S6

State of Canada’s Trees

This evaluation reports on the conservation status of tree species in Canada.

Almost

in 4 species of trees is at-risk in Canada.

Atrisk trees occur in every province of Canada. Ontario, Quebec, and BC have the highest number of atrisk trees.

The greatest threats to Canada’s at-risk trees are habitat loss, invasive species, and climate change. 

Why does the state of Canada’s trees matter?

Almost one in four species of trees is at risk in Canada. 

Canada has 234 species of native trees. This includes wild species, subspecies, varieties, or other important units of biological diversity. Of these, 57 have been assessed at risk in Canada or globally (Figure 1) (see Data Sources & Methods for definition of ‘tree’). 

Almost half of Canada’s at-risk trees are of global conservation concern and have been ranked as imperilled or vulnerable by NatureServe and/or Critically Endangered, Endangered, Vulnerable or Near Threatened on the IUCN Red List of Threatened Species 

At-risk trees occur in every province of Canada. Ontario (39), Quebec (12), and BC (11) have the highest number of at-risk trees (Figure 1). 

Four species of trees have disappeared from Canada. Four species are nationally endemic and do not occur in other countries. 

The greatest threats to Canada’s at-risk 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 (e.g., Butternut, Limber Pine). Others are threatened because they have small populations or ranges that makes them vulnerable to national or global extinction (e.g., Pacific Bayberry, Murray’s Birch). 

Many at-risk tree species with small ranges, such as Swamp Cottonwood in southern Ontario will trigger Key Biodiversity Areas. 

Insects and other wildlife depend on trees, and tree diversity, for their survival. The important role that trees play in wildlife habitat, ecosystem functions, and human well-being make our actions to conserve trees particularly critical for protecting biodiversity and halting extinctions.

Calls to action

Addressing the biodiversity crisis in Canada will require transformative change. See our backgrounder on transformative change for more information. Specific actions for the conservation of at-risk trees include:

Federal, provincial, territorial & Indigenous governments

  • Develop a robust National Biodiversity Strategy and Action Plan to implement the goals and targets of the Kunming-Montreal Biodiversity Framework, with a focus on protected and conserved areas, recovery of threatened species, and invasive species to help safeguard trees in Canada. 
  • Prevent the introduction and spread of invasive species and support research to develop biocontrols and other tools to manage existing invasive insects and diseases. Support implementation of existing invasive species strategies. 
  • Ensure tree planting and reforestation (including Canada’s Two Billion Tree Commitment) are conservation-focussed and include a variety of locally sourced native species. Include species that are rare and declining when they can be locally sourced, is biologically appropriate, and supports species recovery actions. 
  • Restore Indigenous land stewardship practices that promote tree diversity and ecosystem health and resilience. 
  • Support efforts to identify and conserve trees that are resistant to introduced pests and pathogens (e.g., Forest Gene Conservation Association). 
  • Establish and effectively manage and restore protected and conserved areas to protect the habitat for at-risk trees, particularly those with small ranges. 
  • Invest in actions to accelerate the identification and conservation of Key Biodiversity Areas in Canada that include at-risk tree species. 
  • Support Conservation Data Centres across Canada to continue to survey and rank at-risk trees. 

 Local governments & communities

  • Develop programs and capacity to monitor and manage invasive species. 
  • Inventory and protect at-risk tree species in your jurisdiction. 
  • Include at-risk and other native trees in planting projects where biologically appropriate.

Civil societies, community organizations, universities, colleges & museums

  • Target arisk tree species for land protection and stewardship actions. 
  • Research how planting atrisk tree species outside of their current range and conserving climate refugia could help them to adapt to climate change.  
  • Develop and maintain seed banks for atrisk tree species in Canada that capture genetic diversity across their range. 
  • Support and advocate for the designation of Key Biodiversity Areas that include atrisk tree species with small ranges.

Businesses & corporations

  • Avoid projects that could impact at-risk tree species and their habitat and seek opportunities for ‘nature-positive’ actions that will improve their status. 
  • “Adopt” a- risk tree species and fund communities and organizations that are protecting these species.

Everyone

  • Learn and talk about atrisk tree species found in your area. If possible, source locally grown atrisk trees and grow them. 
  • Support early detection of invasive species. Learn about these species in your areas and report sightings using iNaturalist or EDDMapS. 
  • Join societies and local groups that advocate for the conservation of threatened biodiversity. 
  • Support Key Biodiversity Areas or other conservation projects near you that help to highlight and conserve at-risk trees and other threatened species. Volunteer as a KBA caretaker or create a caretaker group.

Other information

NatureServe and the IUCN Red List use complimentary, but different criteria for assessing conservation status. Status assessments by NatureServe have been completed for a much larger number of species than IUCN Red List assessments. 

Additional background in species assessments can be found in in our backgrounder on species assessment and these sites:

IUCN Red List

NatureServe

COSEWIC

Confidence and limitations

High confidence – this information is based on published assessments by the IUCN Red List and status ranks assigned by NatureServe. 

Most species of trees have been identified and ranked in Canada. Not all the tree species that we included may meet the definition of a ‘tree’ throughout their range (see Data Sources & Methods). 

