A University of Queensland-led study involving researchers from three continents has found habitat destruction still far outstrips habitat protection across many parts of the planet.
Associate Professor James Watson of UQ's School of Geography, Planning and Environmental Management and the Wildlife Conservation Society said the published study revealed more than half the planet could now be classified as completely converted to human-dominated land use.
"An area of 4.5 million square kilometres, or about two thirds the size of Australia, has been converted to human-dominated land use in the past two decades alone," he said.
"As a consequence of past and recent habitat loss, almost half of the world's ecoregions now must be classified at very high risk, as 25 times more land has been converted than protected.
"These highly converted and poorly protected ecoregions occur across all continents, and dominate Europe, south and south-east Asia, western South and North America, western Africa, and Madagascar."
Associate Professor Watson said the researchers assessed rates of habitat conversion versus protection at a 1km resolution across the world's 825 terrestrial ecoregions - areas that contain unique plant and animal communities - since 1992.
He said it showed there had been considerable gains in global efforts to increase the size of protected areas, but alarming levels of habitat loss persisted.
Dr Oscar Venter, of the University of Northern British Columbia, said it was time political leaders recognised that simply chasing protected area targets while ignoring the impacts of rampant habitat loss was not a good solution for much of the world's imperiled species.
"We need to specifically target protected areas to places where habitats are disappearing, before it is too late," he said.
The researchers identified 41 ecoregions across 45 nations that are in a 'crisis state', where humans have converted more than 10 per cent of the little remaining habitat in the past two decades.
"These crisis and at-risk ecoregions are clearly the places where targeted conservation interventions need to be prioritised," Associate Professor Watson said.
"But this means a rethink in how nations do conservation planning.
"Nations tend to place protected areas in remote locations, where nobody else is vying to convert the land.
"This does not help save threatened biodiversity, and we must urgently start strategically placing new protected areas in zones that will be destroyed without conservation action."
The researchers from a range of universities and NGOs made their report in the international journal Conservation Letters.
This week 196 signatory nations of the Convention of Biological Diversity meet in Cancun, Mexico to discuss their progress towards averting the biodiversity crisis.