Climate change presents world leaders with "life or death" choices, the Ugandan climate activist Vanessa Nakate said on Wednesday as she pressed them to treat it as an urgent crisis.
Poverty, hunger, conflicts, disease and violence against women were some of the knock-on effects she cited.
"The people and the planet must come first before anything else," Nakate said.
"If you do not treat climate change as a crisis then you will not do what is necessary for us to get out of this mess. It is time for leaders to leave their comfort zones and see the danger that we are in and do something about it."
"We need to stop being passive, we need to stop putting each other down and criticising each other," Ayakha Melithafa, a South African climate activist, said.
"We are powerful beyond measure and together we will truly make powerful and effective change."
Vanessa Nakate, a vocal young activist who has demonstrated with Greta Thunberg, was giving the annual Desmond Tutu peace lecture.
In are-recorded speeches due to the coronavirus pandemic, activists warned that the world is entering "the decisive decade" for climate and environment and called for climate justice globally.