Sable Island seeing loss of fresh water as storms and erosion increase

Researchers at Dalhousie University have discovered a decrease in freshwater on Sable Island that is likely connected to climate change and is a warning about the danger facing small islands around the world.

Julia Cantelon, a PhD candidate in Dalhousie’s coastal hydrology lab, led the study. It was co-authored by Barret Kurylyk, the Canada research chair in coastal hydrology at the Halifax university.

Published in Water Resources Research. Cantelon’s research suggests that while saltwater that gets inland because of storms and erosion can be flushed out by rainfall, there often isn’t enough time for the fresh water to recover before another storm hits.

Cantelon and Kurylyk collected groundwater data from 2019 to 2022 and compared its salinity and distribution to the last data collected in the 1970s. They found that decades of dune erosion, seasonal waves, storms and hurricanes had reduced the amount of fresh water on the island.

The water supports the island’s wild horses, along with plant and insect life.

Cantelon said the research shows that where dunes have remained intact, there was no difference in fresh groundwater, but in other areas there is less.

“The areas that are experiencing a decline are found along the coast and are tied to the dune topography or the erosion of those dune barriers,” she said. “What we found is that when storms batter the coast and cause the loss of the coastal dune… that is closest to the ocean, we lose the fresh groundwater under that.”

Cantelon said there has been a loss of the dune on the south part of the island, and they found an associated loss of fresh groundwater under the dune.

The water in the middle of the island, where the dunes are still healthy and where ponds that the horses usually drink from are found, is still in good condition and the same as in the 1970s. But, Kurylyk said, because the horses are known to dig down half a metre to a metre to the water table to drink groundwater, the findings mean that they may not be able to get that water in as many places as they’re used to drinking.

“I think the main takeaway from my work is that the changes you see to the surface of Sable Island are driving sub-surface changes,” Cantelon said. “Our findings are really useful for Parks Canada because they could track surface changes in the dune topography and get a sense of how the water resources might be changing.”

Kurylyk said 10 per cent of the world’s population lives on islands, “and those islands are changing in response to sea level rise and intensifying coastal storms, so our work on Sable Island is transferable to a lot of more populated barrier islands, like the sandy islands you see along the eastern coast of the U.S. and places where you see a lot of people.”

He said sandy barrier islands rely on groundwater for drinking supplies and other water needs, so “the loss of freshwater due to erosion could have profound societal implications.”

While places like the United States may be able to come up with solutions because of financial resources, that’s not the case everywhere.

“There’s a classification of countries called small island developing states, and a lot of them have lower socio-economic status and a lot of them are fairly remote … so to get fresh water out to them would be really challenging,” Kurylyk said.

Raises alarm bells

The study raises alarm bells about the ongoing and growing impacts of climate change.

“In a changing climate where you can expect higher sea levels and more frequent and more intense storms, you could see more frequent flooding of those low-elevation beaches, more erosion and more fresh groundwater loss,” Cantelon said.

She said she didn’t look at the trends and frequency of storms on Sable Island to be able to speak to whether the patterns are directly tied to climate change. “But what we are seeing is with more storms, there is more salinization of the beach and more incremental erosion and more fresh groundwater loss.”

Kurylyk said trying to mitigate the effects in the short term could involve construction of seawalls or breakwaters, or nature-based solutions like having coastal transition zones that can dissipate wave energy and absorb some coastal flooding, or moving dykes.

Cantlon said the findings could also be used to guide future development and planning so people are building homes or wells a safe distance back from the coast because oferosion and flooding potential.