03.2020 | THE SCIENTIST 37MATT KIRWAN
rather than just a few years.” This strategy,
he notes, could be applied to the countless
marshes in the Chesapeake Bay and else-
where that are “drowning in place.”
The issue is a pressing one. Mapping
marsh and forest habitats within the refuge
over time, Whitbeck and colleagues starkly
revealed the thousands of acres of marsh
that have turned into open water over the last
few decades and the thousands more turned
from forest to marsh. Models of sea level rise
predict that by 2050 the refuge could lose
thousands more acres of marsh. In other
words, building up existing marshes won’t
be enough; Whitbeck and his colleagues
also want to predict where the marshes will
move—where forest will turn to marsh—as
sea levels continue to rise.
In a report published a few years ago,
Whitbeck and his collaborators identified
regions that might support marsh move-
ment in the future, what they called marsh
migration corridors. Tw o regions that the
researchers have specifically focused on—
the Nanticoke River at the east end of the
Blackwater Refuge and Coursey Creek
to the west, both of which are a mix of
marsh and forest now—could maintain
nearly 6,000 acres of marsh in the refuge
by 2100.^5 To encourage such marshes to
grow, however, the team has to be mind-
ful of obstacles, such as dead and dying
trees and invasive reed species, that might
impede migration. “Having those standing
snags really precludes a lot of salt marsh
species in the mid-Atlantic from using an
otherwise suitable habitat,” says Whitbeck.
His team has ripped out ghost forest tree
stumps and controlled invasive plants to
bolster the growth of native marsh plants
that serve as high-quality habitat for bird
species such as the black rail and the salt
marsh sparrow. But despite the researchers’
best efforts, both bird species’ numbers are
still declining, and the US Fish and Wildlife
Service is now considering whether to list
them as threatened, Whitbeck says.Still, it’s not at all clear how the changing
landscape is influencing local biodiversity
overall. For example, North Carolina–based
wildlife ecologist Paul Taillie, currently a
University of Florida postdoc, and colleagues
recently showed that while the transition
from wetland forest to ghost forest in North
Carolina detrimentally affected certain bird
species that need heavily canopied forests to
survive, it appeared to benefit a number of
bird species that live in dense shrubs.^6 Simi-
larly uncertain are the effects of ghost for-
ests on the landscape’s ecosystem services,
as demonstrated by Martinez’s work on the
corking of greenhouse gas emissions by dead
tree trunks.
To get scientists who are studying these
changes to talk with one another about
their findings, Bernhardt is spearheading
an effort to coordinate all of the research
on saltwater intrusion in landscapes from
the Gulf of Maine to the Gulf of Mexico.
She and nearly 80 other researchers have
started collaborating, using funds from the
Environmental Research Institute at the
University of Virginia, and the team has
applied for a grant from the National Sci-
ence Foundation to collate the “explosion
of research... documenting the dramatic
ecological change well inland as a result
of salinization of surface waters, soils and
ground water,” according to the proposal.The scientists, together with local com-
munities, want to help land managers
decide what to do with land that’s becom-
ing increasingly salty and therefore less use-
ful for farming, logging, and other human
uses. (See “Losing Land” on page 34.)
“Ghost forests will be a memory,” says
Matt Kirwan, an ecologist at the Virginia
Institute of Marine Science—only “a marker
for the next fifty to a hundred years of what
the land once was.” gReferences- M. Martinez, M.S. Ardón, “Greenhouse gas
emissions from standing dead trees along the
Albemarle Pamlico Peninsula, North Carolina,” AGU
Fall Meeting Abstracts, 2018. - C.L. Stagg et al., “Causal mechanisms of soil organic
matter decomposition: deconstructing salinity and
flooding impacts in coastal wetlands,” Ecology,
98:2003–18, 2017. - A.M. Helton et al., “Hydrologic context alters
greenhouse gas feedbacks of coastal wetland
salinization,” Ecosystems, 22:1108–25, 2019. - A. Bhattachan et al., “Evaluating the effects of
land-use change and future climate change on
vulnerability of coastal landscapes to saltwater
intrusion,” Elem Sci Anth, 6:62–73, 2018. - E. J. Meyers et al., “Blackwater 2100: A strategy for
salt marsh persistence in an era of climate change”
(Arlington, VA: The Conservation Fund, 2013). - P. J. Taillie et al., “Bird community shifts associated
with saltwater exposure in coastal forests at the
leading edge of rising sea level,” PLOS ONE,
14:e0216540, 2019.
LOST FOREST: A strip of dead trees runs along
the Catlett Islands in the York River, a few miles
north of Yorktown, Virginia. The trees have
succumbed to saltwater intrusion from both sides
and are now only a reminder of the forest that
once lived there.