More than 26,000 species of animals, birds, plants and fish will this week be added to the list of those in serious danger of extinction. Thousands of species including the common hippotamus are to be added or moved up the so-called "red list" drawn up by The World Conservation Union (IUCN).
The alarming study by the union, one of the most authoritative pictures of world flora and fauna, will make clear that global warming and human activity is responsible.
The report will confirm that the common skate, once abundant around Britain, has been virtually wiped out. The fish is still stocked by some supermarkets and fishmongers, but there is increasing pressure on them to ban it in the same way that cod has been removed from many retailers' shelves.
Sharks, skates and rays are all thought to be vulnerable. Around 20 per cent of sharks are in increasing danger of extinction, the study says. The giant devil ray, similar to a manta ray, is often accidentally caught in nets intended for tuna and other fish.
David Sims, senior research fellow at the Marine Biological Association Laboratory at Plymouth, said that one of the main problems with sharks and rays was that they bore live young so that they reproduce more slowly. "Global fisheries are having a massive effect on population. Some of the nets they use could engulf St Paul's Cathedral," he said.
The new research by the IUCN is the result of two years' work by scientists all over the world and adds to the picture revealed in the union's last report in 2004 which said that 15,589 species faced extinction - 7,266 animals and 8,323 plants and lichens.
While the latest analysis confirms the plight of the polar bear - because climate change threatens its Arctic habitat - more surprising was the threat to the common hippo. Researchers at the IUCN found that biggest problem was posed by poachers killing the creatures for the ivory in their teeth.
One of the creatures predicted to die out is the Yangtze river dolphin or Baiji. It is thought that just 30 remain and that the chances of breeding-age pairs meeting is extremely low.
Chris Butler-Stroud of the Whale and Dolphin Conservation Society, said that the animal was in effect extinct.
The endangered species in the 2004 report included one- third of amphibians and half of all freshwater turtles. At least 15 species had died out over the previous two decades and another 12 survived only in captivity.
Many more, however, are thought to have become extinct without having been recorded. A conservative approach to declaring species lost means that others, which are not yet formally classed as extinct, have probably died out.
Among 3,330 species newly assessed as threatened in 2004 included the fabulous green sphinx moth, from the Hawaiian island of Kaua'i, and the African begonia from Cameroon. Most of the new additions in 2004 were amphibians, joining the red list after the Global Amphibian Assessment that revealed one in three species of frog, toad, newt and salamander were under threat.
The Jambato toad from Ecuador, the golden toad from Costa Rica and the kama'o bird from Hawaii were among the species declared extinct over the past two decades.
Britain had nine critically endangered species - the category at greatest risk - including the slender-billed curlew and the sociable lapwing (both rare visitors here) and Spengler's freshwater mussel. Another 49 species are classed as endangered or vulnerable, including the Atlantic cod and the Scottish wildcat.
Between 1.6 million and 1.9 million species are known to science, but the total is usually estimated at between 10 million and 30 million - and many of those described and classified are poorly understood.