Rather than armoring our coastlines, we should help people and shorebirds alike by turning to living shorelines to strengthen resilience to sea-level rise and extreme weather events.
By: James Lowen
Setting his throne on the seashore, Canute the Great commanded the incoming tide to halt. He knew it would not. The 11th-century King of England, Denmark and Norway – whose name is today carried by Red Knot (Calidris canutus) – was illustrating the limits of human power when faced with the mighty elements. Let all men see, he reportedly beseeched, how empty and worthless is the power of kings. A millennium later, as people and wildlife living along coastlines are swamped by rising seas and battered by intense storms, Canute’s words ring ever truer. Hearteningly, however, there are signs that we are finally understanding that working with nature, rather than against it, can strengthen coastal resilience.
This century, according to the United States’s National Oceanic and Atmospheric Administration (NOAA), tidal flooding has surged by an average 233% across the United States (US). Worse will come: NOAA envisages sea levels rising as much over the next 20 years as during the past 60. Because coastlines are so important for human communities, their heightening susceptibility to flooding, erosion and sedimentation levies eye-watering costs. Since 1980, NOAA calculates that the overall cost and damage of 308 US weather and climate disasters have exceeded $2.3 trillion. During the 1980s, there were three events on average per year, costing $19 billion. From 2016–2020, those annual averages leapt to 16 disasters costing $128 billion. This raising cost of climate disasters has driven US states and cities to invest billions in coastal protection plans.
Tidal flooding has surged by an average 233% across the United States, with sea levels rising as much over the next 20 years as during the past 60.
Elsewhere, stakes may be even higher. According to the Inter-American Development Bank, most people in Latin America and the Caribbean inhabit coastal areas. On Punta Soldado Island, in Colombia, Johann K. Delgado with the Cornell Lab of Ornithology explains that “the coast has retreated 600m since the 1980s, particularly following major El Niño events, forcing local communities to relocate at least three times.” Matters will worsen: by 2100, Johann says, “once-a-decade flooding incidents could become monthly.”
It’s not just human communities that will lose their homes; shorebirds will too. Sea-level rise on Punta Soldado, Johann says, “has already modified habitats used by thousands of shorebirds”. One study suggested that global sea-level rise of 34cm by 2100 – lower than some scenarios – could remove 70 percent of the intertidal feeding habitat of southern San Francisco Bay (USA), a Western Hemisphere Shorebird Reserve Network (WHSRN) Site. This is then combined with infrastructural development which has shrunk coastal landscapes and the coastal defense that prevents the migration and re-formation of natural habitats. Shorebirds are being squeezed.
Global sea-level rise of 34cm by 2100 could remove 70 percent of the intertidal feeding habitat of southern San Francisco Bay (USA).
For decades, curbing the sea’s wrath has typically involved building ‘hard’ or ‘grey’ structures to keep water out – armoring shorelines with seawalls, groins and bulkheads. There is increased understanding that abrupt boundaries between land and water may make things worse – exacerbating vulnerability by interrupting critical environmental processes, while depriving wildlife of living space.
Alternatives to hardening coastlines constitute a flexible, varied toolkit. Planning policies can limit coastal development, for example. The Inter-American Development Bank considers that “coastal setbacks offer considerable potential”. Implemented in Canada, Costa Rica and Barbados, a setback policy prohibits development within a specified distance of the sea, allowing room for rising seas to move the high-water mark inland.
Conservation easements – legally binding agreements prohibiting specified developments even if ownership changes – also help. In the Maryland–Virginia Barrier Islands WHSRN Site (USA), The Nature Conservancy (TNC) manages 70 easements at its Volgenau Virginia Coastal Reserve (VVCR). Combined with the extensive lands TNC and others own, some 5,260 hectares of private conservation easements “contribute significantly to the overall resiliency of this landscape” while “protecting marshes and mudflats that are important for shorebirds,” TNC’s Alexandra Wilke says.
Hard infrastructure or ‘rip rap’ is used to protect a road separates salt marsh from sandy beaches, preventing natural migration. Photo: Laura Chamberlin
Land purchase has also been key at Delaware Bay (USA), a WHSRN Site that is internationally important for migratory shorebirds including Red Knot. Here a 2.5 centimeter rise in tidal levels can temporarily extend water 300 metres inland. Delaware state authorities, The Conservation Fund and partners now own much of Mispillion Harbor on the Bay’s shores, seeking to prevent potentially harmful coastal development. The State of Delaware has also invested $8 million to restore shorelines after damage by coastal storms such as 2012’s Hurricane Sandy. In 2018, Senator Tom Carper emphasised that “the money was put to good use. We didn’t just fix the damage, we created a long-term plan to mitigate damage from future storms.”
