China's president Xi Jinping says the world must co-operate on climate change

It comes just a week after Xi Jinping promised China - the world's worst polluter and an economic super power - would be carbon neutral by 2060.

In another landmark speech, he told the UN biodiversity summit: "At present there exists an acceleration of the global extinction of species.

"The loss of biodiversity and degradation of the ecosystem pose a major risk to human survival and development.

"It falls to all of us to act together. We need to respect nature, follow its laws and protect it. We need to find a way for man and nature to live in harmony and balance and coordinate economic development and ecological protection."

It came as a new study by the Royal Botanical Gardens at Kew in London collated the findings of 210 scientists from 42 countries.

They estimated forty per cent of plant species are at risk of extinction, hundreds of medicinal plants are threatened and only a tiny fraction of plants are being used for food and fuel.

Professor Phil Stevenson told Sky News: "The attention that is being drawn to biodiversity loss at high levels around the world I think is a really positive thing.

"This report will provide those decision makers, and also individuals at home, with new information and more information on making better decisions about conserving the diversity of plants and funghi."

It seems hard to re-imagine China as a champion of climate change and biodiversity given the environmental devastation caused by its break-neck speed of economic transformation. So has China really turned over a new leaf?

Isabel Hilton, CEO of China Dialogue, said: "On the analogy of the prodigal son, isn't it better that China has got to the point of understanding how damaging its previous policies were, and is now exerting leadership in a number of ways."

It's easy to make promises but the world will be watching to see whether those with the power actually make a difference on biodiversity and climate change.