On South Padre Island, change happens not just seasonally—from the crowded summer to the quiet winter—but every day, right under your feet. As you drive north through the resort town on State Park Road 100, the beach shops and fried-fish restaurants give way to one of the prettiest features of the island: the sand dunes. Keep going and watch as the small mounds become more abundant and massive—some can reach as high as fifty feet—until the encroaching beach seems to be swallowing the road. Park, walk, and observe (just don’t tread upon the dunes). See any western slender glass lizards darting among the sea oats? The vines of pinkish-purple goat’s-foot morning glories? The next time you come, the scene might look different, notes David Hicks, director of the School of Earth, Environmental, and Marine Sciences at the University of Texas Rio Grande Valley. “Dunes are ephemeral structures engaged in a battle, with the wind trying to move the sand and the plants trying to keep it in place,” he says.