BBC News
November 2, 2021
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.