"The sea otters are stabilizing [these creek banks] for free in exchange for an all-you-can-eat crab feast."

South of Cape Cod, fiddler crabs and marsh grass have long had a mutually beneficial relationship. It’s a different story in the North, where the harms can ricochet through ecosystems.

Salt marshes act as barriers against storm surges and natural disasters for coastal communities. But rising sea levels are breaking them down.

New research describes how climate change leads to voracious crabs becoming troublesome keystone species in more and more salt marshes.