Sir David Attenborough has called on world leaders to do more to protect nature.
He made his plea as 65 heads of state and government, including the UK's, signed a global pledge to reverse losses in the natural world by 2030.
Addressing the virtual United Nations event, he said world leaders had a chance to make a difference.
A recent BBC documentary, presented by Sir David, issued a stark warning about the extinction crisis and its effects.
"If ever we needed a strong signal from world leaders, for people like you, that we are going to solve this, then this is now," he told the delegates.
Last year, a UN report found that around one million species are now threatened with extinction.
Hunting, habitat destruction and other human activities are pushing a rich array of animals to the edge of oblivion. Human encroachment on the habitats of wild animals also increases the risk of outbreaks of new disease.
During the virtual event, the UK Prime Minister Boris Johnson announced a commitment to protect an extra 400,000 hectares of countryside to support the recovery of nature.
He promised that the government will increase the amount of protected land in the UK from 26% at present to 30% by the end of the decade.
Mr Johnson said countries must turn "words into action" and "agree ambitious goals and binding targets".
"We cannot afford dither and delay because biodiversity loss is happening today and it is happening at a frightening rate," he said.
"Left unchecked, the consequences will be catastrophic for us all.
"Extinction is forever – so our action must be immediate."
Wildlife groups welcomed the announcement but said the UK is one of the world's most nature-depleted countries, with a quarter of native mammals threatened with extinction, including wild cats and red squirrels.
World leaders have often come together to strike deals over climate change, but a top level commitment on nature is much rarer.
Environmentalists are delighted – they say nature is in freefall and urgently needs protection as roads, railways, housing and farmland cover the Earth.
But they say Boris Johnson must lead by example. They point out that around half of existing Sites of Special Scientific Interest in the UK are in poor condition, many through a lack of funding.
What's more, measures to protect wildlife in the Environment Bill are becalmed in the Commons for want of parliamentary time.
Campaigners say if the UK is really taking nature seriously it must avoid trade deals that damage wildlife.
It must also clamp down on imports of food that have caused environmental destruction overseas – such as beef farming in the Amazon.
Craig Bennett, chief executive of The Wildlife Trusts, said "a much greater level of urgent action" was needed to put nature into recovery, including rescuing wildlife sites currently in decline.
The government figure of 26% includes national parks and areas of outstanding natural beauty (AONBs), which are more about how our landscape looks as opposed to the state of nature within them, he said.
He told BBC News: "The reality is at best what's being managed for nature at the moment is only 10%. Even according to the government's own advisers on nature, they say half of that is in a poor condition, so it's nearer 5%. We've got a mountain to climb if we're really going to put nature into recovery in this country and reach the Prime Minister's target by 2030. "
He added that the UK needs to do a much better job of managing the sites that already exist as well as connecting spaces for nature that are not currently protected under the planning system or environmental laws.
The Prime Minister has signed up to the Leaders' Pledge for Nature, which includes commitments to prioritise a green recovery followinRead More – Source
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