Fences in the Sand
How wild horses influence the dune ecosystems of Sable Island National Park Reserve
By Parks Canada
2024
This is Sable Island
Perched on the edge of the Continental Shelf in the Atlantic Ocean, Sable Island is a unique crescent-shaped island. It's a vegetated, shifting sand bar that stretches about 42 km long and is 1.3 km at its widest point.
Wild horses grazing on dune grass, Sable Island National Park Reserve (2020-11-01) by Adam CornickParks Canada
Wild horses
Sable Island is well known for its wild horses. These animals are among the few remaining unmanaged populations of wild horses in the world.
Sable Island horses are a naturalized species. They were brought to the island in the 1700s and over the years they have adapted to life on the ever-changing dunes.
Wild horses on a dune at sunset, Sable Island National Park Reserve (1905-07-14) by Gary BrintonParks Canada
Species can adapt to environments, but environments can also adapt to the species living in them.
On Sable Island, the horses modify the land by grazing on plants, creating trails on dunes, and spreading nutrients across the island.
A collaborative study
Parks Canada, in partnership with the Sable Island Institute, set out to better understand the relationship between the horses and the island.
The Fences in the Sand study takes a closer look at the role of wild horses in the dune ecosystems of Sable Island National Park Reserve.
Study objectives
Over time, this study will help us better understand how the wild horses of Sable Island influence:
• the evolution of dunes
• life in freshwater ponds
• rare species and their habitats
Study method
Exclosures are a common restoration tool. They effectively illustrate the ecological role of grazing animals.
Exclosures are designed to keep animals out of an area, unlike enclosures, which keep animals in.
A team of volunteers spent several weeks on the island building eight fenced exclosures, varying in size from less than half a hectare to over five hectares.
An example of a Sable Island exclosure
Use your mouse or finger to look around.
Horses next to an eroding sand dune, Sable Island National Park Reserve (2023) by Sarah MedillParks Canada
How do horses influence the evolution of dunes?
Horse paths and the transition from sand to vegetation, Sable Island National Park Reserve (2019-12-09) by Drew DoggettParks Canada
Horse paths
Horses modify their environment simply by travelling to find food, water, and shelter. As a result, there are horse paths all across Sable Island.
Areas of instability
Horses travelling up and down dune slopes create paths that can make the dunes unstable. The unstable dunes are more vulnerable to wind erosion.
Blowouts
Over time, wind erosion picks away at unstable dune edges. The eroded areas can grow into blowouts: openings in the dune edge that allow sand to move inland.
Blowouts are a natural part of dune evolution. They can often heal and regenerate into an intact dune.
However, horse activity can create blowouts in areas where they may not have formed otherwise.
Using drones to study dunes
Researchers use drones to take pictures of the study areas. The photos are combined to create 3D images.
These images let us map horse paths and see how sand is eroding or accumulating in areas with and without grazing.
Drones as research tools
Cross section of a freshwater pond, Sable Island National Park Reserve (1905-07-15) by Sydney SmithParks Canada
How do the horses influence life in freshwater ponds?
Horses at a freshwater pond
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Species at risk
Sable Island is home to a variety of rare and ecologically important species, including several species at risk.
Some of the Species at Risk found on Sable Island: Ipswich Sparrow, Sable island Sweat Bee, Roseate Tern
Rare species
In addition to Species at Risk, several rare moth and beetle species are found on Sable Island, such as the Ephalus latimanus darkling beetle.
Many of the rare species on Sable Island are nocturnal, so researchers carry out some of their work in the dark.
Working at night brings a whole new perspective to field work!
Here, a light trap is used to catch nocturnal moths.
Rare species, like all species on Sable Island, depend upon the habitat provided by dunes and vegetation. Preserving their habitat is a key way to ensure their continued survival.
Horses and rare species
What are the links between the horses and these rare and ecologically important species? Horses may be changing the habitat of these species by grazing, trampling, and redistributing nutrients across the island.
Horse eating marram grass, Sable Island National Park Reserve (2020-11-01) by Adam CornickParks Canada
Horses and habitats
Researchers and volunteers, Sable Island National Park ReserveParks Canada
Research partners
A large part of the work is carried out by our partner organization, the Sable Island Institute, and a team of researchers from Saint Mary's University, Dalhousie University, the Canadian Wildlife Service, the Geological Survey of Canada, and the University of Saskatchewan.
A look ahead
At the end of this study, Parks Canada, the Sable Island Institute, and research partners will better understand how the wild horses fit into — and influence — the ecosystem of Sable Island.
Understanding the horses' role in Sable Island's ecosystem will help Parks Canada protect the ecological integrity of this special place, as outlined in the park's management plan.
The Fences in the Sand project is part of the Parks Canada Conservation and Restoration (CoRe) program.
Learn more about Sable Island
Google Arts and Culture: A day-trip to Sable Island
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