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Post-Fiona Dune Recovery

Many people were heartbroken at the sight of PEI’s world-famous sand dunes following Hurricane Fiona last fall. At the time, I wrote about this dramatic change being only temporary and that the dunes will recover naturally. Nearly one year later, I’m happy to give you an update!

Photo 1: PEI's coastal sand dunes saw a lot of erosion - many metres in places - from Hurricane Fiona in September 2022. Photo by Brian McInnis, used with permission.

First, a reminder of the situation a year ago. Photo 1 shows just one example of the impacts of hurricane-force winds and storm surge along the Island’s north shore (photo by Brian McInnis, used with permission). It was very much like a huge knife had sliced away many metres of dune, exposing Marram Grass roots like a skeleton under skin (Photo 2). I think of our coastal beaches and dunes like a bank account, with continual deposits and withdrawals of sand throughout the year. Fiona made a huge withdrawal. Fortunately, the steady and reliable income stream – offshore sand – was not only still there, it had grown from the storm.

Photo 2: Hurricane-force winds and storm surge sheared away the seaward side of the dunes, exposing the skeleton of Marram Grass roots underneath. Photo from September 2022.

The sand Fiona washed away didn’t go far, and a combination of water, wind, plants, and fungi has been working together to bring it back and rebuild the dunes. Offshore currents move sediment along the Island’s coast, and tides bring it ashore. From here, wind takes over as the driving force. As the newly arrived sand dries out, wind picks it up and carries it further inland, where it gets packed against the seaward side of the eroded dunes and caught by plants such as Sea Rocket (Cakile edentula) growing on the beach (Photo 3). Marram Grass (Ammophila breviligulata) moves in and begins to both hold the fresh sand and catch even more (Photo 4). ‘Ammophila’ appropriately translates as ‘sand lover’, and as this grass gets buried in sand it will grow up through it, eventually recreating a skeleton holding the new dunes together. Unseen but playing an important role in all of this are the mycorrhizal fungi that help plants grow in this unforgiving environment.

Photo 3: This is the site in Photo 2 shown 11 months later. Huge quantities of sand have returned through natural coastal processes.

Last fall, there were some who thought it would be necessary to truck in sand to rebuild the dunes. I ran some quick calculations, and for every 10 metre linear distance of dune shown in Photo 3 there’s more than 50 cubic metres (about 1,800 cubic feet, or roughly 66 cubic yards) of new sand. An average dump truck holds 10 to 14 cubic yards; let’s call it 11 to make the math easy. Natural processes have already returned an estimated six dump trucks of sand for every 10 metres of dune, or the equivalent of roughly 3,000 truckloads on this one site alone! Note that these are not high dunes – only about three metres (10 feet) – and my back-of-the-envelope calculations don’t include all the new sand on the beach or that which has blown even further inland.

Photo 4: Water and wind bring sand ashore, and plants such as Marram Grass - a keystone species in this habitat - begin the rebuilding process.

Much like the crumple zone on a car, sand dunes are built to absorb the brunt of coastal storms and protect the land behind them. These essential ecosystems are naturally resilient, capable of rebuilding themselves after events like Fiona. Giving our dunes time and space (and hoping for a quiet storm season for the next few years), is what’s needed to finish the well-underway recovery of this part of PEI untamed!

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