'Happy World Environment Day' photo (c) 2011, Nisa yeh - license: https://creativecommons.org/licenses/by-sa/2.0/

“World Environment Day (‘WED’) is celebrated every year on 5th june to raise global awareness of the need to take positive environmental action. It is run by the United Nations Environment Programme (UNEP).”

You might be interested in The Best Resources For World Environment Day.