Constraining the location of new construction is one thing, but what can you do when existing development is routinely imperilled by increasing coastal storms – even before sea-level rise floods in? One option involves moving people away from susceptible areas – by buying them out. In 2019, Associated Press computed that US authorities had spent $5 billion across three decades to purchase tens of thousands of flood-prone homes.
With 2,900 kilometers of tidal coastline and 80,000 hectares of tidal wetlands, New Jersey’s communities are notably vulnerable (USA). From 2013 to early 2021, the state’s ‘Blue Acres’ program struck agreements with 827 homeowners across twenty municipalities. State authorities have pledged to expand Blue Acres, offering flood-prone homeowners buyouts where engineering solutions are impractical or too expensive. This makes sense: the Union of Concerned Scientists projects that 62,000 New Jersey homes risk chronic flooding by 2050. Wildlife habitat will suffer too: in the state’s Climate Change Resilience Strategy, officials admit that sea-level rise of 30–60 centimeter by 2050 could destroy 28 percent of tidal salt marshes. “To engineer our way out of this in all areas is not a worthwhile thought,” New Jersey’s David Rosenblatt argued at the Strategy launch.
Nature-based shoreline stabilization that incorporates vegetation or other living elements increases coastal resilience and provides wildlife habitat while allowing for natural migration of marshes. Hard infrastructure cuts of the natural interaction of land and water, limiting wildlife habitat and flood management benefits of marshes. Graphic created by Vi Ramirez, Manomet.
Such sentiments haven’t stopped people thinking differently about coastal engineering. On the west side of Delaware Bay, one innovative solution is driven by the loss of impoundments (coastal waterbodies), which were damaged when the sea breached barrier dunes. In response, the State of Delaware is constructing two new impoundments to create a 34-hectare wetland at the Ted Harvey Wildlife Area. Shifting coastal habitats inland and ‘uphill’ provides climate-smart roosting and feeding habitat for shorebirds alongside benefits to people. Another impoundment will be allowed to convert partially to saltmarsh, thereby buffering impacts of surging seas.
Treating saltmarsh as a tool illustrates that ‘living shorelines’ – nature-based shoreline stabilization that incorporates vegetation or other living elements – can strengthen coastal resilience. According to NOAA, living shorelines “maintain continuity of the natural land–water interface and reduce erosion while providing habitat value and enhancing coastal resilience”.
This approach is being widely adopted. At Aramburu Island (California, USA), conservationists rejected traditional hard methods of ‘protecting’ shorelines in favour of soft engineering methods that dissipate (rather than reflect) wave energy. Eucalyptus-log micro-groins and low-angle shorelines reduced erosion, while woody debris provided habitat structure and perches. Within a year, thousands of shorebirds, including Black-bellied Plover (Pluvialis squatarola) and Black Oystercatcher (Haematopus bachmani), were enjoying enhanced tidal mudflats and marshes. For Julia Kelly and Danielle Montijo of the National Audubon Society, “the modifications are expected to allow the island habitats to adapt to forecasted sea level rise”.
Wood is also being used at Colombia’s Punta Soldado. Johann hopes that a “pilot wooden barrier will protect coastal vegetation and enhance sedimentation, recovering key areas for shorebirds and the community”. In Suriname, mangroves offer a solution. At Weg Naar Zee, part of a WHSRN Site, coastal erosion and mangrove-felling removed soft mud favoured by shorebirds such as Lesser Yellowlegs (Tringa flavipes), whose local population entered freefall. “Installing sediment-trapping structures and planting mangroves,” Manomet’s Arne Lesterhuis says, “helped reverse erosion – benefitting shorebirds and stabilizing the coast.”
Left: A man-made oyster reef replaces long-gone natural oyster reefs, providing habitat for wildlife and slowing erosion with wave attenuation and sediment trapping. Photo: Damon Noe, The Nature Conservancy. Right: Sediment-trapping structures with mangrove plantings at the Bigi Pan WHSRN sit are used to slow erosion and stabilize the coast. Photo: Arne Lesterhuis.
At VVCR, TNC “has been restoring oyster reefs for decades, but only recently has this been “recognized and prioritized as an important strategy for local communities to adapt to climate change” says Alex. TNC is communities and habitat”. As Alex highlighted, VVCR can serve as a model for how conservation can help both human and natural communities adapt and become more resilient”.
Rising sea-levels and extreme weather events create an unexpected alliance of need: coastal resilience for communities and shorebirds. Even though the driving factor of this climate change is human, nature will provide the solutions. From planners and politicians, engineers to ecologists, people are increasingly understanding that a hard and fast separation of land from water provides no long-term solution and coastal ecosystems can offer defense against inundation. Investing in nature-based solutions embraces the limits of human power that King Canute recognized those many years ago.
Cover Photo: Barrier islands (without infrastructure) are an important part of a dynamic and resilient shoreline with the sand and marshes shifting under the power of the waves, protecting the uplands. Photo: Zac Poulton
