The crabs' appetite for cordgrass is leaving the marshes vulnerable to erosion and endangering some of the world's most important ecosystems, the Boston Globe reported Tuesday.
Biologist Mark Bertness of Brown University has been working for the past three years to understand the die-off of Cape grasses.
Early findings indicate that predators of the Sesarma crab are less prevalent in marshes disturbed by human activity, especially fishing.
Bertness says that suggests recreational fishing has reached a "tipping point," altering nature's balance by depleting the crab's enemies and allowing them to thrive in greater numbers.
"It's looking like a classic story of humans altering one link in the food chain and everything going nutty," says Stephen Smith, a plant ecologist at the Cape Cod National Seashore.