Data sources & methods

The list of tree species was developed based on lists of trees from five different sources: 

  • Natural Resources Canada – Index of Trees
  • Database of Vascular Plants of Canada (VASCAN) – Checklist builder (Plants with the habit: ‘trees’) 
  • State of the World’s Trees – Global Tree Portal – Country Search (‘Canada’) 
  • Data sharing for conservation: A standardized checklist of US native tree species and threat assessments to prioritize and coordinate action (Carrero et al., 2022)Supporting Information 
  • Trees Canada – Trees of Canada online database 

These lists, and field guides of trees in Canada (e.g., Lauriault, 1989) all have variations on the number of native tree species found in Canada and the definition of ‘tree’. We followed the definition of Beech et al. (2017) used by Carrero et al. (2022), the IUCN Global Tree Specialist Group, and the standard for the Global Tree Assessment initiative:

A tree is a woody plant with usually a single stem growing to a height of at least two meters, or if multi-stemmed, then at least one vertical stem five centimeters in diameter at breast height. 

There are several species on our list, such as Smooth Alder, Eastern Burning Bush, and Dwarf Hackberry that, depending on location and site conditions, may not always meet the definition of tree we use in this analysis. 

We included tree species and infraspecies but not hybrids. The final list of trees from Canada was cross-checked with most recent information in NatureServe Biotics database to confirm they are native to Canada. The NatureServe Biotics database was also used to identify national and global status and range in Canada. Species with rounded national ranks of N1, N2, N3, NH and NX were included, along with species assessed on the IUCN Red List of Threatened Species as Critically Endangered, Endangered, Vulnerable, and Near Threatened. 

The preliminary assessment of threats was based on published information in Red List and COSEWIC assessments and ranking information by NatureServe. Threats were categorized based on the IUCN threats classification. Threat categories of 1.1 Housing & urban areas, 2.1 Annual & perennial non-timber crops, 2.2 Wood & pulp plantations, and 3.2 Mining & quarrying were combined as ‘habitat loss’.  

See our backgrounder on species assessments for more information on the methods used by NatureServe, COSEWIC and the IUCN Red List.

S5_New sea sponge_Sally Leys

White Ash numbers have been devasted by the invasive Emerald Ash Borer.

Photo: Owen Clarkin (iNaturalist).

S5_Hine's Emerald_Bonnie Kinder

Yukon Lodgepole Pine is a newly described variety of Lodgepole Pine that is endemic to Canada and currently only documented from high elevations in Yukon. These habitats are rapidly shifting because of climate change.

Photo: Bruce Bennett (iNaturalist).

Applications and next steps

Protecting and restoring at-risk trees will make an important contribution to global efforts to halt and reverse species and ecosystem declines. While recovery of some trees can be accomplished through habitat protection and restoration, and conservation translocations, at-risk tree species threatened by invasive species and climate change will require long term strategies. Some rapidly declining trees, such as Black Ash, Eastern Hemlock, and Whitebark Pine, are the main tree in some forest ecosystems. When these dominant trees decline the composition, structure, and function of these forests can be rapidly altered. For example, up to 99% of all ash trees are killed within 10 years once the invasive Emerald Ash Borer arrives in an area. As these trees decline, the ecosystems they create and the species that live in those forests will also be at greater risk. 

Trees provide many benefits to people including temperature regulation, flood control, wood, and food. Several of the trees at risk are important to Indigenous Peoples, such as Black Ash, and these culturally significant species will be highlighted in future evaluations. 

Mapping the range of at-risk tree species would support ‘hot-spot’ mapping of priority areas to target on-the-ground conservation actions. 

There are other trees that are rapidly declining such as American Beech (as a result of an introduced fungus) are likely to be assessed as at risk in the future and added to this list.

S6_F1_State-of-Canada's-trees-2023

Figure 1. Canada’s atrisk tree species.

Related Evaluations

S2: Globally Threatened Species 

S3: Species at Risk 

H1: Globally Threatened Ecosystems

For More Information

Contact us for more information or for a copy of the data at https://shapeofnature.ca/take-action/ or wcscanada@wcs.org

Updates

This evaluation is updated every two years on International Day of Forests (March 21). Next update is in 2025.

Partnership

This SHAPE of Nature has been created in partnership with:

https://www.natureserve.org/canada

How to Cite

Wildlife Conservation Society (WCS) Canada & NatureServe Canada. 2023. State of Canada’s trees 2023 (version 1.0), in SHAPE of Nature. https://shapeofnature.ca/

Prepared by: Wildlife Conservation Society Canada (Dan Kraus) 

Reviewers:  

BC Conservation Data Centre (Ryan Batten, Jacqueline Clare, Marta Donovan, Jenifer Penny)  

Atlantic Canada Conservation Data Centre (Sean Blaney) 

NatureServe Canada (Amie Enns, Patrick Henry) 

Ontario Natural Heritage Information Centre (Wasyl Bakowsky, Sam Brinker) 

Wildlife Conservation Society Canada (Ciara Raudsepp-Hearne, Justina Ray) 

Yukon Conservation Data Centre (Bruce Bennett) 

Species

S1 Edge of Extinction

S2 Globally Threatened Species

S3 Species at Risk

S4 Endemic Species

S5 Knowledge of Species

S6 State of Canada's Trees

S7 State of Canada's Whales

S8 State of Canada's Frogs

Habitats

H1 Globally Threatened Ecosystems

H2 Peatlands

H3 Roads

Actions

A1 Protected & Conserved Areas

A2 Recovery Plans for Species at Risk

Policies

P1 Biodiversity Laws, Policies & Plans

P2 Provincial & Territorial Species at Risk Laws

P3 Delays in Protecting Species at Risk