New research suggests that sometimes trying to completely eliminate a problematic non-native species may cause more harm than good. European green crabs arrived on the eastern shores of North America in the early 1800s, likely as ship ballast stowaways or affixed to boat hulls. They found their way to the continent’s western shores by the 1980s, and they’ve caused trouble in every new ecosystem they invade. Please share this article - Go to very top of page, right hand side, for social media buttons. Wherever green crabs ( Carcinus maenas) land, scientists have documented them decimating food webs by devouring benthic invertebrates that provide nourishment for shorebirds, fishes and other species. Over the years, they have eaten their way onto a list of the world’s top 100 most unwanted species.