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:

　　Give a human face to environmental issues;Empower people to become active agents of sustainable and equitable development;Promote an understanding that communities are pivotal to changing attitudes towards environmental issues;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.”

　　关于世界环境日世界环境日系由联合国大会于1972年确立，旨在纪念斯德哥尔摩人类环境会议的召开。

　　世界环境日, 设立于每年6月5日，是联合国最重要的纪念日之一，旨为提高世界人们的环保意识和增强政治上的影响力。

　　环境日日程包括：

　　从人类角度看待环境议题;鼓励人们在可持续和可平衡发展中成为活跃的一份子;促进人们理解社区处于环境问题中心枢要位置;主张伙伴关系，以保证各国及人民能享有一个更加安全繁荣的未来.

　　2009年世界环境日的主题是：“你的地球需要你 – 联合国际力量，应对气候变化”。这反映了各国在180天后举行的关键气候协商会议上共同达成新政的紧迫性，及体现了解决贫困问题和提高森林管理的内在联系。

　　今年主办国为墨西哥，它显示了当今拉丁美洲在对抗气候变化，以及碳交易市场中不断上升的地位。

　　墨西哥同样也是环境署“十亿棵树”项目的积极参与方。从总统到平民的支持使得这个国家承诺且种植了高达全球目标25% 的树木。墨西哥也对其占全球的1.5%的温室气体排放做出应对气候变化承诺。

　　墨西哥总统 Felipe Calderon表示世界环境日的庆典活动将“更进一步表达出墨西哥管理自然资源和应对21世纪最大挑战之一——气候变化的决心”。