Sandbar, St. Clair River, Canada, 2002Photograph by Jay DickmanThe Great Lakes hold a fifth of Earth's surface fresh water, and they've shrunk dramatically. For some, like this child playing in the St. Clair River, that means miles of newly exposed shoreline and sandbars to explore. For others, like those in the shipping and fishing industry, lakefront property owners, and water-dependent animal species, it's a disaster in the making.