Five times in our planet's history, adverse conditions have extinguished most of life.

Now, scientists say, life on Earth could be in trouble again, with some even saying we could be entering a sixth mass extinction.

No credible scientist disputes that we are in a crisis regarding the speed at which nature is being destroyed.

But could we really be on track to lose most life on Earth?

Human-caused climate change, changes in land use and pollution are rapidly transforming the planet, making it harder for species to adapt and survive.

Reverse nature's decline or there is no future - UN

The United Nations' biodiversity chief says global talks under way in Montreal are the "last chance" to reverse the destruction of the natural world.

"Biodiversity is the foundation of life. Without it, there is no life," Elizabeth Maruma Mrema stated.

But she is worried about the amount of work still needed for the 196 countries to reach an agreement.

Deforestation: Which countries are still cutting down trees?

World leaders have pledged to end and reverse deforestation by 2030.

But in Brazil's Amazon rainforest it has hit its highest level in over 15 years - and progress elsewhere is challenging.

Brazil: Illegal logging continues

Some 60% of the Amazon rainforest is in Brazil, and it plays a vital role in absorbing harmful CO2 that would otherwise escape into the atmosphere.

World leaders will meet at the UN in New York later for more talks to save the world's oceans from overexploitation.

The UN High Seas Treaty has been through 10 years of negotiations but has yet to be signed.

If agreed, it would put 30% of the world's oceans into conservation areas by 2030.

Campaigners hope it will protect marine life from overfishing and other human activities.

Two-thirds of the world's oceans are currently considered international waters, which mean all countries have a right to fish, ship and do research there. But only 1.2% of these high seas, as they are referred to, are protected.

Catastrophic climate change outcomes, including human extinction, are not being taken seriously enough by scientists, a new study says.

The authors say that the consequences of more extreme warming - still on the cards if no action is taken - are "dangerously underexplored".

They argue that the world needs to start preparing for the possibility of what they term the "climate endgame".

They want UN scientists to investigate the risk of catastrophic change. According to this new analysis, the closest attempts to directly understand or address how climate change could lead to global catastrophe have come from popular science books such as The Uninhabitable Earth and not from mainstream science research.