Thousands of years ago, glaciers covered New England, but slowly retreated as the climate warmed naturally (that is, without interference by humans). The meltwater caused sea level to rise. Eight thousand years ago the coastline of Marshfield was six miles out to sea. As the sea level slowly rose, the coastline was inundated, so that now it is only about a mile from the airport. The rise created many of the features that seem like they have always been there: the Green Harbor Marsh and Green Harbor tidal river. But they were not always here. Environments change for myriad reasons, and are changing faster today, as glaciers to the north melt at a faster rate than ever.
Many scientists believe that global warming is accelerated by the huge number of people, domesticated animals, factories, automobiles, trains and other creations that create heat, which rises. The temperature rise seems to be correlated with stronger and more frequent coastal storms and surges. Not everyone agrees on the cause. Yet look at Marshfield for an example, where the sea walls built a few generations ago are no match for recent storms. When the Green Harbor Marsh was a fully functional estuary, it was a shock absorber for storm surges, but its dammed-up condition does not permit it to function naturally. Humans now must adapt by moving out of reach or trying to build resilient walls and systems. Coastal communities face a possible inland move, just as Native Americans slowly did thousands of years ago.
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