Importance of hermit crabs

Humble hermit crabs are crucial to terrestrial and marine ecosystems. On land, they disperse seeds and create carbon-rich soil micro-habitats by burrowing and collecting leaf litter, which help forests thrive. Their contributions are particularly important on the Cocos Islands and Henderson Island, which lack native ground predators that would otherwise help with those tasks.

The paper also submits that hermit crabs are an important economic resource: the Cocos Islands are home to at least 26 crab species, including several hermit crab species, which could provide an opportunity for wildlife tourism. So a disruption of hermit crab populations could have both ecological and economic effects.

Hermit crabs are common in coastal environments worldwide. The paper hypothesizes that on beaches where the crabs coexist with heavy plastic debris, there is a risk that they may meet the same fate.

“High concentrations of debris are now being encountered on beaches around the world, many of which are also home to hermit crabs that can be expected to interact with plastic pollution in the same way as those we studied,” Lavers said.

Crabs that became trapped and died inside a plastic drink bottle on one of the Cocos (Keeling) Islands. Image courtesy of Lavers et. al., 2019 (CC BY-NC-ND 4.0).

Kristian Syberg, a marine plastic pollution expert at Roskilde University in Denmark, said the hermit crab study provides a comprehensive impact assessment of plastic debris in heavily polluted sites, or hotspots.

“Through this study it is feasible to say that ‘hot-spot’ areas of macro plastic pollution do pose a risk,” Syberg, who was not involved in the study, told Mongabay.

Syberg said documenting the effect of plastic pollution on wildlife populations is very difficult in locations where knowledge is limited. Nevertheless, he said, “widespread risk from both macro and micro plastics is likely within the next century if current patterns are not changed.”

Some of the 526 hermit crab shells found inside a single plastic container on Henderson Island. Image courtesy of Lavers et. al., 2019 (CC BY-NC-ND 4.0).

Banner image: A strawberry hermit crab (Coenobita perlatus) in the Seychelles. Image by William BKH via Wikimedia Commons (Public domain).


Lavers, J. L., Sharp, P. B., Stuckenbrock, S., & Bond, A. L. (2019). Entrapment in plastic debris endangers hermit crabs. Journal of Hazardous Materials, 387(1). doi:10.1016/j.jhazmat.2019.121703.

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Article published by Rebecca Kessler
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