[audio:http://wamcradio.org/EarthWise/wp-content/uploads/2014/07/EW-07-10-14-Ecosystems-Need-Predators.mp3|titles=EW 07-10-14 Ecosystems Need Predators]
Salt marshes are extremely important ecosystems. They shield coasts from flooding, they remove pollutants from water, and they are the baby nurseries for many kinds of fish. In recent years, salt marshes in places like the coastlines of New England have been dying off.
There have been many theories offered to explain the cause of the die-off: outbreaks of harmful fungi, pollution, sediments stirred up by boats, and rising sea levels associated with the changing climate.
Recently, ecologists at Brown University have reported the results of an experiment designed to test a different theory for what is destroying salt marshes. Based on the evidence from the experiment, the culprit may actually be fishermen. Recreational fishing and crabbing in salt marshes has the effect of removing the top predators from the local ecosystem. When this happens, the prey species, including those that feed on plants, prosper. Growing populations of creatures such as marsh crabs can quickly wipe out marsh plants like cordgrass, which are essential in limiting the erosion that otherwise prevents new plants from growing.
The researchers had noticed that dying marshes tended to be near docks, marinas, or buoys where fishing commonly takes place. With this clue, they deliberately eliminated the predator population in a salt marsh to see if that would trigger a die-off. The resultant degradation of the environment was remarkably fast.
Fishing is not the only destructive force in salt marshes, but identifying it is an important discovery for conservation efforts for these important ecosystems. We need to maintain healthy predator populations.
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When Predators Vanish, So Does the Ecosystem
Photo, posted April 22, 2012, courtesy of Trish Hartmann via Flickr.
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