© KERRY HYNDMANing wetlands with pumps and floodgates
designed to keep water off their land.^4 In
some places the intermittent flooding will
advance, and in others it will stall until the
sea level rises so much that it overwhelms
that infrastructure. “And that’s a big part of
the uncertainty about our future—how are
those things going to be managed?” Bern-
hardt says. “It’s important that the water
movement in this landscape is very much
under human control.”Forests and marshes on the move
At Blackwater, as forested wetland is lost to
rising sea waters, marsh habitat is appear-
ing in its place. Because marshes support
a unique ecosystem containing plant and
animal life and may sequester greenhouse
gases better than open water, marshlands
might be better for the environment than
letting the land become completely inun-
dated. So land managers at the refuge are
working to keep the marsh above water.
One project, for example, involves taking
layers of sediment from the Blackwater
River, a feeder for the Blackwater Pond, and
spraying it out over the marsh. So far, the
team has spread 26,000 cubic feet of sedi-
ment across 40 acres of marsh to raise its
surface four to five inches on average. The
team then planted hundreds of thousands
of marsh grass sprigs to keep the sediment
in place and bolster the marshes’ resilience
to sea level rise.
Around the globe, sea level has been
rising since the peak of the last Ice Age,
about 20,000 years ago, as a result of
melting glaciers adding water to Earth’s
oceans. “These marshes in the heart of the
Blackwater River have been building ele-
vation in response to [that] sea level rise
for almost a thousand years,” Whitbeck
says. But now the marshes can’t keep up.
In addition to the continued melting of the
world’s remaining glaciers, which are dis-
appearing faster than ever, the mid-Atlan-
tic region is sinking, causing it to experi-
ence sea level rise at a rate three to four
times faster than the rest of the terrestrial
world. Artificially raising the marshes
“puts the plant community back in that
sweet spot,” Whitbeck says, “so hopefully
we can get a few more decades out of themSAL T KILLS TREES FROM THE ROOTS UP
Most trees are extremely sensitive to salt, from the roots, which struggle to
take up water from salty soils, to the trunk, branches, and leaves, where high
concentrations of salt ions hinder plants’ cellular processes.
As salinity increases, it can shift the balance from the plant having a higher
relative concentration of dissolved ions to the surrounding soil having a higher
ion concentration. This makes it harder for the plant to take up water against
this strong concentration gradient, leading to water stress that physiologically is
quite similar to drought stress, even if there is plenty of water in the soil.Water
Na+
CL-
Soil