The Best Defense Against Sea Level Rise Leaves Little Room for Birds
The seawalls that fortify our coasts against rising seas also degrade bird habitat. But there are few good solutions unless people retreat inland.
Karl Nordstrom has grown used to seeing a world invisible to everyone else. When he goes to the Jersey Shore and gazes upon an endless stretch of white sand, he doesnt see the pinnacle of natural beauty like most beachgoers. Rather, he sees a human inventiona recreation platform, as he calls the raked white beaches at coastal resorts and summertime shore towns.
If youre looking at the beach every summerif you go out there, and its practically graded flat, and theres no vegetation on ityou begin to think thats what the beach is supposed to look like, he says. If the beach always looks the same, you lose sight of the fact that its dynamic. The whole thing is dynamic.
A coastal geologist at the Rutgers School of Environmental and Biological Sciences, for 40 years Nordstroms studied the natural evolution of beacheshow waves erode and reform beaches on daily and seasonal cycles, and how those natural cycles create hill-like dunes that support wildlife and protect inland areas from storms and flooding.
For decades coastal towns have called upon his expertise as they prepare for and . Rising seas related to climate change are eroding beaches and pushing inland, endangering homes and property that were once considered safe. But people rarely take Nordstroms advice, which is to abandon their homes and retreat from the coast. If you can see the sea, the sea can see you, and youre at great risk, he says.
Instead of moving, homeowners and communities are resorting to coastal protection plans that offer an appearance of safety but no guarantee. Some towns are trucking in sand to replenish eroded beaches and build artificial dunes. But more often than not, people are building seawalls in front of their homes and behind beaches. Often 20 feet tall or higher, these concrete behemoths are constructed to withstand the sustained assault of incoming waves and storm surges. Seawalls , or nearly 15,000 miles, of the United States coastlinea number thats expected to grow in the coming decades as the sea level rises.
As construction intensifies, a growing chorus of scientists and environmentalists are raising concerns over an unintended consequence: Seawalls eliminate habitat for birds and other wildlife. Their footprints take up space on the beach the day they're built. Then, over the course of decades, when natural cycles of erosion and sand deposition are disrupted.
Even before seawalls fully erode beaches, they drive wildlife from the area, according to a study . The analysis pooled data from 25 studies about seawalls, and found that half as many organisms and a quarter fewer species live on beaches and marshes in front of seawalls compared to seawall-free areas.
No group of animals reacted more strongly than birds. In , Jenny Dugan, a coastal ecologist with the University of Californias , counted more than 6,800 birds along three miles of Santa Barbaras beaches over the course of a year. The beaches were identical except that some had seawalls and others didnt.
On the beaches in front of seawalls, she saw one-third as many shorebirds and one-quarter as many gulls and cormorantsan undeniable trend. It was completely different for the birds between armored and unarmored [beaches], Dugan says. It was a very clear signal for us.
Birds avoid seawalls for a simple reason: They need dry sand, which is often lacking on the eroded beaches in front of seawalls. In her study, nearly every beach in front of the 80-year-old seawalls lacked dry sand. Without that dry sand zone, birds dont have refuge from the waves as they forage in the surf. They also lose an important food source. Dugan found 15 times as many tiny invertebratesshorebird foodon beaches without seawalls.
Once you lose that [dry sand zone], you lose all that biodiversity, Dugan says. Thats the food thats available to birds during high tides. Its a big part of the food web."
What makes this loss of habitat even more unsettling for researchers is that it might not be necessary. The effectiveness and practicality of seawalls is often debated. In some cases, they have , but in others, they have . Seawalls also require constant upkeep; with each wave, the concrete slowly weakens and crumbles. And as sea level rises, what was once a tall-enough wall may not provide enough protection.
Seawalls will not last forever," Nordstrom says. "Theyre considered a permanent solution, but theyre not. They are the last-ditch defense if theres nothing else you can do.
In Nordstroms ideal world, people would retreat from the coasts, leaving the beach to serve as a buffer zone to protect inland areas and as habitat for birds and other wildlife. Thats definitely better than a seawall, he says. After decades of pleading, though, hes had to accept that coastal retreat isnt going to happen any time soon.
To make the best of a bad situation, Nordstrom now advises coastal homeowners to combine defensive seawalls with habitat restoration. If you must have a wall, put that wall as close to human infrastructure as you can and let nature be in front of it, he says. And piling sand on top of a seawall can create a reinforced dune while providing habitat for wildlife. Nordstrom also encourages people to plant native dunegrasses and shrubs on their lawns as well as on beachfront sand. If they take his advice, before long those raked white beaches may well look more like the dynamic natural habitats they are meant to be.
Appreciate the coast for more than just sand and sun and blue water; appreciate it for the way it evolves and grows, and is eliminated and comes back, Nordstrom says. Thats part of the cycle of nature. Texture, typographic diversity, changeembrace it.