Today's Science Times in the New York Times had an interesting piece by Andrew Revkin on the impacts of humans on the oceans. As is so often the case these days with the Times, there were some great graphics (see above). I especially liked the newsprint version of the shipping lanes map since it is a subject I've studied and written about in the past.
Without mentioning GIS by name, Revkin discusses how these maps were generated:
A paper in the Feb. 15 issue of the journal Science is the first effort to map 17 kinds of human ocean impacts like organic pollution, including agricultural runoff and sewage; damage from bottom-scraping trawls; and intensive traditional fishing along coral reefs.
I tried to look up the Science article referred to by Revkin, but I don't have a subscription. It is called "A Global Map of Human Impact on Marine Ecosystems," by Halpern et al., 2/15/2008, p. 948-952, in case you're interested in sleuthing it out.
Another site referred to in the Times piece is the Census of Marine Life. The available map seems to be a work in progress but it is a place to watch for marine data and info.