MIAMI, July 1, 2009 - In the first study of its kind, Florida International University scientists, along with an international team of researchers, have discovered a troubling acceleration of seagrass loss across the globe, threatening the immediate health and long-term sustainability of coastal ecosystems.
The team has compiled and analyzed the first comprehensive global assessment of seagrass observations and found that 58 percent of the world's seagrass meadows are currently declining.
Seagrasses profoundly influence the physical, chemical and biological environments of coastal waters. A unique group of submerged flowering plants, seagrasses provide critical habitat for aquatic life, alter water flow and can help mitigate the impact of nutrient and sediment pollution.
"In South Florida, where seagrass beds are particularly widespread and important, growing human populations are increasing the pressure on seagrass meadows," said co-author James Fourqurean of the Southeast Environmental Research Center at FIU. "With 45 percent of the world's population living on the 5 percent of land adjacent to the coast, pressures on remaining coastal seagrass meadows are extremely intense. As more and more people move to coastal areas, conditions only get tougher for seagrass meadows that remain."
The assessment, published in the Proceedings of the National Academy of Sciences on June 29th, shows an acceleration of annual seagrass loss from less than 1 percent per year before 1940 to 7 percent per year since 1990. Based on more than 215 studies and 1,800 observations dating back to 1879, the assessment shows that seagrasses are disappearing at rates similar to coral reefs and tropical rainforests.
The team estimates that seagrasses have been disappearing at the rate of 110 square-kilometers (42.4 square-miles) per year since 1980 and cites two primary causes for the decline: direct impacts from coastal development and dredging activities, and indirect impacts of declining water quality.
"A recurring case of ‘coastal syndrome' is causing the loss of seagrasses worldwide," said co-author William Dennison of the University of Maryland Center for Environmental Science. "The combination of growing urban centers, artificially hardened shorelines and declining natural resources has pushed coastal ecosystems out of balance. Globally, we lose a seagrass meadow the size of a soccer field every thirty minutes."
The article was authored by 14 scientists from the United States, Australia and Spain, including Dennison and Jim Fourqurean.
The assessment was conducted as a part of the Global Seagrass Trajectories Working Group, supported by the National Center for Ecological Analysis and Synthesis (NCEAS) in Santa Barbara, California, through the National Science Foundation.
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