The ferns, flowers, shrubs and grasses of Cadillac Mountain have a tough enough time surviving the elements, but the biggest threat of all may be the pounding of constant foot traffic on Acadia National Park’s busiest and highest summit. Consulting botanist Jill E. Weber gives us a tour of the research plots atop the peak, explaining the multi-year project to bring back the greenery on Cadillac, after limited success in earlier years with physical barriers, ropes and signs.