For the past seven years, scientists have been alarmed by the mysterious death of marsh grasses on Cape Cod, which is transforming expanses of lush green wetlands into lumpy mudflats with the appearance of Swiss cheese.
Work over the past few years has provided strong evidence that the marshes are being eaten away by a particular crab, called Sesarma reticulatum, whose appetite for cordgrass is leaving marshes vulnerable to erosion. The work is also revealing the possibility that human disturbances may have set off the chain of events that caused the crabs’ hungry assault, in turn endangering some of the world’s most important ecosystems.
“One of the pretty scary things is the leading edge of these marshes is the front-line defense for sea-level rise,’’ said Mark Bertness, a biology professor at Brown University who has been working intensively to under stand so-called die-off on the Cape for three years. “They are hurricane buffers and nursery grounds to all kinds of shellfish and finfish, and buffers from run-off — an important filtering system.’’
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