Savanna on the Pelee Island Alvar, Ontario (Photo by NCC)
Alvars of Ontario
Alvars are naturally open habitats with either a thin covering of soil or no soil over a base of limestone or dolostone. Globally, alvars are restricted to islands off the coast of Sweden, the eastern European Baltic region, the United Kingdom and Ireland, and the North American Great Lakes Basin. North American alvars support a distinctive set of flora and fauna, and over 60 percent of these alvars are located in Ontario.
Ontarians have a responsibility to conserve these globally significant habitats and their specialized species communities.
The unique characteristics that define an alvar also set the stage for the plants which grow there, and sometimes nowhere else. The five main alvar types are:
- alvar shrubland
- alvar grassland
- alvar savannah
- alvar pavement
- alvar woodland
Carden Alvar, Ontario (Photo by NCC)
Many alvars contain a multitude of at-risk and globally rare species, including a multitude of insects and the globally endangered eastern loggerhead shrike.
One of the most fascinating aspects of alvars is that they are among the most species-rich communities in the world at a small scale.
Carden Alvar was given the highest conservation ranking by the International Alvar Initiative and identified as a site of high significance by a report on Ontario alvars. This alvar is a complex of alvar grasslands, alvar shrubland, treed or partly treed ridges and slopes, and riparian wetlands including excellent quality alvar plant communities such as creeping juniper-shrubby cinquefoil alvar dwarf shrubland, poverty oat grass dry alvar grassland, tufted hairgrass wet alvar grassland, and juniper alvar shrubland.
Grike with maidenhair spleenwort, Ontario (Photo by NCC)
The Northern Bruce Peninsula and Manitoulin Island support some of the best examples of irreplaceable alvar habitat in the world and are key areas for alvar conservation in North America. These areas boast Ontario's best examples of alvar pavement, which consists of exposed rock with lichen and moss communities dominating the flora. Other plants, such as early saxifrage and maidenhair spleenwort, take root in the grikes, joint fractures in the limestone shaped by water erosion.
Stone Road Alvar on Pelee Island is designated as a provincially significant Area of Natural and Scientific Interest (ANSI). The site is a globally unique limestone plain or alvar not represented elsewhere in Ontario. Over 50 provincially rare plant species have been recorded at Stone Road Alvar, making it one of the most botanically significant sites in Ontario. Some alvar communities are dominated by shrubs, excluding many of the globally rare species that require open alvars. Conservation ownership and stewardship will ensure appropriate long-term management and conservation of alvars on Pelee Island.
Further east, Prince Edward County and the Napanee Plain also boast alvar habitat and support amazing rare species such as endangered juniper sedge.
Check out our downloadable and printable alvar factsheets: