Australian scientists are calling for the koala to be declared an endangered species, warning that populations have already declined alarmingly and climate change will exacerbate the mammal's plight.

A Senate committee set up to investigate the health and status of the koala has been told that better conservation measures are needed to safeguard the future of one of Australia's best-known native animals, already under pressure from habitat loss and disease. The committee will report to the Federal Minister for Sustainability, Tony Burke, who has the power to list it as endangered.

Where Australia once had millions of koalas, the total population was probably no more than 50,000-100,000, said Dr Clive McAlpine, a landscape ecologist at the University of Queensland. While the situation varies from region to region, and data is patchy, populations have declined by as much as 80 per cent during the past 10 to 15 years in places such as the Gold Coast.

Land clearing for urban development, industry and agriculture has deprived the koala of much of its traditional habitat, while diseases - particularly chlamydia - are also exacting a toll.

The long drought, meanwhile, has affected the koala's food supply because of its impact on eucalyptus trees, whose leaves koalas eat and get moisture from.

Climate change represents another threat, with the mammals ill-equipped to deal with the hotter, drier conditions predicted for southern Australia. "They suffer heat stress and dehydration, so unless they get access to water they virtually drop out of the trees," McAlpine said.

Christine Hosking, who is researching a PhD on the subject at Queensland University, said koalas were unable to cope with successive hot days of more than 30C. She warned that climate change would reduce their range severely, pushing them towards heavily urbanised eastern coastal areas, where there is little habitat available and they face the additional dangers of cars and dogs.

Hosking called for a federal action plan, including better habitat protection and funding for research into a chlamydia vaccine. "This species is supposed to be common, yet it's slipping to extinction under our noses," she said.

McAlpine said: "We need to stop taking the koala for granted and start looking after it."