The good news: Otters in Alaska’s Prince William Sound seem to have finally rebounded to population levels and life cycles similar to those they enjoyed before the wreck of the Exxon Valdez in 1989. The bad news: The fact that it took this long is just another example of how the impact of oil spills should be measured in decades, not days. Another example: There is still oil from the Exxon Valdez on beaches near the site of the wreck. The oil exists in little pockets protected by boulders and it’s still getting into food webs, at least in very small amounts.