In Observations

It’s a classic June morning in the Dorchester marshes: hawks on the hunt, ospreys fishing and dragonflies mating as daylight nears its peak of almost 15 hours on the summer solstice June 21.

Changes in elevation in the landscape, almost imperceptible to the eye, express a lush mosaic of grasses and shrubs, each responding to its tolerance for more or less saltwater on the tidal floods. From wren to sparrow to swallow, from blackbird to rail, a symphony of birdsong further enriches the scene.

But it’s the notes missing today that occupy ecologist David Curson. They are silences that shout alarms about these marshes’ future in an era of climate change and sea level rise.

You can’t find much better saltmarsh in these parts than the square mile or so of wetlands here on the western rim of Fishing Bay, owned by the Chesapeake Audubon Society. They extend back from Cedar Creek on either side of a rutted dirt track, quite likely “the wildest, remotest marsh place in Chesapeake Bay one can drive to,” Curson says.

Automatic recorders deployed here to listen for black rails, a shy, robin-sized marsh dweller, haven’t picked up one’s call in three years. It is the fastest declining marsh bird in Maryland, down by 91 per cent since 1991.

“They need the highest (and driest) portions of the marsh, near the forest edges, and we think they may be getting squeezed into small areas by increasing flooding, where foxes can just pick them off,” the wildlife ecologist says.

The forest edge itself is changing dramatically here, and around low-lying Dorchester in general, oaks dying out entirely, pines that are more salt tolerant thinning, then dying, rotting away. In early morning light it is like a band of ghost forest between marsh and living trees.

While he was not anticipating a black rail, Curson was certain he could show our film crew some pretty little saltmarsh swamp sparrows, marked by orange eye stripes and a yellow to buff colored breast—“pretty colorful as little brown birds to,” he says.

But after half an hour: “well this is a first for me. . . in this marsh, in the peak of breeding season, not to see one. This is my go to spot; but maybe not any longer.”

Sparrows are all around us, singing and clinging prettily to tall, slender reeds that sway in the northerly breeze. They are seaside sparrows, about eight times as common overall as saltmarsh sparrows in surveys of Chesapeake region marshes.

Seasides are doing all right, Curson explains, because they are more generalists as to habitat requirements. Saltmarsh sparrows only nest low to the ground in spartina patens, or salt marsh hay, that occupies the driest portions of the marsh. At Farm Creek marsh today we see expanding areas of black needlerush, a species that can stand more tidal flooding, increasingly islanding and shrinking patches of patens. Seasides can utilize needlerush, saltmarsh sparrows cannot.

The latter bird’s rapid decline—nine per cent a year—is a clear indicator that Chesapeake marshes are getting wetter. Climate science predicts that the great bulk of Dorchester’s 91,000 acres of wetlands will disappear by 2100 as sea level rises and land subsides.

That would be a problem far greater than for just the tiny saltmarsh sparrow. Globally there are five vertebrate species wholly dependent on saltmarshes, and three occur in the Chesapeake—the seaside and saltmarsh sparrows, and the state’s official reptile, the diamondback terrapin.

Additionally, tidal wetlands have immense value in protecting against storm surges, filtering pollution running off farms and developments, and as vital nurseries for the young of fishes and crabs. Harder to quantify, but surely no less important is the sheer beauty we’re experiencing out here on this fine June day.

Chesapeake Audubon, along with state and federal environmental agencies, is fighting back. They have identified some 25,000 acres of saltmarsh, including Farm Creek marsh, that runs in a roughly horseshoe shape around the top of Fishing Bay. It includes much of the most intact marsh in Dorchester, with a good diversity of bird species.

A variety of projects there will try to buy this marsh more decades of health as the rest declines to rising tides and erosion. Chesapeake Audubon is going to extend a tidal creek into some stagnant ponds, hoping to breathe life into an area that could afford the saltmarsh sparrow more habitat. Another place, high marsh patens grass is going to planted soon on 40 acres of marsh that has been ‘raised’ almost half a foot by pumping sediments onto it from the channel of the nearby Blackwater River.

An often-voiced strategy for retaining saltmarsh is to leave undeveloped the uplands that border it, to leave room for the marsh to ‘migrate’ inland as tides rise.

It’s a valid concept, Curson says, “but it’s not always easy or elegant.” Around Dorchester the dying forest of the marsh’s upland edges is often taken over by an invasive subspecies of reed, phragmites, which has inferior habitat value. ‘Phrag’ simply outcompetes the native marsh.

Interestingly, in Europe where phragmites has occurred for millennia in large acreages, that has allowed a full suite of bird species to co-evolve with it. Although the Chesapeake does have a native variety of phragmites, it was never dominant to foster such a full-fledged ecosystem.

Down on the Farm Creek marsh this day it is hard to grasp the changes in the land that are coming. But a map from just a century ago shows a post office here where the road now just falls away into mud and shell at Cedar creek. Ditches in the high marsh and the adjacent woods make it clear that back then a lot of this was farmland.

In the haze across Fishing Bay to our east, the modestly elevated trees on Elliott’s Island appear like a distant mountain range—it is just so horizontal, so low, so level in these parts. A few inches of rise in the water comes inland hundreds of yards. It is both the charm and fate of Dorchester.

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