How close did you pay attention to the landscape the last time you went for a hike in a national park? Did you notice the variety of trees or plants, the birds, the insects? Could you tell where there had been a fire or a flood? More subtly, could you see where the nutrient sinks in the ecosystem were? Most of us probably can't answer that last question, but researchers at Isle Royale National Park have uncovered some intriguing contributions to the park's biodiversity.

Most of us head to national parks to walk across the landscape, but for those skilled at diving, some treasures otherwise lost to history can be found. In the waters surrounding Isle Royale National Park, for instance, are a number of wrecks that date back to the late 1800s.

Change is under way in the Great Lakes, the source of 84 percent of North America’s fresh water and more than 20 percent of the world’s supply. It is a progressive sweeping change that threatens to greatly transform the ecosystems of these inland seas by warming their waters and supplanting native species with harmful invasives. And it is a change that ultimately may threaten the viability of the common loon and dozens of other birds that depend on the lakes.