Today we have another of PEI's lesser-known coastal habitats: Grey Dunes (Photo 1).
The sand dunes featured in Island photos are almost always primary dunes (aka Yellow Dunes). A few special places on PEI have the right conditions for much older, stable sand dunes to form. These dunes are typically covered in lichens and thin soil, giving them a greyish appearance and the name Grey Dunes.
Grey Dune formation requires a large and continuous supply of sand, something eastern PEI has in spades. Offshore currents move sand from west to east along the north shore, and it ends up in a huge underwater sand bank off East Point. From here, storms and tides push it into the Strait, where it supplies the five-kilometre-long South Lake sandspit as well as Grey Dunes at Basin Head and Black Pond.
Grey Dunes start out as primary dunes, right behind the beach. As more sand moves in, additional dunes develop seaward, buffering the older dunes from coastal weather. This means the sand on the older dunes doesn’t blow around as much, and lichens and plants can colonize, stabilizing the sand even further. Eventually - after thousands of years - you have Grey Dunes.
So, why do we have a long spit at South Lake and Grey Dunes at Basin Head and Black Pond? It all comes down to geography. The latter two sites started as coves with sandstone headlands to their west. Sand filled in the coves, but the headlands prevented any further westward migration. As a result, the dunes continued to build seaward rather than forming a long spit.
These aren’t the only places with Grey Dunes on PEI, but they are among our best examples. Grey Dunes are home to interesting and specially-adapted lichens, fungi and plants. Reindeer lichens (Cladonia spp.) characteristic of the far north thrive here. Earthstar fungi (Astraeus smithii, Photo 2) grow here and act like little hygrometers: in wet weather, they open their star-like outer arms to reveal the spore sac inside, closing again in dry weather to protect the spores. Provincially uncommon plants Juniper (Juniperus communis, the needle leaves and bluish berries in Photo 3), Bearberry (Arctostaphylos uva-ursi, the flat green leaves in Photo 3) and Woolly Beach-heath (Hudsonia tomentosa) all call Grey Dunes home.
Grey Dunes are stable but also fragile: careless foot traffic can leave imprints that last for decades. While many Island habitats can sustain visitation, this one is best appreciated from afar.
A cool - and rare - PEI landscape!