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Churning waters and wind gusts exceeding 100 kilometres per hour powered by post-tropical storm Fiona gnawed through large parts of Prince Edward Island National Park in September, leaving behind a changed coastline.

Experts worry the beaches and sand dunes may not have enough time to recover before the next storm hits.

Parks Canada spokesman James Eastham described the damage from Fiona as "very striking" and "quite obvious."

"Based off of our initial assessments, there's between three and 10 metres of coastal erosion in various locations around the park," he said, adding that it's too early to get a complete portrait of the attrition of dunes and upheaval of wildlife habitat caused by Fiona.

Following the storm, much of the area in and around the communities of Cavendish-North Rustico, Brackley-Dalvay and Greenwich was a picture of torn trees and washed coastlines, Eastham said. Green Gables Heritage Place, Ardgowan National Historic Site and Skmaqn—Port-la-Joye—Fort Amherst National Historic Site were also damaged by the storm, he added.

The climate station at Red Head, owned by the Mi’kmaq Confederacy of PEI, recorded a peak wind speed of 133 kilometres per hour at 5 a.m. on Sept. 24. A peak water level of 2.69 metres above datum — the tidal reference point — was recorded at 5:55 a.m.

Prof. Chris Houser, from the University of Windsor's school of environment, said coastal ecosystems are always in flux — waves and wind shift sands over years. 

"But what we saw in Fiona was a very large storm that hit at high tide — a very large storm surge and very large waves and as a result, a large section of the beach and a large part of the dune were eroded," he said. 

The affected areas will eventually make a full recovery, but it could take a "considerable amount of time," Houser said. 

"It could take well over a decade, in fact, several decades for that recovery to be complete."

The problem, however, is whether P.E.I. has the time to recover before the next major episode of erosion, Houser said.

"So the question is, are we going to have enough time for recovery before the next storm, whether that be in the winter, or whether that be another hurricane?"

P.E.I.'s sand dunes are familiar with harsh storms.

A Sept. 30, 1923, storm with heavy winds produced large waves and surges causing extensive dune erosion that took several decades to heal, Houser said. A 2010 study about the evolution of dunes in P.E.I. said newspaper records show the storm surge from the 1923 deluge affected more than 50 bridges — many of them were washed away or left impassable across fishing harbours along the north shore.

Houser said Fiona did not cause extensive overwash — the flow of water over dunes — but he said an increase in the number of large storms could create a similar effect. "Now we're in a position where water levels are rising. Sea ice is becoming less common. There's less sea ice for less amount of time."

Aside from the erosion to the Island's famous sand dunes, Fiona caused damage to other parts of the ecosystem as well, Eastham said. Parks Canada will do more in-depth aerial surveys in the coming weeks and compare data from before and after the storm to get a more complete picture of Fiona's destruction, he added.

While piping plovers and bank swallows had already taken flight south before Fiona hit, he said ecologists will be closely monitoring coastal ecosystems and at-risk species over the coming year to see how the storm affected the animals and their habitats.

"We do know that some species like bank swallows rely on those newly exposed sandbanks to build their nests," he said.

"Our ecologist will be monitoring (piping plovers and bank swallows) closely when they return to get a sense of the impacts that the storm may have had on those species."

Fiona might have also affected freshwater and wetland species because of the large amount of debris, sand and salt water that washed into areas near the shore, he said.  

"You walk around and it's just a little bit striking,"  Eastham said. "You can tell how much more sand dunes there used to be in a lot of places, and just think what the ocean must have been like to erode that much .... Just crazy." 

This report by The Canadian Press was first published Oct. 10, 2022.

Hina Alam, The Canadian Press