MATT KIRWANsurrounds the land can be pushed upstream
by the wind. In drought conditions, lots of
water evaporates, leaving behind saltier
water to get blown inland. “When we have
these long, extended, two- or three- or four-
month droughts like we did in 2007 and
2008, we saw the water getting saltier and
saltier and saltier,” Bernhardt says. And
when it did rain, the salt didn’t go aw ay. The
soil was still caked in salt when it dried out
after the rain.
Land managers at Goose Creek State
Park, which sits on the southern side of
the Albemarle-Pamlico Peninsula, ran
into a similar problem in 2011 as Hur-
ricane Irene blasted the coast, creating
a storm surge that pushed tons of salty
water into the sounds and rivers, flooding
coastal towns. After the waters receded,
the land managers noticed that the water
at Goose Creek was still salty. The cause in
this case—identified by NC State hydrolo-
gist Ryan Emanuel—was a raised dirt road
that cut across the forest and prevented
drainage of a pool of salty water that had
formed in the forest during the hurricane.
“I got interested in ghost forests through
this very specific problem that was happen-
ing at Goose Creek State Park,” Emanuel
says. “And then, as I drove around eastern
North Carolina, I became attuned to just
how widespread [the problem] was.” And
the saltwater wasn’t just affecting forests,
but farms, too.
When Emanuel chatted with Ardón,
Bernhardt, and other researchers in North
Carolina about what he’d seen, they all
agreed that saltwater intrusion would
become a major issue all along the North
Carolina coast. Once inland, salt begins to
blight farmland and to damage trees, creat-
ing the now-iconic ghost forests. With both
droughts and storms expected to worsen
and increase in frequency as Earth’s climate
warms, the researchers hope to understand
exactly how salt kills and to identify early
signs of salt stress that could flag at-risk trees
and crops before they become ghosts.
“What we’d love to know is which for-
ests are vulnerable, which forests are likelyto become ghost forests in the near future,”
says Bernhardt. “That might help us actu-
ally think about how to manage the [for-
ests], and perhaps protect them.”A series of salty experiments
With this goal in mind, Bernhardt, Ardón,
and their collaborators decided to run an
extreme experiment: carefully sprinkle large
bags of aquarium salt into plots in the
restored wetland forest at Timberlake. The
team also used similar tactics in the green-
house on Duke’s main campus in Durham.
Added salt makes it harder for plants to take
up water because excess sodium and chloride
ions accumulate around the roots, keeping
the water in the soil instead of letting it dif-
fuse into the roots. In addition, the sodium
and chloride ions that do move into plants
damage their tissues and prevent the pro-
duction of chlorophyll, the light-harvesting
pigment essential for photosynthesis. Ulti-
mately too much salt will kill the plants.
As the researchers watch the plants
respond to the added salt, they are look-
ing for changes in spectral traits—the light
reflected from the plants—and other char-
acteristics that could reveal that they are ill
well before they are on the verge of death.
“We really would like to be able to sense salt-
related stress from [satellites in] space or
from drones,” Bernhardt says, “but we don’t
know what that looks like yet.”
Part of the reason the researchers want
to protect the trees is because they take in
greenhouse gases, such as carbon dioxide
(CO 2 ), and sequester carbon in their tissues
and in the soil. But if forests die en masse, it’s
not clear what happens to those greenhouse
gases. To figure that out, Melinda Martinez is
“measuring tree farts,” as Ardón likes to say of
his student’s work. Specifically, Martinez usesBlackwater is really a place where people can see the
impacts of sea level rise with their own eyes.
—Matt Whitbeck, US Fish and Wildlife ServiceTREE GRAVEMARKERS:The skeletal remains
of a forest rise out of the marshy grasses near the
Blackwater River in Robbins, Maryland.