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| Ted O'Callahan helps his wife, Kim Hubbard, through one of the preserve's wetter areas. |
Mid-afternoon on the
day after Thanksgiving, I went with friends to Mass Audubon’s Daniel Webster
Wildlife Sanctuary in Marshfield. This formerly agricultural property, known to
some locals as Dwyer Farm, is one of my favorite places to walk. Among other
things, it’s expansive, picturesque, and relatively close to home, so it’s the
place I most often bring guests from out of town. It was a chilly day, but
sunny, and so we chose the sanctuary’s wide open fields over other, more woodsy
options.
“Favorite place” aside,
it had been a few years since I’d walked at Daniel Webster. At first it didn’t
seem like much had changed. We made our way around the perimeter of the 600+
acres, strolling past the pond and an observation blind, and into the woods
where a series of boardwalks led us over wetlands and among ice-encrusted
trees. As usual, there was plenty of beauty to observe: the blue sky reflected
on the water’s surface; the rich orange and reds of bittersweet vines; bright
green tufts of meadow grass poking up through the snow.
My companions were
unfamiliar with the property, so while I led them around, I told them what I
knew of its history and geography. How it had been spared from development
decades earlier through a sustained grassroots effort; how it once belonged to nineteenth-century
Senator Daniel Webster; how a portion of the parcel was indeed “sanctuary” for
wildlife and thus closed to the public.
As we neared Fox
Hill, a rise from which – looking toward the ocean -- one can see far down into
the Green Harbor River Valley, I had a vague recollection of an article I’d
read in the local paper a while back . . . something about adjusting the tide
gates in the dike between the harbor and the river – an effort to improve water
flow and reduce flooding. I wondered if there would be a discernible difference
upstream.
We continued our
circuit, traversing another boardwalk through what I remembered – a few years
back – as being mostly-dry marsh grass. Looking down, I was surprised to see
how flooded the marsh was! High tide was still an hour away, but indeed, there
was a lot more water under the walkway than there used to be. So much that I
wondered, when high tide came, whether the boardwalk would be submerged.
At the end of the
boardwalk, there is a grassy path that leads to a short O-shaped trail. If you
go right, you can follow the trail along the water’s edge. If you go left, you climb
up onto a wooden bridge that crosses – and offers a great view of -- the river.
Well, those are the options at low tide, at least! We found the trail pretty-well
swamped; even the few steps to the bridge required careful footing.
Beyond that bridge,
another boardwalk leads through a red maple swamp, to a second bridge and river
crossing. My memories were of at least a foot of clearance between the boardwalk
planks and the water, but again, it seemed that the distance had shortened
dramatically. An inch or two more of incoming tide would have put the walkway
under water.
We completed our excursion
with dry feet and – for me at least – a lot of questions. Was this a fluke
occurrence, or are the water levels in the river and its wetlands this high all
the time now? Has there always been such a tidal influence within the wildlife
sanctuary, or is this new? Is the water saltier now, due to greater tidal
influence, or is it just higher? What does this mean for the vegetation along
the banks of the river, and the wildlife?
I directed my
inquiries to Sue MacCallum, Director of Mass Audubon’s South Shore Sanctuaries,
and Jay Wennemer, the Town of Marshfield’s Conservation Agent. Here’s what I
learned: Yes, indeed, the tide gates at the Brant Rock Dike are now routinely
adjusted to control the flow of water into and out of the Green Harbor River.
In the past, there were issues with sedimentation, flooding, and especially in
summer, stench. Now the town can – for example -- open the gates to allow more
water to flow in, or close them to protect the river valley from a coastal
storm. Thanks to this joint effort by the town and several state agencies, the
marsh and river are healthier now. Similar projects have taken place with great
success at Straits Pond in Hull and Cohasset, and
Musquashcut Pond in Scituate.
According to
Samantha Woods, Executive Director of the North and South Rivers Watershed
Association, “Managing tide gates to work in concert with
nature allows us to reduce the impacts these structures have on the ecology of
the river. Like the removal of dams on rivers, the restoration of tidal flows
changes the landscape that we have come to know in our lifetimes but ultimately
the system is much healthier when we try to mimic what nature intended.”
Sara Grady, Regional Coordinator of the Massachusetts Bays National Estuary Program, is
part of the team that has been monitoring changes in vegetation, fish and
invertebrates associated with this project. She explains, “the changes that
have been seen are primarily that there are estuarine species of plants and
animals (including some salt marsh habitat) upstream of the tide gate now, and
the Phragmites near the tide gate and in the upper tributaries has started to
disappear. In addition, there are places on the MassAudubon property that were
meadow that are transitioning to wetland, particularly the area near the osprey
pole, where there is a (formerly dry) creek that now experiences tides.”
It’s important to
note that none of these are negatives. In fact, according to Wennemer, they are
quite positive, as they vastly improve the ability of a large inland portion of
Marshfield to tolerate storm-related flooding. The landscape will change over time,
but we won’t know for sure in which ways or to what degree until more time has
passed. For me, that’s an intriguing proposition. As the years pass, there will
be fascinating to see what happens at the Daniel Webster Sanctuary.
by Kezia Bacon
January 2015
Kezia Bacon's articles
appear courtesy of the North and South Rivers Watershed Association, a local
non-profit organization devoted to the preservation, restoration, maintenance
and conservation of the North and South Rivers and their watershed. For
membership information and a copy of their latest newsletter, contact NSRWA at
(781) 659-8168 or visit www.nsrwa.org. To browse 15 years of Nature (Human and
Otherwise) columns, visit http://keziabaconbernstein.blogspot.com
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