Article body copy
The land beneath Chesapeake Bay, the largest estuary in the United States, is sinking. Couple that with climate change, and the sea level is rising twice as fast as the global average, chewing away at shorelines and drowning islands. Private landowners, who occupy about 85 percent of the shoreline, have responded with walls, rocks, and barriers, which have helped slow the losses. But evidence is growing that this coastal hardening may be insufficient at holding back future seas, and is doing serious damage to more than a dozen fish and crustacean species. Now, planners and landowners are hoping engineered living shorelines can solve both problems at once.
A hardened shore makes life more difficult for trout, perch, crab, and other species that need a natural shoreline to thrive, says Matthew Kornis, who recently published a paper evaluating the effect of shoreline hardening on these species.
Kornis, a fish biologist with the US Fish and Wildlife Service, studied hundreds of sites in and around Chesapeake Bay, from natural beaches and marshlands, to shores lined with riprap (cages of loose rock) and bulkheads (walls, often wooden). The harder the shoreline, he found, the harder hit the species. This was true even for riprap, which is often considered more environmentally friendly than sheer walls.
Kornis says natural shorelines offer things hardened shorelines don’t: juvenile fish live in the nooks and crannies of wetland shorelines, for instance, and these environments serve as nurseries. Fish also feed within beds of seaweed and seagrass. Hardening decimates these complex habitats, leaving nothing to eat and nowhere to hide.
Hardening isn’t unique to Chesapeake Bay. Estimates suggest that about 14 percent of the United States’ coast had been hardened, and the shorelines of Europe and China are also heavily armored. While the motivations for reinforcement vary (development, industry, sea level rise), most Chesapeake Bay residents are trying to protect their property from rampant erosion. Sea level rise is a relatively new problem for many coasts, but land subsidence means it’s been the norm in the Chesapeake for a long time.
“Erosion has been happening for centuries,” says Zoe Johnson, climate change coordinator with the US National Oceanic and Atmospheric Administration in Chesapeake Bay. Tide gauge data shows the water rose nearly a third of a meter in the past century. Similarly, the sea moved inland by roughly half a meter a year on average. But these rates are accelerating as climate change adds a rising sea to sinking land. “The influence of global factors will outpace the land subsidence,” she says.
In the early 2000s, Maryland convened a climate change task force, including Johnson, to study how to better adapt to these future seas. They identified one promising method that seemed to stand up to the sea: living shorelines.
Designs vary widely, but most living shorelines start with a barrier, such as a rock wall, oyster reef, or log, placed several meters out in the water. The barrier is then backfilled with plants and soil to make a marshy buffer zone. In 2008, Maryland passed the Living Shorelines Protection Act, which Johnson says requires owners to prove that a living shoreline will not work in their location before they can get a permit to construct a wall.
Along with erosion control, living shorelines have other benefits. Researchers in North Carolina showed that living shorelines can act as nurseries for fish and crustaceans, the way natural shorelines do.
Bhaskar Subramanian, the shoreline conservation section chief for the Maryland Department of Natural Resources, says his job now is to teach people about living shorelines, which he speaks of with infectious zeal. He sets up information sessions for planners and residents, talks to marine contractors and engineers about how to build living shorelines, and consults with homeowners about what would work on their properties.
Subramanian says there’s skepticism by some landowners, who think only a wall can hold back the waves. But enthusiasm for living shorelines is growing, he says, noting that 2003’s Hurricane Isabel was a turning point. After the storm, Subramanian got a lot of calls from the neighbors of those with living shorelines, who all said pretty much the same thing: “I had a bulkhead, now it’s somewhere in the bay. And my neighbor, who has your living shoreline project, he still has a shoreline.” Many people wanted to upgrade, Subramanian says.
In his consultations with landowners, Subramanian is careful to work with their goals. If they want a beach or a dock, he tries to incorporate that into the design. And he keeps as close as possible to the original coast. “If there was a beach from time immemorial, I would not want to convert that to a marsh. Nature is telling me she prefers a beach there,” he says.
Subramanian admits that living shorelines cost more than walls, because there are more materials and structures to consider. It also takes a lot longer to get a permit for a living shoreline, despite some streamlining in the process. But Maryland has implemented a cost-sharing loan program. And he thinks the upgraded shores are starting to speak for themselves.
Kornis, too, is enthusiastic about living shorelines, though he thinks the science on their ecological effectiveness still needs some strengthening of its own.
Adapting to climate change is a steep challenge. Kornis’s research on the effect of shoreline hardening on marine ecosystems underscores how part of being a coastal landowner is taking responsibility for that adaptation.
“People that live directly on the coast, they tend to really care about the system that they’re living on,” he says. “Folks are willing to listen when it comes to issues like this. And you know, this is really a situation where you string together individual decisions, and it really can make a difference.”