Australia is reverting to "a frontier mentality", with rising rates of deforestation lifting carbon emissions and placing at risk almost 2000 species including the country's iconic koala populations, scientists say.

As many as 400 scientists and four scientific societies are expected to sign a declaration on Friday warning that land-clearing rates are again picking up. Eastern Australia has become the only rich nation to feature among the 11 global deforestation hotspots, they will say.

"Worldwide the most important issue for conservation is habitat loss," Richard Kingsford, director of the Centre for Ecosystem Science at the University of NSW and also Australian president of the Society for Conservation Biology – one of the signatories to the declaration. Threats extend from woodland clearing to the draining of wetlands and the trawling of the oceans, he said.