Henderson Island could be a paradise. The remote island in the South Pacific offers secluded beaches and blue sea. But the uninhabited island, which is part of the Pitcairn Islands, has gained notoriety: Henderson Island is considered one of the world's largest densities of plastic garbage.
In a study in 2017, researchers had sounded the alarm and counted tons of plastic washed up on the beaches. Up to 670 plastic parts lay on a square meter of beach. She was washed ashore by the South Pacific Whirlwind, one of the big garbage whirlpools floating in the oceans.
The consequences of the plastic mountains for wildlife on land, the researchers showed now in another study. According to an investigation in the "Journal of Hazardous Materials", more than half a million hermit crabs have been killed by the garbage on Henderson Island and the Cocos Islands in the Indian Ocean, another hotspot for alluvial plastics. On average, researchers found one to two dead animals per square meter of beach.
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While touring the local sandy beaches, Jennifer Lavers from the University of Tasmania's Institute for Marine and Antarctic Research (Imas) first discovered that there were a lot of open plastic bottles or similar containers on the beach. Inside, hermit crabs crept around, and there were also some dead animals inside. Together with colleagues from the Natural History Museum in London, the researchers wanted to find out more.
As the scientists report, in many cases the animals were unable to crawl out of the plastic containers once they were crawled inside. If the opening pointed upwards, the hermit crabs could no longer escape and die. The problem is aggravated because the crabs were attracted by the smell of decay. Because not all animals have their own shell. Therefore, they react to the smell of dead conspecifics. It is a signal that a dwelling has become free.
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Henderson Island: No one, waste everywhereIn larger containers, therefore, there was a veritable mass extinction: The researchers discovered sometimes more than 500 crayfish per container. The problem is very treacherous because one animal is enough to trigger a chain reaction, said Alex Bond of the Natural History Museum in a Guardian report.
Hermit crabs play an important role in the ecosystem of tropical regions. They transport seeds with their shells and thus contribute to the spread of plants. They also aerate and fertilize the soil.
According to Bond, plastic waste can cause considerable damage not only in the sea but also on land. The problem has been underestimated so far. Because the study shows that even a single plastic bottle can become a deadly case for terrestrial animals.
The amount of dead animals could have serious consequences for the population size of the crayfish on the islands. In order to find out if the problem also exists in other places on earth, further studies would be necessary.