Rising from the ashes: ecological renewal at Waterton Lakes National Park

Any intense natural process like a wildfire will give rise to stories of loss, sacrifice, renewal… and stubbornness.

In September 2017, the Kenow Wildfire swept through Waterton Lakes National Park in Alberta.

Before the wildfire moved into the park, a team of bison experts from Grasslands National Park in Saskatchewan arrived to help round up Waterton’s bison herd.

But one bull refused to go.

The wildfire eventually burned through the bison paddock, but the bull survived, probably by taking refuge in one of the large ponds.

That resilient bison—red-eyed and ash-flecked but undefeated—might be a good symbol for the entire park.

Extreme ecological change has taken place in this stunning mosaic of grassland, forest, lakes, ponds, and rivers. But nature is already renewing itself by weaving the mosaic anew—and perhaps by adding novel, unexpected patterns.

Nothing constant but change

All landscapes undergo a natural cycle of disturbance (fire, flood, drought, insects, and disease) and renewal.

For park visitors, scientists and park staff, life after Kenow offers a rare chance to see how a national park regenerates following an extreme wildfire.

“Ecological renewal may take some time,” says Kimberly Pearson, one of Waterton’s ecosystem scientists, “and the results may look very different than we’re accustomed to.”

But ecological renewal is already taking place. It began soon after the ground cooled.

In the weeks following the fire, beargrass (a mountain lily and one of the park’s most identifiable plants) appeared to have re-sprouted at higher elevations. This happened in severely burned areas, where all organic vegetation and soil were removed by the extremely intense fire.

The pattern of renewal

Renewal after a wildfire depends in part on the fire’s severity—that is, on the change to vegetation and soils caused by fire. In the case of the Kenow Wildfire, 44 per cent of the park’s vegetated area was burned with high or very high severity.

In a forest, a high-severity fire removes about seventy per cent of the tree canopy. The ground surface is reduced to mainly ash or mineral soil (that is, soil derived from rock and minerals, without the organic “earthy” part).

In a burn of very high severity, no tree canopy remains, and the forest has been replaced by blackened tree trunks. The seed bank in the soil may be largely destroyed.

But Waterton’s landscape has evolved with wildfire, and nature is expert at repairing such disturbances. Forests that may appear destroyed or lifeless are very much alive and provide a canvas for renewal.

Tree seeds can blow in from unburned canopies nearby, or even from distant forests. Most tree seeds that will take hold in Waterton, says Ms. Pearson, will probably be long-distance dispersers from BC or Montana.

Tree seeds can also be left behind by red squirrels that cached them underground before the wildfire and, with the arrival of spring, brought them to the forest floor to feed on.

Grasslands—a vital part of Waterton’s ecosystem—have historically been shaped by fire. Periodic wildfires and those used strategically by First Nations kept the grasslands free of shrub and aspen, and promoted renewal of grasses and wildflowers.

Monitoring and controlling invasive plants becomes especially important given the large area of ground disturbed by Kenow. Non-native invasive plants thrive in areas affected by disturbances such as fire. The park’s innovative, well-established invasive plant management program is well equipped to minimize the impacts on natural diversity.

Water and wildlife

A changed landscape means changes to the streams, rivers, ponds and lakes. Because so much vegetation and soil have been burnt, more sediment will be carried by water into streams and rivers.

Attached to this sediment will be phosphorus, which boosts aquatic plant growth. In many creeks, the colourful rocks that are so unique to this area are expected to become darkened, covered in small, dark algae.

The post-fire landscape will also mean a change in foraging habits for wildlife. Bears, for example, have lost a lot of their favourite berry-producing plants. The animals will concentrate in areas where berries and other food sources remain. Bears are opportunistic feeders and will be alert for alternative food sources. This makes it even more important for visitors to keep their food and garbage secure in bear-proof containers.

Although the park lost at least 40 individual large mammals to the wildfire—including deer, elk, moose and black bear—the region’s wildlife populations remain healthy.

Some uncommon animals are also expected to take hold. Burned forests attract insects, which in turn attract post-fire specialist birds such as three-toed and black-backed woodpeckers. These birds were rare in the park in the years before the Kenow Wildfire.

It is an exciting time to be part of this landscape, says Ms. Pearson. Some aspects of ecological renewal may be beyond the scope of our lifetimes, but other changes are already unfolding.

And what of Waterton’s bison herd that had to be moved because of the fire? They should be back—eventually. Parks Canada plans to return them to the park once their native grassland habitat has renewed itself.