World Environment Day (WED) was established by the UN General Assembly in 1972 to mark the opening of the Stockholm Conference on the Human Environment.
Commemorated yearly on 5 June, WED is one of the principal vehicles through which the United Nations stimulates worldwide awareness of the environment and enhances political attention and action. The day's agenda is to:

1. Give a human face to environmental issues;
2. Empower people to become active agents of sustainable and equitable development;
3. Promote an understanding that communities are pivotal to changing attitudes towards environmental issues;
4. Advocate partnership which will ensure all nations and peoples enjoy a safer and more prosperous future.

The theme for WED 2009 is 'Your Planet Needs You-UNite to Combat Climate Change'. It reflects the urgency for nations to agree on a new deal at the crucial climate convention meeting in Copenhagen some 180 days later in the year, and the links with overcoming poverty and improved management of forests.
This year’s host is Mexico which reflects the growing role of the Latin American country in the fight against climate change, including its growing participation in the carbon markets.
Mexico is also a leading partner in UNEP's Billion Tree Campaign. The country, with the support of its President and people, has spearheaded the pledging and planting of some 25 per cent of the trees under the campaign. Accounting for around 1.5 per cent of global greenhouse gas emissions, the country is demonstrating its commitment to climate change on several fronts.
Mexican President Felipe Calderon states that the WED celebration will “further underline Mexico's determination to manage natural resources and deal with the most demanding challenge of the 21st century – climate change.”