June 5, 1972, marked the opening of the Stockholm Conference of the Human Environment. Every year since, June 5 has been recognized as World Environment Day.
CNN and BBCNews both feature stories on the changes in the environment since that first World Environment Day 33 years ago. Now we have the benefit (or the added perspective) of having had satellites with cameras up in our orbit for three decades; and so we can view pictures of the dramatic changes humans have made upon the landscape in that short time.
You can view side-by-side photos on the CNN website, posted with this article on the new "One Planet Many People" atlas: http://www.cnn.com/2005/TECH/science/06/04/un.atlas.reut/index.html
This year's World Environment Day is focusing on cities (no surprise, given the dramatic changes in urban sprawl evidenced in the atlas photography) and the possibility of sustainable development, or "green cities." Almost half the world's population resides in urban areas. A third of those live in slums and "squatter settlements." The UN estimates that 60% of people will live in urban areas by 2030. Not surprisingly, more urban areas and increased population concentrations in those areas signal increases in pollution and environmental destruction for the natural resources necessary to keep the expansion occurring. You can read the BBC's feature on this at http://news.bbc.co.uk/2/hi/science/nature/4610761.stm
While at the BBC site, be sure to investigate their sidebars, particularly the Changed Earth links. Here, you can find side-by-side pictures chronicling the disappearance of glaciers in the past century -- photographic evidence of a warming planet. Very dramatic stuff.