Intensive Logging Created New England's Rich Wetlands

07 January 2011 by Sujata Gupta Magazine issue 2794

THOSE who enjoy the wetlands and seafood of New England's coastline may be surprised by who they have to thank: the loggers of the 18th and 19th centuries. In clearing vast tracts of land, those prolific loggers released so much sand and dirt that open-water bays turned into swamps.

While logging devastated the landscape, it had the opposite effect on the coast. The wetlands it boosted buffer the coastline from storms, stop pollutants in the ocean from reaching the shore, and shelter marine organisms. "No wetlands, no seafood," says Matthew Kirwan of the US Geological Survey in Laurel, Maryland.

For purists who favour returning New England to its natural state - and restoration is a multibillion-dollar endeavour - the theory presents a conundrum. Many New England marshes are much bigger than they were before the arrival of European settlers, says Kirwan, so restoring the environment to a "natural" state would mean losing much of the marshland and its benefits.

To find out how old the marsh in the Plum Island estuary in Massachusetts is, Kirwan dated fossil plant rhizomes - found in marshes but not open water - from 45 sediment cores. The oldest ones were found at the marsh's edge and dated back some 4000 years. In the centre of the marsh, however, the oldest rhizomes were just 200 years old, suggesting that until then Plum Island estuary was half marsh, half open-water bay. The shift to full marsh coincides with an increase in logging, according to historic records. Only that sort of extensive land-use change can account for the bay's filling in, says Kirwan. He presented his findings at the American Geophysical Union conference in San Francisco last month.

The idea that what's bad for the land may be good for the sea is not unique to New England. Studies in the 1980s showed that Chesapeake Bay was built thanks in part to high sedimentation rates caused by logging and land clearance. Agricultural development along the Mississippi river is likely to have contributed to Louisiana's estuaries and bayous, and Kirwan suspects that mining bolstered California's coastal wetlands.

Dorothy Merritts, a geoscientist at Franklin & Marshall College in Lancaster, Pennsylvania, points out that whatever the inadvertent ecological benefits of logging, it still destroyed the coast's original ecosystem. "Many original wetlands were lost," she says.

Source: NewScientist