A plan to crisscross 110 square miles of swampy landscape in a search for oil promises to test the National Park Service's ability to balance the unimpairment of resources with the "enjoyment of privately owned oil and gas interests" at Big Cypress National Preserve, a nearly three-quarters-of-a-million-acre wildland that nurtures endangered species and filters a good portion of the sheet of water that nourishes the "river of grass" on its way into neighboring Everglades National Park.