The salt marsh at Audubon’s Shadblow
Preserve on the Narrow River in Narragansett is wetter than it should be at low
tide. Near the highest point on the marsh, Scott Ruhren stood nearly ankle deep
in water, and shallow tidepools were unable to drain naturally, providing
breeding habitat for mosquitoes. At the inland edge of the marsh, invasive
phragmites were encroaching in areas where salt hay – a native plant that
Ruhren said looks like the cowlick on a 10-year-old’s head – should be thriving
instead.
A few killdeer and Wilson’s snipe
called loudly when they flew off at the approach of Audubon’s senior director
of conservation, but little other bird life was noticeable in early spring,
other than a few soaring gulls. It was a bad sign.
“Just about every salt marsh in
Rhode Island is having problems like these,” said Ruhren
|
Rhode Island salt marsh (Jake Zach) |
of the 20-acre marsh
property donated to the Society in 1974. “Our most obvious issue here is
ponding of the water, rather than it draining, which is causing a switch-over
in the plant community and a die-off of plants that can’t survive being constantly
inundated.”
Nearly all of the significant problems
facing salt marshes in Rhode Island can be traced to rising sea levels – caused
by melting glaciers and the thermal expansion of warming waters – and
increasingly severe storms, both of which result in flooding and erosion of the
habitat that serves numerous ecological functions.
According
to Kenny Raposa, research coordinator at the Narragansett Bay NationalxEstuarine Research Reserve on Prudence Island, salt marshes are essential
habitat for numerous species of fish and birds, and they absorb large
quantities of carbon from the atmosphere. They also filter out pollutants and
protect shorelines and property from damage caused by storms and waves.
“Salt marshes require regular
flooding with tidal waters, but it’s a delicate balance,” he said. “If they’re
flooded too much, they drown and convert to open water. At high tide, essential
nutrients are brought in for the plants. Low tide gives the marsh soils some
time to dry out and provides access for birds and wildlife to use the marsh for
feeding.”
Raposa, who has been tracking the
decline of salt marshes in Rhode Island for close to 10 years, said that sea
level rise has led to the loss of almost 20 percent of the state’s salt marshes
in recent decades, and the rate is accelerating. His research has found that the salt marshes
in the region are the most vulnerable in the entire country.
“It’s happening right now, and it’s
happening faster than I thought it would,” he said. “At normal rates of sea
level rise, our marshes could keep pace as decaying plant matter and sediment
deposits helped the marsh grow vertically at the same rate as sea level rise.
But this just cannot happen fast enough anymore in our region, so the marshes
are essentially drowning in place.”
Salt marshes in the Northeast are
growing through this accumulation of plant matter and sediment at a rate of 1.4
millimeters per year, while sea level has been rising 5.6 millimeters per year
since 1999. It’s a trend that will only get worse. According to the National
Oceanic and Atmospheric Administration, sea level has already risen about 10 inches
in Rhode Island since 1930, and scientists predict it will raise two more feet
by 2050 and seven feet by 2100.
Raposa and Ruhren agree that the
ideal circumstances would allow salt marshes to migrate inland as the waters
rise. In some places that may be possible, though whether the marsh migration
can keep up with the rate of sea level rise is uncertain. But most salt marshes
in Rhode Island are faced with numerous barriers to their migration – roads and
other developments constructed behind the marshes prohibit their inland
movement, or the slope of the land limits how far they can move.
“Even worse,” said Raposa, “new
evidence shows that natural upland habitats like a forest can hold out longer
than we thought and prevent marshes from migrating.”
Other climate-related factors are
exacerbating the problem. Warming temperatures may accelerate the breakdown of
plant matter, making it more difficult for the marshes to grow in elevation to
keep pace with sea level rise. And warmer winter temperatures allow fiddler crabs,
which destabilize the soil with their burrows, to be active longer.
One of the biggest losers from the
flooding and loss of salt marsh habitat is the appropriately named salt marsh
sparrow. The only breeding bird found nowhere else but on the East Coast of the
United States, it is one of four local birds that breed exclusively in salt
marsh habitat. (The others are the seaside sparrow, clapper rail and willet.) Scientists
predict the sparrow will go extinct within the next 50 years.
Research by University of
Connecticut scientists Chris Elphick and Chris Fields has found that the
secretive streaked bird with a pale orange triangle on its cheek has been declining
by
|
Salt marsh sparrow at Jacob's Point, Warren (Evan Lipton) |
about 9 percent per year since the late 1990s.
“To put it in context, if your stock
portfolio was declining at that rate, you’d be losing money fast. It’s pretty
bad,” Elphick said. “About three-quarters of the population has disappeared.”
Steve Reinert, a part-time
ornithologist who has been studying salt marsh birds in Rhode Island since the
1980s, hasn’t observed a noticeable decline in the population of salt marsh
sparrows yet, but he knows it won’t be long before he does.
“Call me a pessimist, but I have
little hope for this species,” said Reinert, a member of Audubon’s Council of
Advisors. “It’s a species of global concern.”
The problem the birds face has
everything to do with the rising water levels in their breeding habitat.
