Deforestation

I don't know why no one ever thought to do this yet, but you can really see the scale and effect of deforestation with Google Maps or Google Earth. Here is a large area in South America where there is pretty much nothing left. It's important when looking at that to zoom in and out and look at the distance scale in the lower left to understand the magnitude.

End to end, that patch of land is roughly 250-300 miles long.
Colorado is roughly 370 miles wide East-West. 280 North-South.

Yikes.