This date was established by the UN General Assembly in 1972 and has been celebrated annually by the world community ever since.

The move was prompted by a petition signed by 2,200 scientists and cultural workers from 23 countries on May 11, 1971, to the UN Secretary-General.  They warned humanity of the unprecedented threat posed by environmental pollution.  "Either we end the pollution or it ends us!"  This issue was discussed in the petition.

 It is now a public holiday that aims to unite efforts to conserve natural resources.  It is celebrated in various countries in the form of marches and parades, bicycle tours and "green" holidays.

 The theme for 2021 is Ecosystem Restoration.  2021 is an opportunity to reconsider our efforts and start working together for a sustainable future.

 The decade will end in 2030, which is what the Sustainable Development Goals are the deadline for, and what scientists call the last chance to prevent irreversible climate change.