Corals and seaweed have joined the ranks of threatened species, and more apes and reptiles are now facing extinction according to the World Conservation Union, which warns of a "global extinction crisis".

The conservation group's annual Red List of threatened species, published today, found that the extinction crisis had escalated in the last year with 16,306 species now at the highest levels of extinction threat, equivalent to almost 40% of all species in the survey.

A quarter of all mammals, a third of all amphibians and one in eight birds on the 2007 IUCN Red List are in jeopardy.

More than 180 species have been added since 2006 to the ranks of those classified as endangered, critically endangered or vulnerable.

IUCN director general Julia Marton-Lefèvre warned that this year's list showed how efforts to protect species were inadequate and that a concerted effort by all levels of society was needed to prevent their widespread extinction.

"The rate of biodiversity loss is increasing and we need to act now to significantly reduce it and stave off this global extinction crisis," she said.

Despite reports of its demise, the Yangtze river dolphin is classified as critically endangered (possibly extinct). Although the last documented sighting of the dolphin was in 2002, further surveys are needed before it can be definitively classified as extinct, said the IUCN. A possible sighting last month is being investigated by Chinese scientists.

The IUCN report had just one success story. Mauritius Echo Parakeets have been downlisted from the "critically endangered" category to "endangered" after conservation measures led to 139 birds bred in captivity being successfully released into the wild.

Deputy head of IUCN's species programme, Jean-Christophe Vié, said an improvement for only one species was "really worrying" in the light of government commitments such as the 2010 target to slow down the rate of biodiversity loss.

Corals were assessed and added to the Red List for the first time, and two corals found in the Galapagos have entered the list in the "critically endangered" category and one in the "vulnerable" category. The rise in sea temperature caused by the effects of El Niño and climate change are identified as the main threats.

Ocean warming also threatens seaweeds around the islands, with 10 classified as critically endangered, six of which are highlighted as "possibly extinct". The seaweeds are also affected by overfishing which removes predators from the food chain, resulting in an increase in sea urchins, which overgraze the algae.

Gorillas and orangutans face a particularly grim future after the discovery that more than 60% of Western Lowland Gorillas in Africa have been wiped out by the Ebola virus and the commercial bushmeat trade, and forest clearance for oil palm plantations, along with illegal logging, continue to seriously threaten the survival of orangutans in Sumatra and Borneo.

The Gharial crocodile has been uplisted from "endangered" to "critically endangered" following the discovery that there are less than 200 breeding adults left in the wild. The report said that excessive irreversible habitat loss in Nepal and India following the construction of dams and irrigation canals had wiped out more than half the crocodile's population in the last decade.

Other particularly threatened animals include the Eastern Chimpanzee, found in central and east Africa, which faces habitat loss, poaching and disease, and Speke's Gazelle whose numbers have been decimated by hunting, drought and overgrazing across the grasslands of Somalia and Ethiopia.

Two Mexican freshwater turtle species and a rattlesnake species are among the 700 reptiles added to the list this year after a major assessment in Mexico and North America. The Santa Catalina Island Rattlesnake, caught by illegal collectors and eaten by feral cats, is the most endangered new entry.

The brightly-coloured Banggai Cardinalfish, collected for the international aquarium trade, is one of 1,200 endangered fish on the list.

Vultures in Africa and Asia are among the most endangered birds with five species, including the Red-headed Vulture and the Egyptian Vulture, reclassified this year. Lack of food, due to habitat loss, a reduction in grazing mammals and the increasing use of drugs to treat livestock are to blame for the vultures' rapid decline.

The Red List examines just over 40,000 species, around 12% of the 15m species in the world.

Around 70% of the world's assessed plants are on the 2007 Red List. The Woolly-stalked Begonia, a Malaysian herb, was the only species declared extinct this year bringing the total number of extinct species to 785. A further 65 species now exist only in captivity.

Chair of the IUCN's species survival commission, Holly Dublin, said it showed how environmentalists alone could not save endangered animals and plants.

"The challenge of the extinction crisis also requires attention and action from the general public, the private sector, governments and policy makers to ensure that global biodiversity remains intact for generations to come," she said.

The IUCN report stressed how the rapid disappearance of species had a direct impact on people's lives. Declining freshwater fish, for example, deprived rural poor communities of their major source of food and their livelihoods.

Jane Smart, head of the IUCN's species programme, said: "Our lives are inextricably linked with biodiversity and ultimately its protection is essential for our very survival."

Conservation charity, WWF, said the increasing number of threatened species on the IUCN Red List demonstrated how the planet was being pushed to its limits.

"We're at code red," said Dr Mark Wright, chief scientist at WWF-UK. "The plight of the world's species is a mirror on the state of the planet. Species are under enormous pressure as we systematically destroy their habitat or overexploit them for our increasingly demanding lifestyles.

"We urgently need to reverse this trend and start living within the planet's natural resources - not just for the wellbeing of these threatened species but also for our own."

© 2007 The Guardian