Breaching tradition: Salt marshes replacing Nova Scotia's dikes

Dikes were first deployed by Acadian settlers in the 17th century to transform tidal wetlands in the Bay of Fundy into agricultural fields. Their efforts created some of the most fertile farmland in the Maritimes. Over time, important infrastructure such as roads, rail links and entire communities took advantage of the protection offered by dikes.

With climate change, sea levels are rising faster than dikes can be topped up. That challenge is compounded by the fact dikes are also subsiding.

As researchers, government officials and citizens look at new ways to protect Nova Scotia's coastal communities, one marsh near the border between Nova Scotia and New Brunswick represents the new reality on a coastline that hasn't changed for hundreds of years.

The roughly 15-hectare patch of marsh along the Missaguash River in Fort Lawrence, N.S., used to be farmland. Now, it's one of two pilot sites for a new method of coastal protection. Here, rather than building the dike higher to keep the sea at bay, researchers are letting the water flow through.

"These were areas that were previously identified as areas at high risk and high vulnerability," said Danika Van Proosdij, one of the lead researchers on a project called Making Room for Wetlands.

"And the cost of maintaining a dike in these places was prohibitive, but also was not possible ... because the trajectory of erosion was increasing."

The Making Room for Wetlands project is financed by the Department of Fisheries and Ocean's Coastal Restoration Fund. Researchers call the approach managed realignment. Dikes are breached and moved inland to restore tidal flow, allowing the salt marsh to spread out to the coast.

Salt marshes form a valuable line of defence against sea level rise and storm surges. But over the last 400 years, roughly 80 per cent of the salt marshes in the Upper Bay of Fundy have been cut off by Acadian dikes and more modern barriers including roads and causeways.

At the Converse Marsh site in Fort Lawrence and at another on the Cornwallis River, researchers are bringing some of those marshes back.

"We're actually leveraging the capacity of a coastal system to self-engineer and to provide the protective functions that we need to respond to climate change," said Van Proosdij.

Restored marshes also sequester carbon and provide valuable habitat for organisms ranging from plant life to fish and birds. But the marshes require people, at least in some cases, to reimagine the future.

Dairy farmer Doug Bacon of Upper Nappan, N.S., said the current way of managing the land has produced fields of irreplaceable value.

"That soil already has nutrients in it, all you need to do is to crown it, let the water run off and [that soil] will grow crops for my lifetime and anybody else's lifetime," he said.

Having looked at the Converse Marsh site, Bacon isn't sure about the change.

"It really is just a mudflat ... I'm really not convinced ... we need to look at it another way," he said.

'We can adapt to climate change,' says researcher

Van ProosdIj said asking people to accept a different kind of landscape has made the managed realignment projects complex.

"The idea of giving up the land ... or not holding the line or defending it, that is something that is challenging," said Van Proosdij.

"But I think it's all about reimagining. It's about people recognizing that we can adapt to climate change, but we're going to have to make some difficult decisions about where we live on the coast, how we interact with that coast, in order for us to have that viable future."

While researchers aren't suggesting managed realignment as the answer to sea level rise for every dike, Van Proosdij hopes that the Converse Marsh site will serve as a viable option when holding the line is no longer possible.

A hundred kilometres away, on a different part of the Bay of Fundy, the conversation about holding the line is taking a different turn. Since 1870, Advocate Harbour has been protected by a dike originally built by Acadian settlers. But that dike, and the natural sea wall located just beyond it, are under increasing threat due to climate change.

"I guess the sum of the facts about the dike is this: climate change is causing sea level rise. The dike is a fixed height," said Cumberland County emergency measures co-ordinator Mike Johnson.

A recent engineering study showed the dike is in good shape, but water levels are reaching the top more often, posing concerns for the future.

"Right now, our biggest concern is sea level rise and the fact that parts of the community that the dike protects are actually two metres below sea level at high tide, which is a pretty stark figure when you think about it."

For now, officials are planning to draw on approximately $3 million in provincial and federal funding to increase the dike's height by one metre. That fix should protect the community until 2030. Johnson hopes other solutions may emerge in that time.

"I wouldn't be surprised if they come up with even better ideas than what we have today," he said. "There's at least time now to consider those options."

Without new solutions, there are difficult conversations ahead for Advocate Harbour as its small population shrinks.

"At some point in time in the future, their population is going to be so little that it's going to be so much less expensive to move the community than it is to build a dike," said Johnson.

But the possibility of relocating parts of the community that are most at risk has not been easy for people to hear.

'Plan for the future and see what happens'

Mike Berry, the owner of the Advocate Country Store RiteStop, worries that without continued investment in the dike, the appeal of the community itself could be at risk.

"We all know the sea levels are rising. Why would I invest half a million dollars in a project in Advocate if I knew in 10 years time there's going to be water issues and nobody is going to help me?" said Berry.

"People want to come and live this lifestyle ... but we have to support it. Don't plan to pull the plug. Plan for the future and see what happens."

Kate Sherren, a professor at Dalhousie University's School for Resource and Environmental Studies, said conversations around climate change adaptations are difficult when they're happening at the level of individual communities.

"We have to start thinking about our collective challenge, and less about my home or my community versus all the others," she said.

Sherren's own research highlights the benefit of encouraging people to think about climate change as a collective challenge. When she led focus groups around the province and participants were asked to think about adaptations in the context of future generations on the scale of wartime mobilization, they were much more open to change.

"And so I think these conversations need to be put in a larger frame than they are right now ... because it is going to be a shared burden," Sherren said. "We all have to consider that making room for sea level rise includes making room for one another in this."

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