Image caption The king cobra is the largest but certainly not the only threatened East Asian snake

East Asia's status as the world's main "extinction hotspot" is confirmed in the new Red List of Threatened Species .

Snakes such as the king cobra, the world's largest venomous serpent, are increasingly threatened by hunting for meat, skin and the pet trade.

The Red List was unveiled at the Rio+20 sustainable development meeting .

The International Union for the Conservation of Nature, which compiles the list, says it shows the importance of nature for human wellbeing.

One of the themes of the Rio meeting, which comes 20 years after the iconic Earth Summit here, is the "green economy" - an economy that uses the services nature provides more wisely, and safeguards them.

"A sustainable future cannot be achieved without conserving biological diversity, not only for nature itself but also for all seven billion people who depend on it," said IUCN director-general Julia Marton-Lefevre.

"The latest Red List is a clarion call to world leaders gathering in Rio to secure the web of life on this planet."

Two thousand new species have been assessed for this edition of the Red List, bringing the total to 63,837.

Overall, the statistics are little changed: 41% of amphibians, 33% of reef-building corals, 25% of mammals and 13% of birds languish on the risk list.

While the biggest threat globally is loss of habitat, the picture for the newly assessed East Asian snakes is somewhat different.

Rapid economic growth and consequent demand for natural resources are putting increased pressure on mammals, plants, reptiles and amphibians across the region.

But for the snakes, deliberate harvesting for food, medicine, skin and the pet trade emerges as a serious issue.

"Paradoxically, the conversion of forest to oil palm plantations, which is so bad for many species, seems to be quite good for some snakes," said Craig Hilton-Taylor, manager of IUCN's Red List Unit.

"That's why a lot of trade is coming from those areas," he told BBC News.

"As long as it's controlled and kept sustainable, that's fine; but once the demand for snakes starts moving into their native habitat, that's a problem."

Snub news

Dr Hilton-Taylor also highlighted the listing of new Asian primates including the Myanmar snub-nosed monkey, which has straightaway gained a Critically Endangered rating.

Image caption The Myanmar snub-nosed monkey is so little-seen that images must be digitally reconstructed

"It was only described last year - in fact, very few people have seen it; in fact it's really known only from camera traps," he said.

The new list includes a number of plants that have been over-harvested for fruit that are used in food and medicine, including two species of turmeric and one of ginger.

The Rio+20 summit is not directly concerned with nature protection - that is the job of other UN organisations such as the Convention on Biological Diversity.

But its focus is on making development more sustainable, urging governments to measure "natural capital", the money locked up in forests, water, plants and animals.

Pollination of plants, for example, is estimated to be worth $200bn to the global economy each year - and as IUCN notes, numbers of some pollinating animals including some bees, bats and birds are falling.

Just before the meeting started, IUCN released its assessment of Amazonian birds, which moved 100 species from lower classes of threat (such as Vulnerable) to higher classes (Endangered or Critically Endangered).

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