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Plastic pollution has killed half a million hermit crabs that confused trash for shells

Cleaning up the plastic in the ocean
Cleaning up the plastic in the ocean 26:53

Dead whales beach themselves with hundreds of pounds of plastic in their stomachs. Turtles can't breathe because plastic straws get stuck in their nostrils. Birds are mistaking plastic for food, feeding it to their hungry offspring. 

Now another sea creature is discovering the devastating effects of plastic pollution: hermit crabs. Garbage that has washed ashore has killed more than half a million hermit crabs on remote islands.

According to a recent study in the Journal of Hazardous Materials, an estimated 570,000 hermit crabs die after climbing into plastic debris, confusing it for empty shells every year. It is considered to be the first study quantifying the population impacts caused by plastics on any species. 

Researchers studied strawberry hermit crab populations on the Cocos (Keeling) Islands in the Indian Ocean and Henderson Island in the South Pacific, both of which are littered with millions of pieces of plastic. Researchers made the discovery after finding a staggering 451 million pieces of plastic between the islands, the majority of which was buried beneath the sand.

Hermit crabs killed by plastic debris on remote islands by IMAS - Institute for Marine and Antarctic Studies on YouTube

Plastic debris in the ocean can entangle sea creatures and be ingested by them unknowingly. But on land, it can act as both a barrier and a trap to countless populations. 

When plastic reaches the beach, it creates a trap for hermit crabs searching for food or water that may be found in the containers. Once crabs enter these slippery vessels, it's impossible for them to escape. 

Hermit crabs are not born with their own shells, searching for new shells each time they outgrow one. When one of them dies in a plastic container, it emits a smell to tell others that a shell is available, unknowingly luring more creatures to their untimely deaths, creating a "gruesome chain reaction."  

"The very mechanism that evolved to ensure hermit crabs could replace their shells, has resulted in a lethal lure," researchers said. 

Crabs play crucial roles in tropical ecosystems, aiding in forest growth and development through the soil. Reductions in crabs may significantly impact plant expansion, scientists said. 

Over 500,000 hermit crabs on the Cocos (Keeling) Islands died after climbing into plastic debris ANDREW FIDLER

"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," lead researcher Dr. Jennifer Lavers from the institute for marine and Antarctic studies at the University of Tasmania in Australia said in a statement.

Researchers individually examined the plastic debris on both islands, and the number of dead crabs found trapped. They found a single container containing a staggering 526 crabs. 

"These results are shocking but perhaps not surprising," Lavers said. "It is inevitable that these creatures will interact with and be affected by plastic pollution."  

A loss in hermit crabs affects more than just the health of tropical environments. They play an important role in the economic facets of marine ecosystems that humans rely on for fishing, recreation and tourism. 

"The solution is twofold," explained researcher Dr. Alex Bond from the U.K.'s Natural History Museum. "The first is reducing our reliance on plastic in general. We can do some of that through, for example, using reusable drinking bottles. Equally a lot of these bottles that are already out in the ocean are a result of leaks in waste management systems. Secondly, we need to find those leaks and prevent that escape from proper waste management getting into the ocean."

The smooth surface of plastic means that the hermit crabs cannot escape once they have fallen in.  Natural History Museum London
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