A green recovery from the pandemic has been backed by the Global Climate and Health Alliance (GCHA)
The world is facing a "deeper emergency" than coronavirus, the UN chief has warned.
The coronavirus pandemic may already be having an impact on global pollution levels but it is hoped that recovery from the crisis will put the world on track to a greener future.
Online events are being held to mark the 50th anniversary of Earth Day with video messages from Pope Francis, Al Gore, Elizabeth Warren, Zac Efron, Roger Waters, Josh Lucas and Dave Matthews.
United Nations secretary-general Antonio Guterres said the recovery from the pandemic must be turned into a real opportunity to do things right for the future
While the impact of COVID-19 was both "immediate and dreadful" and countries must work together to save lives and lessen the consequences of the pandemic, he said there was "another, even deeper emergency - the planet's unfolding environmental crisis".