Welcome to pitchersthistle.ca. This site has been created by the Pitcher's Thistle - Dune and Grasslands Recovery Team in Ontario, Canada. Please click on the RECOVERY TEAM link on the left to find out more about us and our purpose.

The words “fragile”, “rare”, “beautiful” and “threatened” have all been used to describe the coastal dune ecosystems of North America. Throughout the continent, dunes are the focus of conservation and recovery efforts. The Great Lakes shorelines support the most extensive freshwater dune systems in the world.  As the “Great Lakes province,” Ontario is host to many such dune sites, with some of the largest and most significant dune systems being found along the coast of Lake Huron.  

LAKE HURON DUNES

Most Lake Huron coastal dunes formed during the past 5,000 years at the heads of small coves, large arching bays, or on the tops of low forelands and baymouth bars.  Many of them consist of relatively low beach ridges. Others are more complex, having developed at the heads of large shallow bays on old beaches and plains left exposed when the postglacial Lake Nipissing retreated from near the modern Lake Huron coastline. Such dunes may reach heights of 30 m.

Many of the most extensive dune systems on the Lake Huron shoreline occur in the Manitoulin Island area.  Great Duck Island, off the southwest coast of Manitoulin, has the largest undisturbed dune system on the Canadian side of the lake.  Nearby, Western Duck Island supports the second largest.  On Manitoulin Island itself, Carter Bay and Providence Bay have major dune systems, and many smaller dune sites are found elsewhere along the south shore. 

Dune systems also occur along the southern coast of Lake Huron.  A major series of dunes stretches from Grand Bend through Pinery Provincial Park to the Ipperwash and Port Franks area.  Although much of it has been lost to development, this dune system still provides habitat for a great diversity of rare flora and fauna.  Dunes also occur at Inverhuron and MacGregor Point Provincial Parks, and at Southampton and Sauble Beach.  Wasaga Beach, Christian Island and surrounding islands on southern Georgian Bay have impressive dune ecosystems.

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RARE HABITATS AND ENDANGERED SPECIES

Freshwater dune systems are host to a unique suite of flora and fauna, including many globally rare, threatened and endangered species specially adapted to survive in the relatively harsh and unstable dune environment.  The isolation of Great Lakes dune habitats has resulted in unusually high numbers of species that occur nowhere else in the world (known as “endemics”). Great Lakes coastal dune systems are habitat for at least seven such flora and fauna.  These include the endangered Pitcher’s Thistle, as well as Great Lakes Wheatgrass, Gillman’s Goldenrod and Lake Huron Locust.

Ontario’s Great Lakes dune habitats have been grouped into seven distinct vegetation types, all of them ranked provincially very rare by Ontario’s Natural Heritage Information Centre [LINK], and all but one are considered globally rare.  Many of the habitats associated with the Huron dunes, such as backdune forests, dune savannahs, dune-associated wetlands, as well as Great Lakes coastal meadow marshes, are also rare and support species-at-risk.

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HOW ARE THE DUNES FORMED

Coastal dunes will only form where there is a source of abundant sand, such as areas near river mouths or in the vicinity of deposits left behind by glaciers. The sand is carried and deposited along the shore by water currents that run parallel to the coast.  Strong, steady on-shore winds then pick up finer sand grains and drop them in backshore areas, while coarser grains are rolled inland, building low beach ridges.  Pioneering grasses stabilize the ridges, which, if conditions are right, allow higher ridges or dunes to form.  Shrubs, like Sand Cherry and Common Juniper, and trees, like Balsam Poplar, are able to colonize these backdunes, further stabilizing the system. 

Where sand quantities, prevailing winds and water currents are ideal, major series of dune ridges may develop.  Moist areas, called pannes, often form in depressions between the dune ridges.  But natural storm events or high water levels can quickly break down dunes, resulting in blowouts.  In fact, water-level fluctuations influence dune formation, with dune growth accelerated by high water levels, when waves and storms erode away greater amounts of sediments from sand sources than when water levels are low. Relatively high water levels result in destabilization of the dunes, with increased sand movement and burial of forests.  Such a pattern of dune building and erosion is characteristic of most coastal dune systems and is necessary for the maintenance of open dune habitats.

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WHY ARE THE DUNES THREATENED

Even though natural disturbance is necessary for maintenance of open dune habitats, the intensity and form of impacts caused by human activities often exceed the natural resilience of dune systems.  Because coastal dunes are so often associated with popular sand beaches, they are particularly vulnerable.  Cottage and resort development on or near dune sites, and heavy recreational use of nearby beaches, result in losses of dune habitat.  Erosion and trampling by vehicle and foot traffic is often severe and can occur rapidly, even with relatively low levels of human use.  Shoreline and dune stabilization structures such as jetties, docks, piers and boardwalks affect the natural dynamics of the dune system by reducing the amount of sand available for deposition by water and wind.

The Pitcher’s Thistle – Lake Huron Dune Grasslands RECOVERY TEAM

Lake Huron dune grasslands provide the habitat critical to the survival of Pitcher’s Thistle, a nationally and provincially endangered species that is regulated as such in Ontario.  For each endangered and threatened species in Canada that is listed under Schedule 1 of the federal Species at Risk Act, a recovery team must be formed. Species are listed based on Status Reports and Assessments. The Recovery Team for Pitcher’s Thistle, created in 2000, is made up of representatives from Parks Canada, the Ontario Ministry of Natural Resources, the academic community, and other individuals with expertise in Pitcher’s Thistle and its dune grassland habitat.  The Recovery Team determined that the many rare and at-risk species native to the fragile and declining Lake Huron dune habitats (and one Pitcher’s Thistle site at Pukaskwa National Park on Lake Superior) would best be protected through a coordinated ecosystem-based approach, with Pitcher’s Thistle being the featured species.  

Recovery involves identifying the threats to species and their habitats, and defining solutions that reduce or eliminate these threats.  Recovery also involves undertaking activities to reverse the decline in population size or distribution, usually with the involvement of First Nations, government agencies, non-government organizations, private landowners, media, industry and the general public.

More on the, RECOVERY TEAM

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Author of www.pitchersthistle.ca: Jarmo Jalava, 2005

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