But whereas before the sand had always returned--carried ashore by the prevailing summer currents--to cover the exposed stumps, after 1998 the stumps remained exposed. For the first time in 1,600 years, the stumps are weathering 15 years of continuous exposure, deteriorating in the elements. They are covered in barnacles, pounded by the relentless surf and tide. Scientists aren’t sure why, only that this period of exposure is unique. The leading hypothesis is our changing climate.