Eco Engineers: 5 Animals That Can Reshape Earth's Waterways


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Burrowing Crabs
Burrowing crabs trenches along mangrove swamp shorelines so deep they often collapse. Nortondefeis via Wikimedia Commons

It's time to take a break from our own phylum. A number of crustaceans are great diggers, including the so-called fiddler crabs (genus Uca), which shelter in tunnels measuring up to 3 feet (0.9 meters) or more in depth. (The holes are quite a construction project, given the fact that most fiddler species are less than 2 inches (5 centimeters) wide.

And then we've got the "burrowing crabs" of the genus Chasmagnathus. Unrelated to the fiddlers, these guys live in the mangrove swamps, salt marshes and estuaries of eastern Asia. For many years, a South American species formerly known as Chasmognathus granulatus was assigned to this genus, but in 2006, it was reclassified and renamed Neohelice granulata — though, confusingly, some scientists still use the old name.

Often found in the mangrove swamps of Brazil and Argentina, Neohelice granulata is an efficient, deep-digging burrower. Like muskrat holes, the tunnels these small crabs builds are liable to weaken the surrounding turf. On mangrove swamp shorelines, this has the effect of widening tidal creeks, whose mud and clay-based banks are rendered more vulnerable to erosion by the digging invertebrates. And that's just part of the story. Because burrowing crabs have such a pronounced effect on sediment composition, their tunnels can also cause completely new creeks to form within these mangrove systems.

So despite being rather miniscule animals, burrowing crabs can shake up entire waterway networks. Will nature ever cease to amaze us?

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