The report is calling for a sweeping overhaul of the way we produce and consume almost everything, especially food.
Humanity is rapidly destroying the natural world upon which our prosperity - and ultimately our survival - depends, according to a landmark UN assessment of the state of nature released Monday.
Changes wrought by decades of pillaging and poisoning forests, oceans, soil and air threaten society "at least as much as climate change," said Robert Watson, who chaired the 132-nation meeting that validated a Summary for Policymakers forged by 450 experts.
One million animal and plant species face extinction, many within decades, they reported.
Alarmingly, the accelerating pace at which unique life-forms are disappearing - already tens to hundreds of times faster than during the last 10 million years - could tip Earth into the first mass extinction since non-avian dinosaurs died out 66 million years ago.
Around 10 per cent of insects face extinction, more than 30 per cent of reef-forming corals and marine mammals, and more than 40 per cent of amphibians.
In the short term, humans are not at risk, said Josef Settele, a professor at the Helmholtz Centre for Environmental Research in Germany and co-chair of the UN Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES).
"In the longer term, it is hard to say," he told AFP. "If humans do go extinct, Nature will find its way, it always does."
Halting and reversing these dire trends will require "transformative change" - a sweeping overhaul of the way we produce and consume almost everything, especially food, the report concluded.
"We are eroding the very foundations of our economies, livelihoods, food security, health and quality-of-life worldwide," said Mr Watson.
"By transformative change, we mean a fundamental, system-wide reorganisation."
Global sustainability goals for 2030 will not be met otherwise, the authors say.
The sobering report comes after three years of work from 145 expert authors, building on a 2005 study and assessing global changes over the past 50 years.
Of the world's estimated 5.9 million land-based species, more than 500,000 have insufficient habitat for long-term survival.
The report, which is based on 15,000 scientific and government sources, says the biggest drivers of environmental destruction are changes in land and sea use, exploitation of organisms, climate change, pollution, and invasive species.
Some of the sobering figures include that plastic pollution has increased tenfold since 1980 and up to 400 million tonnes of industrial waste are dumped in the world's waters every year.
There are 400 ocean "dead zones" caused by fertilisers entering coastal ecosystems - a combined area larger than the UK.
The report notes that 60 billion tonnes of resources are extracted every year, nearly double the amount in 1980.
In Australia three native species have become extinct in the last decade and scientists say 17 more could be wiped out in the next 20 years.
The Australian Conservation Foundation's Basha Stasak wants the federal government to implement a goal to protect 30 per cent of earth's land and waters by 2030.
"The global assessment is clear - there are limits to the destructive human activity nature can withstand. We are not just pushing those limits, we are breaking them at unprecedented rates," she said.
"Our next federal government must strongly argue for a global deal that has clear measurable targets and obligations that halt the extinction, ensure species populations recover and protect critical ecosystems."
The pushback from "vested interests," he added, is likely to be fierce.
Drawing from 15,000 sources and an underlying 1,800-page report, the executive summary details how our species' growing footprint and appetites have compromised the natural renewal of resources that sustain civilisation, starting with fresh water, breathable air, and productive soil.
A vicious cycle
An October report from the UN's climate science panel painted a similarly dire picture for global warming, and likewise highlighted the need for social transformation "on an unprecedented scale" to cap the rise in temperature at 1.5 degrees Celsius (2.7 Fahrenheit).
The global thermometer has already gone up by 1C, and on current trends will rise another 3C by century's end.
Climate change and biodiversity loss, it turns out, feed off each other in a vicious cycle.
Deforestation and industrial agriculture are major drivers of species and ecosystem decline, but also account for at least a quarter of man-made greenhouse gas emissions.
Trees release planet-warming carbon dioxide when cut down, and the destruction each year of tropical forests covering an area the size of England shrinks the vegetal sponge that helps to absorb it.
Global warming, in turn, is pushing thousands of animals and plants out of their comfort zones, and intensifies the kind of heatwaves and droughts that recently fuelled unprecedented fires in Australia, Indonesia, Russia, Portugal, California and Greece.
The overlapping drivers of global warming and biodiversity loss point to shared solutions, but there is potential for policy conflict too, the new report cautioned.
Plans to green the global economy reserve a crucial role for burning biofuels and locking away the CO2 released, a technology known as BECCS.
But the huge tracts of land needed to grow energy crops on this scale - roughly twice the size of India - would clash with the expansion of protected areas and reforestation efforts, not to mention food production.
For the first time, the UN body has ranked the top five causes of species lost and the degradation of nature.
By a long shot, the first two are diminished or degraded habitat, and hunting for food or trade - often illicit - in body parts.
All but 7 per cent of major marine fish stocks, for example, are in decline or exploited to the limit of sustainability despite efforts by regional management organisations to fish sustainably.
Global warming is third on the list, but is likely to move up.
"We can see the climate change signal getting stronger really, really quickly," IPBES co-chair Sandra Diaz, a professor at the National University of Cordoba in Argentina, told AFP.
Numbers four and five are pollution - 400 million tonnes of heavy metals, toxic sludge and other waste are dumped into oceans and rivers each year - and alien species, such as rats, mosquitoes, snakes and plants that hitch rides on ships or planes.
"There are also two big indirect drivers of biodiversity loss and climate change - the number of people in the world and their growing ability to consume," said Mr Watson.
The heavily negotiated text does not set benchmarks for progress or "last chance" deadlines for action, as does the 2018 climate report.
Nor is the panel mandated to make explicit policy recommendations.
But it does point unmistakably to actions needed: reduce meat consumption, halt deforestation in tropical countries, discourage luxury consumption, slash perverse subsidies, embrace the concept of a low-growth economy.
The report will "serve as a basis for redefining our objectives" ahead of a key meeting of the UN Convention on Biological Diversity in China in October 2020, said co-author Yunne Jai Shin, a scientist at the Research Institute for Development in Marseilles.