Sat. Feb 24th, 2024

Today’s post comes from Alistair MacKenzie, our natural heritage education and resource management supervisor at Pinery Provincial Park.

In a province dominated by the rock of the Canadian Shield, sand is scarce. If we combined all of Ontario’s coastal sand dunes, they would only represent less than 0.5% of our province’s land area.

We can thank one simple fact of nature for the creation of Pinery Provincial Park and its rare dunes: namely, that temperature differences between the air above Lake Huron and the adjacent land mass create a coastal breeze.

The creation of the dunes.

pinería coastal cellThe littoral cell shown on the right has been responsible for the creation of the entire landmass of Pinery Provincial Park over the past 6,000 to 8,000 years.

As the levels of ancient Lake Nipissing receded, erosion and deposition moved sand and rock southward from the source sites (north of present-day Grand Bend) to the sink site (between Grand Bend and Kettle Point).

While Pinery generally gains sand each year, lake levels have occasionally risen and eroded the material away from Pinery’s shoreline.

This classic cycle of ebb and flow has created a landscape that is always changing. In some periods, Pinery grows; in others, it returns part of its sand to the lake.

cobblestones in dunesAmong the immense sand deposits are bands of cobblestones, marking ancient shorelines stranded by the drop in lake levels.

If you have visited the park in the last decade, you will know that we are currently in the middle of a period of ebb and the park’s coastal dunes are eroding.

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Embryo dunes

As mentioned above, the shore breeze is always present, sometimes diminished to a faint whiff, but at other times sweeps over the surface of Lake Huron to hit the Pinery shoreline. Regardless of its strength, the breeze carries grains of sand from the beach inland, creating small piles of sand known as dune embryos.

The diagram below shows how Pinery grows when lake levels are lower.

Embryo dunes

Sand eroded from the north of the park is transported south by coastal drift and deposited on the coast between Grand Bend and Kettle Point. When the waves recede, the sand grains left on the shoreline dry out and are then blown toward the face of the dune by the offshore breeze.

Saltation is the method by which sand grains jump and bounce off the beach and dune faces. Dunes begin to grow when grains of sand are dropped by the wind and begin to accumulate behind beach debris. Therefore, what appears to some to be unsightly rubble is actually the very foundation of the park. Dunes cannot form without logs and other natural objects washing ashore.

records on the beach

From here, the most important plant in the park is in charge of turning small piles of sand into imposing dunes, sometimes many stories high.

marram grass

Marram grass (Ammophila breviligulata) is an amazing species that is perfectly adapted to life in the sand; Able to withstand burial in up to a meter of sand per year, it withstands the scorching desert temperatures of summer and the freezing cold of winter.

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Breaking the grass in Pinery

Marram Grass could not be more suitable for dune creation if it were intentionally designed by humans. Marram Grass spreads and grows in three key ways:

  • It produces seeds that are dispersed by the wind.
  • It grows clonally by increasing the number of stems in a clump each growing season.
  • It grows clonally by spreading rhizomes (underground stems) horizontally along the dune face below the sand surface.
  • This final ability to develop rhizomes leads to the formation of a fishing net-like network of plant matter along the face of the dune. There is nothing more suitable for turning small mounds of sand into imposing dunes than Marram Grass.

    Microclimates and ecological succession.

    This pattern of embryonic dunes converted into towering dunes by Marram Grass, along with receding lake levels over the past few thousand years, has resulted in an undulating landform that leads to the next surprising aspect of Pinery: microclimates.

    Dune cross section

    Each dune face at Pinery, whether newly formed or stabilized and ancient, has shaded slopes and sun-kissed ones. This variability leads to a variety of microclimates that provide the conditions necessary for thousands upon thousands of life forms to thrive.

    As time passes, ecological succession takes over slowly adding more and more species and stabilizing the sand. Finally, an oak savanna is established over the stabilized dunes.

    Protecting our dunes

    You play a key role in keeping this natural process intact.

    woman looking towards the beach

    We need our visitors to follow established trails and stay off dune slopes. This will help the ecological integrity of the Pinery thrive.

    Stop by the Visitor Center to talk to a park naturalist about our dunes or to discover volunteer opportunities with the Friends of Pinery Park.