From Dipnote, the State Department blog:

On April 22, people all over the world will celebrate Earth Day 2009 through various programs, activities and events. However, for the nearly 200 employees in the Bureau of Oceans, Environment and Science (OES), every day is Earth Day as we work diligently to promote diplomacy through advancing environmental stewardship, encouraging economic growth, and promoting social development around the globe to foster a safer, more secure and hopeful world.
 
These lofty goals are carried out through programs and activities concerning infectious diseases, biodiversity, natural resource conservation, climate change, access to water, ocean and polar affairs, and science and technology cooperation.

Earth Day has a personal meaning to everyone who celebrates and participates in it - for me, it has significance for several reasons. First, I spent part of my youth working on my family's organic farm in Lebanon, learning the value of the earth in a deep sense. Second I became involved in activism canvassing for an environmental organization, which eventually led to a career in politics working to advance progressive causes. Finally, my grandfather, father and I were born on or within a couple of days of April 22. I lost them both over the past few years and honoring their birthdays/memories coincides with a day that is especially meaningful for my father, who was a prominent environmentalist in the Middle East.