“Defend the castle!” we would shout as the incoming tide crept its way toward the mound of sand my cousins and I had spent hours piling, sculpting and decorating. Scrambling for cobble, driftwood, seaweed, and frantically digging moats to manage the onslaught of encroaching waves, we played an improvised game of trying to keep our sandcastle from being overtaken by the ocean and destroyed. It was the late 1980s in southern Maine on Drake’s Island in Wells, at the north end of the beach just past the end of the sea wall. For us kids, it was the epitome of summer fun. In 1979, our families had purchased some of the last undeveloped beachfront property in southern Maine, abutting what is now the Wells Reserve at Laudholm. There our parents built dream castles of their own: three modern but modest vacation homes set back 150 feet from the edge of the front dune, elevated 10 feet off the ground atop recycled telephone poles. The outcome of a litigious tussle with the state for building rights made us some lucky kids: the homes had direct access to a wide sandy beach and the Atlantic Ocean right through our backyards. ABOUT THE AUTHOR David Forest is a resident of Wells. But 40 years later, my cousins and I find ourselves playing a much more serious and higher-stakes adult version of that same “defend the castle” game, in the same yet markedly altered place. Erosion and rising sea levels over the past four decades weakened the protective dune system, making our homes more vulnerable to the stronger and more frequent storms of the past few winters. The rate of erosion has gone exponential; after the two “100-year storms” that hit two days apart in January of this year, the dune was obliterated. […]