More than 100 world leaders have promised to end and reverse deforestation by 2030, in the COP26 climate summit’s first major deal.
Brazil – where stretches of the Amazon rainforest have been cut down – was among the signatories on Tuesday.
The pledge includes almost £14bn ($19.2bn) of public and private funds.
Experts welcomed the move, but warned a previous deal in 2014 had “failed to slow deforestation at all” and commitments needed to be delivered on.
Felling trees contributes to climate change because it depletes forests that absorb vast amounts of the warming gas CO2.
UK Prime Minister Boris Johnson, who is hosting the global meeting in Glasgow, said “more leaders than ever before” – a total of 110 – had made the “landmark” commitment.
“We have to stop the devastating loss of our forests,” he said – and “end the role of humanity as nature’s conqueror, and instead become nature’s custodian”.
The two-week summit in Glasgow is seen as crucial if climate change is to be brought under control.
The countries who have signed the pledge – including Canada, Brazil, Russia, China, Indonesia, the Democratic Republic of the Congo, the US and the UK (the full list is here) – cover around 85% of the world’s forests.
Some of the funding will go to developing countries to restore damaged land, tackle wildfires and support indigenous communities.
Governments of 28 countries also committed to remove deforestation from the global trade of food and other agricultural products such as palm oil, soya and cocoa.
These industries drive forest loss by cutting down trees to make space for animals to graze or crops to grow.
More than 30 of the world’s biggest financial companies – including Aviva, Schroders and Axa – have also promised to end investment in activities linked to deforestation.
And a £1.1bn fund will be established to protect the world’s second largest tropical rainforest – in the Congo Basin.
Prof Simon Lewis, an expert on climate and forests at University College London, said: “It is good news to have a political commitment to end deforestation from so many countries, and significant funding to move forward on that journey.”
But he told the BBC the world “has been here before” with a declaration in 2014 in New York “which failed to slow deforestation at all”.
There are reasons to be cheerful about the proposed plan to limit deforestation, specifically the scale of the funding, and the key countries that are supporting the pledge.
It is also very positive that it will try to reinforce the role of indigenous people in protecting their trees. Studies have shown that protecting the rights of native communities is one of the best ways of saving forested lands.
But there are significant challenges.
Many previous plans haven’t achieved their goals. In fact, deforestation has increased since a similar pledge was launched in 2014.
There are often disputes between donors and recipients – Norway suspended funding for an Amazon fund in 2019 in an argument with Brazil’s president.
There are also major questions over how a major financial pledge could be effectively policed.
How can funders verify that forests are actually being protected without spying from satellites or challenging national sovereignty in some way?
And question marks also hang over a key plank of the new plan, which is to try to remove the link to deforestation from consumer goods sold in developed countries.
One aspect is eating meat from animals, raised on imported soy grown on cleared lands. Will governments push companies and consumers to eat less meat to save the world’s most important forests?