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Guilty: Crabs are killing N.E. saltmarshes

Two newly published studies by a team of researchers provide ample evidence that the reason coastal saltmarshes are dying from Long Island to Cape Cod is that hungry crabs, left unchecked by a lack of predators, are eating the cordgrass. In one paper, published in the journal PLoS ONE, they provide the results of numerous measurements at 14 sites around Rhode Island’s Narragansett Bay. They sought correlations between the extent of marsh death and evidence of any of several popular hypotheses. The winner by far was runaway herbivory of cordgrass by the Sesarma crab. In the other study, published in the journal Ecology Letters, they directly tested that hypothesis with experiments on Cape Cod. The results were that wherever they protected Sesarma from the pressure of predators, the crabs ruthlessly mowed the grasses down.

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