Extinction threat 'a call to world leaders' at Rio Earth Summit

(CNN) -- Serving as a timely reminder to delegates convening for the Rio +20 Earth Summit, the International Union for Conservation of Nature (IUCN) has published its latest Red List detailing the ongoing threats to biodiversity on the planet. The IUCN assessed a total of 63,837 plant and animal species around the globe which revealed 19,817 of that number are currently threatened with extinction, with 3,947 described as "critically endangered" -- the final classification prior to extinction. A further 5,766 are "endangered," while more than 10,000 species are listed as "vulnerable." "Sustainability is a matter of life and death for people on the planet. 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," Julia Marton-Lefevre, IUCN director general, said in a statement. "(The latest report) is a clarion call to world leaders gathering in Rio to secure the web of life," Marton-Lefevre added. See Also: Can Rio +20 solve world's environmental problems? Amphibious creatures like frogs, toads and newts are the most endangered group with 41% facing extinction. A quarter of all mammals and 13% of bird species are heading towards a similar fate.