Almost two years after work began and 10 years after discussions first started, the Custer Gallatin National Forest has finished writing a preliminary environmental assessment examining a proposed land exchange north of Yellowstone National Park. …“The big purpose is wildlife habitat and public access,” Thom said. “That’s a big migration route for that Northern Yellowstone elk herd. …“The acquisition would also conserve important scenic values in the upper Gardiner Basin,” the EA stated, protecting a portion of the narrow section of the Highway 89 corridor to the park’s Northern Entrance, located about 12 miles north of Yellowstone National Park, from subdivision and development.