The UN General Assembly in Sep 2021 will bring countries together at a critical time for marshalling collective action to tackle the global environmental crisis. They will meet again at the biodiversity summit in Kunming, China, and the climate change conference (COP26) in Glasgow, UK. Ahead of these pivotal meetings, editors of health journals worldwide - call for urgent action to keep average global temperature increases below 1.5 degrees C, halt the destruction of nature and protect health. Health is already being harmed by global temperature increases and the destruction of the natural world, a state of affairs health professionals have been bringing attention to for decades. The science is unequivocal; a global increase of 1.5 degrees C above the preindustrial average and the continued loss of biodiversity risk catastrophic harm to health that will be impossible to reverse. Despite the world's necessary preoccupation with COVID-19, we cannot wait for the pandemic to pass to rapidly reduce emissions.