July 28, 2009

Freshwater Crabs Critically Endangered Around the World

Two thirds of all different species of freshwater crabs are at risk of becoming extinct, says a new survey.

That means that freshwater crabs are some of the most endangered of all groups of animals reviewed thus far. This research is the first worldwide evaluation of the extinction danger of any collection of freshwater invertebrates.

Crab species in Southeast Asia are the most vulnerable, mainly due to habitat devastation and pollution.

Scientists from the Zoological Society of London and Northern Michigan University conducted the survey, and released the first World Conservation Union (IUCN) Red List review of the 1280 identified species of freshwater crab.

The researchers discovered that 227 species should be labeled as at risk, endangered or gravely endangered. For 628 other species, not enough information is available to properly evaluate them, said the survey released in the journal Biological Conservation.

The most hopeful scenario is that 16% of every species is endangered, while the worst case scenario implies that the number could be as great as 65%, or two-thirds of every species.

Freshwater crabs are vital to freshwater ecosystems. They eat leaves and algae, while others aid cycle nutrients by consuming huge amounts of detritus.

The crabs are a significant supply of food for animals like herons, kingfishers, monitor lizards, crocodiles, frogs and toads. Mammals that depend on the freshwater crabs include otters, mongooses, civets, wild boar and macaque monkeys.

Since the majority of the species needs clean water to live, they are also outstanding indicators of water quality. However, these species are progressively becoming harmed by habitat devastation.

40 of 50 species that live in Sri Lanka are seriously at risk. These species have a semi-terrestrial life; breathing air, digging burrows and spending their time in both water and land. They are the most endangered, due to the disturbance of their habitats by humans.

Although non have yet gone extinct, some species, like the terrestrial crab Thaipotamon siamese and the waterfall crab Demanietta manii from Thailand, have not been seen for nearly a century, and their habitats have harmed by urban developments.

"We must set clear goals to reverse these trends and ensure that our enduring legacy is not to wipe out the small things that provide us with great benefits, such as nutrient cycling," said Ben Collen, one the survey scientists from the Zoological Society of London, to BBC news.


Image Credit: New Mexico University


On The Net:

Northern Michigan University

IUCN Red List of Threatened Species