Are Invasive Green Crabs Saving New England Marshes?

by Owen James Burke


Despite that they may be bringing competition to the native or species of crabs (i.e., the more popular blue crab), this invasive species may actually be rescuing a dwindling salt marsh in Cape Cod, Massachusetts.

It all started in the 1930s and continued into the WWII era when ditches were dug in marshes in an effort to drain mosquito breeding habitats. That, in conjunction with overpopulation and further irrigation of coastal land gave way to low marsh cord grass (as opposed to high marsh grass). Native purple marsh crabs, which feed on cord grass, moved in at about the same their natural predators were being heavily overfished (namely the blue crab and the striped bass). With not much threat of predation, decades-long smorgasbord followed for the purple mud crab, and marshlands were severely depleted.

Enter the European green crab, which has been listed as one of the top 100 detrimental invasive species on the Global Invasive Species Database. Fortunately (in this circumstance), as is the case with many invasive creatures, the green crab is a seriously enduring specimen, and has found the abundant purple mud crab, and are sending them for the deep, or so scientists are beginning to suppose.

So, eco-warriors, before you snuff your nose at the idea of welcoming a foreign, invasive species, consider that, perhaps, this may be the key to reparation and, maybe evolution. Even though the damage done over the past several decades will not be immediately (or ever) repaired by the invasive green crab, there is evidence that it may slow the destruction of the marsh, which is Cape Cod’s only natural and effective buffer from storms and erosions.


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