Almost one in four tree species in Canada is at risk of disappearing

Mar 21, 2023 | Edge of Extinction, Habitats, News, Species

Daniel Kraus

Daniel Kraus

Director of National Conservation at Wildlife Conservation Society Canada

My firewood pile has become a testament to the decline of Canada’s tree diversity. When I started cutting wood on our property over 25 years ago, I’d carefully deliberate over which trees would feed the woodstove over the winter. Today careful deliberation is no longer needed when I start up my chainsaw, because in large parts of the forest, most of the trees are dead.

In my lifetime I’ve watched as white ash, red ash, eastern flowering dogwood, and butternut joined American elm and chestnut as trees devasted by invasive pests and diseases. For example, emerald ash borer, first found in Canada in 2002, kills up to 99% of ash trees within 10 years of arriving in a forest. This loss of tree diversity is having a profound effect on our forest ecosystems, wildlife and the benefits that forests provide to people.

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Photo: White Ash by Janetg123 (iNaturalist).

Everyone knows that trees are important

In Canada trees define our geography, identity, and landscape experience. Our northlands are one of the few remaining places on the planet with large intact forests. Almost everyone can think of a tree that they climbed, planted or sat under to escape the summer sun. The benefits that trees provide to our communities – from temperature regulation to flood control – make them one of our most important allies in a rapidly changing world. 

We have been stewards of trees and forests for a very long time

Indigenous Peoples in North America tended diverse oak woodlands for thousands of years through traditional stewardship practices including prescribed fires. Next year marks the 400th anniversary of the publishing of Sylva, or A Discourse of Forest-Trees and the Propagation of Timber in His Majesty’s Dominions, arguably the first manual on forest restoration. Concerns about the loss of forests drove the creation of Algonquin Park in 1893 and Canada’s first school of forestry at the University of Toronto in 1907.

Photo: Algonquin Provincial Park.
Photo: Douglas firs in BC.

Yet, despite their known importance, the health of our forest ecosystems is failing

In southern Canada the fabric of forests has been mostly reduced to tattered isolated patches. In the remaining forests of this region, we are seeing the decline of forest diversity because of invasive species, incompatible harvesting, and climate change. In the north, climate change may move conditions faster than slow-moving trees can respond.

To mark International Day of Forests, WCS Canada examined the conservation status of Canada’s 234 native trees. These range from massive western red cedar in BC and Alberta to often shrub-like prickly ash in Ontario. The results were shocking – almost one in four tree species is at risk of disappearing from Canada or from the planet.

The greatest threats to these trees are habitat loss, invasive species and climate change

Some at-risk trees species found in Canada are threatened because of current or projected steep declines in numbers driven by introduced diseases or climate change (e.g., Butternut, Limber Pine). Others are threatened because they have small populations or ranges that make them vulnerable (e.g., Pacific Bayberry, Murray’s Birch).

Photo: Emerald ash borer by Kenneth Heiar (iNaturalist).
Photo: Eastern hemlock by Erik Danielsen (iNaturalist).

Every tree is its own ecosystem with insects and other wildlife that depend on them for survival

The essential role that trees play in wildlife habitat and ecosystems make our actions particularly critical for protecting biodiversity and halting extinctions. Some at-risk tree species, such as White Ash, Black Ash, Eastern Hemlock, and Whitebark Pine can be the dominant tree in forests. When these trees decline, the ecosystems they create and the species that live in those forests will also be at greater risk.

The good news is that we know many of the solutions

Recovery of some trees can be driven through habitat protection and restoration. We can help guide conservation actions for some at-risk trees by identifying Key Biodiversity Areas, such as Bickford Oak Woods in southern Ontario that harbours the nationally rare Swamp Cottonwood. Many of our rare trees can be propagated and planted into places where they have been lost. We can take steps, like not moving firewood long distances, to reduce the spread of invasive species and use community science platforms such as iNaturalist to report new occurrence of invasives. We can all take individual actions and support efforts to reduce carbon pollution and stabilize our climate.

Photo: Swamp cottonwood by Matt Reala (iNaturalist).
Photo: Forest in Long Beach in Tofino, BC.

There are signs of hope in my forest

Woodpeckers have discovered the bounty of a new food source, and native predatory insects are also starting to feed on the ash borer. Sugar maple is taking the place of ash, and in the most heavily hit areas I’ve planted burr oak to help fill and diversify the future forest canopy. And a few lone healthy ash trees still stand and may offer future hope for an ash return. But it is going to take many hands to restore the health of our forests, street trees and neighourhood tree canopies.  As the saying goes, the best time to plant a tree was 50 years ago.  The next best time is today.

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