I have often argued that environmental cleanliness and wealth tend to follow a U-shaped curve. Early industrialization tends to make air and water quality worse, but increases in wealth and technology over time tend to lead to an improved environment. For example, nearly every air and water quality metric in the US has improved substantially over the last 40 years.
To this end, I saw this chart in another context (Dr. Pielke was discussing the effect of land-use on regional climate changes) but I thought it was an interesting one to illustrate this point, and perhaps start to convince all those 20-somethings of the Obama generation that the world is not, in fact, spiraling ever downwards into economic decay. This is a map of leaf area, bascially an index of forestation, for the Eastern US over the last 400 years. Note the trend reversal since 1920.
I have argued for a while that trying to slam a halt to China's development as part of some misguided environmental effort may in fact achieve the opposite effect, locking China into the low-point of the U-shaped curve just at the point when increasing wealth may be pushing them to start cleaning up.