Salt marsh sparrows build their
nests on the ground in areas of high marsh that typically do not get flooded
except at high tide on nights with a new moon, which occurs every 28 days. It
takes the birds that entire 28 days to build a nest, lay and incubate eggs, and
raise nestlings to the point when they are able to make their first flight.
Reinert
said that the birds’ first nesting attempt typically fails when it is flooded
during the first new moon tide of the breeding season. But as soon as that
happens, the birds start the process all over again and the nestlings typically
fledge on the day of the next moon tide. Sometimes the young birds have to
climb out of their nest and up an adjacent reed to avoid the rising tide on the
last day or two before they are able to fly.
“Most
of our successful nests get synchronized to the tidal cycle,” Reinert said.
“All of the birds lose their first nest on the same night, and they all start
building the new nest the same day.”
But
as sea levels are rising, the birds are finding it more and more difficult to
complete their nesting cycle before the high water returns.
“It’s
already incredibly close for them without adding sea level rise. It’s always
been touch and go,” said Reinert. “But now the whole balance of the equation is
being thrown off, and they can’t afford to lose a day. The combination of a
higher amplitude of tide and a potential shorter period to complete the nesting
cycle can dramatically throw off this balance of nature. That’s where the
devastation will come.”
“It doesn’t take too much sea level
rise to flip the switch for the birds,” added Elphick. “Literally, a couple
inches can make the difference.”
Unfortunately, little can be done to
protect the birds in the long term, since any steps taken now to reduce sea
level rise won’t have a practical effect until it’s too late. And while Elphick
is exploring potential short-term fixes – like identifying the marshes that are
least susceptible to the effects of sea level rise so they can be protected –
he, too is pessimistic that the birds will last much beyond mid-century.
While the outlook for the sparrow
appears bleak, there are still numerous strategies that can be employed to
preserve at least some of the salt marshes in the region. At the Sachuest Point
and John Chafee national wildlife refuges, for instance, sand is being trucked
in to raise the elevation of the marshes. Elsewhere, barriers to salt marsh
migration, like old roadways, parking lots and other infrastructure, are being
removed. And Kenny Raposa and others are experimentally testing the
effectiveness of other ways of helping marshes survive the onslaught, from
carefully digging channels into waterlogged sections of marshes to help them
drain to seeking ways to help marshes migrate more quickly into adjacent uplands.
But
deciding which marshes to protect and which to allow to disappear is difficult.
Meg Kerr, Audubon’s senior director
of policy, acknowledges that Rhode Island has a great deal to consider when
setting priorities for responding to climate change, especially when it comes
to sea level rise.
“Resources are not endless,” she
said. “So when it comes to salt marsh restoration projects, I’ve been making
the argument that we need to step back, take a good look at where the best
chances are for salt marshes to retreat and remain viable ecosystems, and make
sure we’re investing in and prioritizing those sites.”
She worries, however, that some in
the scientific and coastal management community are inclined to wait for a
better model or new evaluation tools before making these crucial decisions.
“The tools we have now are good
enough to tell us where the best options are for marsh migration,” she said.
“There are lots of important players, including Audubon, who are already
working together to implement salt marsh restoration projects, so let’s use the
tools we have and keep going.”
Using the national Sea Level Affecting Marshes Model, the Rhode Island Coastal Resources Management Council
has mapped every coastal community in the state to identify the low-lying
upland properties adjacent to salt marshes that may allow for future marsh
migration. While the maps suggest that 80 percent of the state’s salt marshes
will be lost from five feet of sea level rise – which would be expected to
occur by the 2080s – marshes in upper Narragansett Bay appear to be less
vulnerable than those along the south shore.
According to Caitlin Chaffee, the
CRMC policy analyst who manages the state’s Coastal and Estuarine Habitat Restoration Trust Fund, priority areas for salt marsh restoration will likely
be based on marsh size, migration potential, those in important bird areas, and
those containing rare sea level fen habitat. There are many potential
intervention actions that can be taken at priority marshes, but she told
attendees at the Rhode Island Land and Water Summit in March that “the fact
that we’re already putting sediment on our marshes is an indication of how dire
a situation we have. At first thought you’d think that marsh filling would be a
serious no-no, but now we’re saying it’s a good thing.”
While some scientists and coastal
advocates are trying to put a positive spin on prospects for preserving salt
marshes for the long-term, most appear to recognize that they are fighting a
losing battle. Kenny Raposa, for one, finds hope from the many dedicated people,
like Kerr, who are working together to try to figure out what can be done to
preserve as many marshes as possible. But he also admits that he’s “quite
pessimistic. I’m literally seeing and recording the loss of these marshes every
year,” he said.
Steve Reinert feels a similar
sadness for what is being lost.
“As a salt marsh researcher for 46
years in Rhode Island and southeastern Massachusetts, the thought of losing one
of my favorite places, my favorite environments to walk and take people to and
birdwatch in, is personally devastating,” he concluded. “I love the smell of
the salt marsh, the prospect of a clapper rail running in front of you, fiddler
crabs nipping at your toes. To think that the marsh may not even be there to
walk any more is very depressing.”
This article
first appeared in the June issue of Audubon Report, the newsletter of the Audubon Society of Rhode Island.