In the early days of this blog you've read a lot of talk about externalities, or unintended and unaccounted for costs or benefits from human activity. Well here's an example from a recent AP story (Chemical Contamination in Arctic Linked to Bird Droppings):
...a study by a group of Canadian researchers found that the chemical pollution in areas frequented by seabirds can be many times higher than in nearby regions.
...sea birds, which feed in the ocean but then come back to land, are returning not only with food for their young but with contaminants as well. The contaminants accumulate in their bodies and are released on land.
I'm not sure what this means, but it sure makes efforts at modeling pollution much harder.
