One million of the world's species are now under threat of extinction, according to the biggest-ever review of the state of nature on Earth.

Key points: The report, which draws on 15,000 scientific and government sources, says human use of land and sea resources are mostly to blame

The report, which draws on 15,000 scientific and government sources, says human use of land and sea resources are mostly to blame The decline in nature is happening at rates that are unprecedented in human history, the UN report reveals

The decline in nature is happening at rates that are unprecedented in human history, the UN report reveals More than 40 per cent of amphibian species, almost 33 per cent of reef-forming corals and more than a third of all marine mammals are threatened

The UN-backed report was three years in the making and was based on systematic reviews of 15,000 scientific and government sources.

Among a vast number of alarming findings is that the average population size of native species in most habitats on land has fallen by at least 20 per cent, mostly since 1900.

More than 40 per cent of amphibian species, almost 33 per cent of reef-forming corals and more than a third of all marine mammals are now under threat.

"We are eroding the very foundations of our economies, livelihoods, food security, health and quality of life worldwide," said Sir Robert Watson, the chair of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), which put together the report.

The IPBES has 132 nation-members and is known as the equivalent of the Intergovernmental Panel on Climate Change (IPCC), but for biodiversity.

Human expansion and exploitation of habitats to blame

The report says that human use of the land and sea resources are mostly to blame, followed by direct exploitation of animals, climate change, pollution and invasive species.

More than a third of the world's land surface and nearly 75 per cent of freshwater resources are now devoted to crop or livestock production, while urban areas have more than doubled since 1992.

Scientists from the IPBES have been meeting to finalise the report in recent days. ( Supplied: IPBES )

Meanwhile, 300-400 million tonnes of heavy metals, solvents, toxic sludge and other waste is dumped into the world's waters every year.

The decline in nature is happening at rates that are unprecedented in human history.

"It's like reading a paper that says the natural world is in catastrophic decline and there is a chance that this catastrophe will take us all down with it," said Tim Beshara, federal policy director of Wilderness Society.

"Humanity is causing a slow-motion apocalypse of the natural world and that's getting faster and faster as time goes on."

In Australia, part of the problem is rapid deforestation, said Professor James Watson, the director for the University of Queensland's Centre for Biodiversity and Conservation Science.

"We are world leaders in habitat clearance, vegetation clearance — we clear more land than just about every country on the planet, especially for cattle farming," he said.

The rapid losses are also evident in our cities.

"Thirty, forty years ago koalas were a common species," said Professor Watson.

"Every single suburb in Brisbane, for example, had very healthy populations of koalas. Right now, only one suburb in Brisbane has a koala population, and that's a very small one."

Decades ago, koalas were a common species in suburbs. ( ABC News: Emma Siossian )

"Fundamentally, we're sleepwalking into an extinction crisis. We're not talking about the biosphere in the way that we need to. Nature is getting eroded in a dramatic way and a loss of natural capital means that humans will suffer in the long run."

Sir Robert Watson said there must be transformative change to human civilisation if we are to avoid the extinction crisis.

"By transformative change, we mean a fundamental, system-wide reorganisation across technological, economic and social factors," he said.

Australia 'missing in action' on conservation

Next year is a big year for global conservation. The signatories to the Convention on Biological Diversity, which is the global treaty meant to safeguard biodiversity, are scheduled to meet and sign a new post-2020 strategic plan.

Professor Watson said it's an opportunity to reset the clock and design a global deal for nature and biodiversity.

Human use of land and sea resources has been a major factor in the biodiversity crisis, according to the IPBES. ( Supplied: IPBES )

"The sad thing is Australia has gone missing in these negotiations, they haven't even turned up to the last major international negotiations around this matter, and as you are seeing in the federal election, biodiversity is just not even mentioned," he said.

"That's a shame because Australia is one of the few mega-biodiverse countries around the world — we have more species than just about every other country."