“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).”

Here’s the official site with lots of resources.

Here’s the official video for 2017:

Here’s the official video for 2013:

ESL Holiday Lessons has a…lesson on World Environment Day.

And here are previously posted “The Best…” lists that could be useful:

The Best Sites To Introduce Environmental Issues Into The Classroom

The Best Online Carbon Calculators

The Best Sites To Learn About Climate Change

The Best Resources For World Biodiversity Day (& Endangered Species Day)

World Environment Day 2018: ‘Beat Plastic Pollution’ is a photo gallery from The Atlantic.