. The result is diminished water quality. But soils in healthy wetlands contain bacteria that remove excess nitrogen by a process called denitrification and can restore water quality. "We found that you can predict denitrification potential from some fairly easy-to-measure properties of the soil, such as percent organic matter or pH," said Jordan, who led this portion of the study. As a final step, the researchers took the results of the field assessments and compared them with digital maps and remotely sensed data, such as satellite land cover images. "The idea was to develop statistical models that would successfully predict what was observed in the field," said Weller, whose lab performed the analysis. "Once you've developed the models, you then can assess additional wetlands without having to go out and sample them," he added. While the models cannot predict the precise conditions at a given site, they can provide enough information to identify potentially degraded areas and help guide management priorities in a watershed. Smithsonian | |||||||||||||||||||||
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Related Wetlands News Articles Evaluating ecosystem services Environmental conservation efforts have traditionally focused on protecting individual species or natural resources. Scientists are discovering, however, that preserving the benefits that whole ecosystems provide to people is more economically and environmentally valuable. At the Annual Meeting of the Ecological Society of America (ESA), ecologists will explore the application of ecosystem services approaches to conservation. Rising energy, food prices major threats to wetlands as farmers eye new areas for crops Critical food shortages and growing demand for bio-fuels and hydro-electricity due to high fossil fuel prices rank among the greatest threats today to the preservation of precious wetlands worldwide as farmers and developers look for new areas for agriculture, energy crop plantations and hydro dams. Mangroves key to saving lives The replanting of mangroves on the coasts of the Philippines could help save many of the lives lost in the 20-30 typhoons that hit the islands annually. Scripps study sets high economic value on threatened Mexican mangroves The ecological value of coastal mangrove forests in Mexico has been apparent to marine scientists for years. Now, for the first time, researchers have used a wide-ranging compilation of fisheries landings, the official record of fish catches, to place an economic price tag on that value. New population of highly threatened greater bamboo lemur found in Madagascar Researchers in Madagascar have confirmed the existence of a population of greater bamboo lemurs more than 400 kilometers (240 miles) from the only other place where the Critically Endangered species is known to live, raising hopes for its survival. Massive greenhouse gases may be released as destruction, drying of world wetlands worsens: UN Leading world scientists convene in Brazil July 21-25 amid growing concern that evaporation and ongoing destruction of world wetlands, which hold a volume of carbon similar to that in the atmosphere today, could cause them to exhale billows of greenhouse gases. Plan to conserve forests may be detrimental to other ecosystems Conserving biodiversity must be considered when developing plans to reduce greenhouse gas emissions from deforestation, researchers warn in today's edition of Science. Woody and aquatic plants pose greatest invasive threat to China Although China currently has fewer invasive woody plants than the United States, China's potential for invasion by nonnative trees and shrubs is high, according to an article in the May 2008 issue of BioScience. UMCES-led research team quantifies nutrient pollution reductions from urban stream restoration A team of researchers led by University of Maryland Center for Environmental Science researcher Dr. Sujay Kaushal has been among the first able to quantify the amount of excess nitrogen removed from an urban stream during environmental restoration projects. Better regional monitoring of CO2 needed as global levels continue rising Monitoring Earth's rising greenhouse gas levels will require a global data collection network 10 times larger than the one currently in place in order to quantify regional progress in emission reductions, according to a new research commentary by University of Colorado and NOAA researchers appearing in the April 25 issue of Science. More Wetlands News Articles |
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