A major new study warns that the natural world is deteriorating faster than ever as a direct result of human activity, putting the foundations of economies, health and well-being at risk.
Here are some answers to key questions about the study.
It is a global assessment of the state of nature, including wild land and marine species, habitats and domesticated breeds of plants and animals, and is the first such report since 2005 and the most comprehensive of its kind.
It has been compiled by 145 expert authors from 50 countries over the past three years, with inputs from another 310 contributing authors.
The report comes from the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES), an intergovernmental body set up under the UN with more than 130 countries as members.
In the words of the chairman of the IPBES, Robert Watson, the evidence from the 15,000 references used in the report paint an "ominous picture".
Nature is declining at an unprecedented rate, with one million of the world's eight million species at risk of extinction.
The declines are a result of human activity, namely our use of the land and seas, direct exploitation of wildlife, climate change, pollution and introduction of invasive species, and will continue without action to tackle these problems.
For example, the report warns that around 500,000 of the world's 5.9 million land-based species do not have enough habitat to survive long term, and will become extinct, many in decades, without action to restore their habitat.
It is not just bad news for wildlife - undermining the natural systems humans rely on will harm the economy, health, food security and well-being.
The report outlines scenarios for the future, and finds that "transformative change" is needed across the economy and society to reverse the declines.
That includes sustainable farming which also looks after wildlife, restoring and connecting up damaged habitats such as natural forests, cutting food waste and promoting sustainable diets.
There is a need to enforce environmental regulations, tackle illegal logging, expand protected areas, and prevent damage to wetlands and peatlands.
In the seas, overfishing needs to be tackled, marine protected areas created and pollution reduced, and in cities, more green space is needed.
The two are interconnected: the IPBES report finds that climate change is the third biggest threat to wildlife and will continue to grow.
It also warns that changes to the way we use land is not only the biggest threat to wildlife, but also a major problem for the climate, as around a quarter of greenhouse gas emissions come from clearing land, growing crops and using fertilisers.
But it also says that tackling climate change, for example by planting trees and restoring forests to capture carbon dioxide emissions from the atmosphere can help wildlife too, if the focus is on native species, not plantations.
Like the Intergovernmental Panel on Climate Change (IPCC) which produces major reports on climate science for governments, the summary of the study has been approved by government officials meeting in Paris before publication.
That means they have already accepted the findings, including the damage to economies that failing to tackle the problem will cause.
They have also recognised that vested interests which benefit from existing subsidies for damaging practices or a lack of regulation will oppose the kind of change needed, but can be overcome for the public good.
Pointing to the world's first comprehensive deal to tackle climate change, the Paris Agreement struck in the French capital in 2015, Mr Watson called for the report's publication to start a "Paris moment" for nature.
The study will be used as the basis for negotiations under the UN Convention on Biological Diversity on new targets to tackle wildlife losses from 2020, which will take place in China next year.
But the findings of this report show that previous efforts to halt wildlife loss have failed, highlighting the need for much greater ambition.
Environmental group WWF is calling on governments to create a new "global deal for nature and people", similar to the Paris Agreement.