Canada spans roughly ten million square kilometres and stretches from temperate latitudes north of the Great Lakes to the High Arctic islands, so it hosts an unusually wide range of terrestrial and aquatic biomes. The major ones include arctic tundra, boreal forest, temperate deciduous forest, prairie grassland, Pacific coastal temperate rainforest, montane and alpine zones, vast peatland complexes, freshwater lake and river systems, and arctic marine environments tied to sea ice. Because so much of the country lies at high latitude, the boreal forest alone accounts for a huge share of Canada’s landmass, but the smaller biomes at the edges are often the most ecologically distinctive and the most threatened.
Arctic Tundra
The tundra occupies Canada’s northern fringe, including the mainland coast above the treeline and most of the Arctic Archipelago. Winters are long and severe, summers are cool, and permafrost underlies virtually all of the ground. Plant life is limited to low-growing species: mosses, lichens, sedges, dwarf shrubs, and cushion plants. In the High Arctic, conditions become extreme enough that some areas qualify as polar desert. Research on polar-desert plant communities in the Canadian High Arctic found that the most barren sites, classified as polar barrens, averaged only about six plant species, with very low plant mass and almost negligible annual production, while slightly richer cushion-plant and snowflush communities supported around nine to thirteen species and considerably more biomass.1Ecography. Polar deserts, their plant cover and plant production in the Canadian High Arctic Soils in these areas show almost no horizon development, are alkaline, and are extremely low in organic matter and nutrients.
Even within the relatively uniform-looking tundra, climate change is reshaping plant communities at a visible pace. Across a roughly 15,000-square-kilometre area in the western Canadian Arctic, comparison of aerial photos from 1980 and 2013 showed clear expansion of erect dwarf and tall shrubs, coupled with declines in lichen cover on the ground. A winter temperature increase of about 4°C over that 30-year period appears to be the main driver, because warmer soils speed up nutrient cycling and give shrubs an advantage.2Ecosystems. Warming-Induced Shrub Expansion and Lichen Decline in the Western Canadian Arctic This “greening” of the tundra is not purely bad news for carbon budgets: recent work at an upland tundra site in the same region found that shrub densification can partly offset carbon losses from warming soils.3Journal of Geophysical Research: Biogeosciences. Shrub Expansion Can Counteract Carbon Losses From Warming Tundra Still, the overall trajectory is one of rapid compositional change that could fundamentally alter what “tundra” looks like within decades.
Boreal Forest
The boreal forest, or taiga, is Canada’s largest biome by area. It forms a broad band running from Newfoundland and Labrador west through Quebec, Ontario, Manitoba, Saskatchewan, Alberta, and into the Yukon and parts of British Columbia. Dominant trees include black spruce, white spruce, jack pine, balsam fir, tamarack, and paper birch. Fire is the primary agent of disturbance: large stand-replacing fires open the canopy, and the forest regenerates in a cycle that varies from a few decades to a couple of centuries depending on the region and the species involved.
What sets the southern boundary of the boreal forest? It is tempting to think of temperature alone, but research on the western Canadian boreal forest found that the southern limit corresponds most closely with moisture regimes, specifically the balance between annual precipitation and potential evaporation. Temperature measures like mean July temperature or growing-degree days showed an inconsistent relationship with where the forest gives way to grassland or parkland. The implication is that conifers fail to regenerate where moisture becomes limiting, not simply where it gets warmer.4Canadian Journal of Forest Research. Climate and the southern limit of the western Canadian boreal forest
That moisture dependency matters a great deal under a warming climate. Southern boreal forests already face increased risk of tree death from drought and more frequent fires. After those disturbances, deciduous hardwoods tend to replace the conifers that were there before, while jack pine and black spruce may persist mainly on the driest or wettest sites.5Environmental Reviews. A critical review of successional dynamics in boreal forests of North America In satellite-based analyses covering the entire boreal zone, browning and productivity declines were concentrated in the warmest, driest margins of the forest, while greening appeared along the northern edge, matching what you would expect from a biome slowly creeping northward.6PubMed Central. Satellite observations document trends consistent with a boreal forest biome shift
Peatlands and Wetlands
Embedded within and alongside the boreal forest is one of Canada’s most globally significant ecosystems: its peatlands. Bogs, fens, and other wetland types blanket enormous areas, particularly across the Hudson Bay Lowlands, northern Alberta, and parts of Quebec. Peatlands form when plant material, often Sphagnum moss, accumulates faster than it decomposes in waterlogged, acidic conditions. Over thousands of years this process builds up deep layers of peat that lock away carbon.
The numbers are striking. A national estimate of terrestrial carbon storage found that Canadian soils hold about 306 petagrams of organic carbon in the top metre, and roughly 98 of those petagrams sit in peatlands alone.7Global Biogeochemical Cycles. Large Soil Carbon Storage in Terrestrial Ecosystems of Canada That makes peatlands Canada’s single largest soil carbon reservoir. Fossil records from boreal continental peatlands show a common developmental trajectory: they typically began as mineral-rich fens dominated by brown mosses and gradually acidified over millennia, transitioning to Sphagnum-dominated bogs with water-table depths of 15 to 30 centimetres and pH values as low as 4.0.8Canadian Journal of Botany. Development of Sphagnum-dominated peatlands in boreal continental Canada
These systems are now under threat from two directions. A lower water table and more frequent droughts can undermine the mosses that build peat. Experimental work found that a deepened water table made Sphagnum mosses substantially more vulnerable to drought, and that species with smaller capitula (the dense “head” at the tip of the moss) were especially prone to damage.9Journal of Ecology. A deepened water table increases the vulnerability of peat mosses to periodic drought If drying and drought become frequent enough, lawn vegetation could shift rapidly to something else entirely, and the carbon-storage function could reverse.
Prairie Grasslands
South of the boreal forest in the interior of the continent, temperatures warm and moisture drops, giving way to the prairies. These grasslands stretch across southern Alberta, Saskatchewan, and Manitoba and represent Canada’s share of the Great Plains. Historically dominated by native grasses and wildflowers, the prairies supported vast herds of bison and a characteristic soil type: chernozem. The deep, dark topsoil of the prairies developed over thousands of years as grasses added large amounts of below-ground biomass that was then transformed by soil organisms, microbial activity, and periodic fire into complex organic compounds.10Canadian Journal of Soil Science. Chernozemic soils of Canada: Genesis, distribution, and classification
The prairies have been more dramatically altered by human activity than any other Canadian biome. Most of the native grassland has been converted to cropland, and what remains is fragmented into scattered conservation areas and rangelands. Drought at the boreal-prairie boundary has caused massive aspen dieback, offering a preview of how the transition zone between these two biomes could shift under continued warming.11Global Change Biology. Massive mortality of aspen following severe drought along the southern edge of the Canadian boreal forest If drought intensifies, the grassland boundary could migrate northward into areas currently occupied by forest.
Temperate Deciduous Forest
Tucked into the southernmost corners of Ontario, a small but biologically rich biome exists: the Carolinian, or deciduous, forest zone. This is the northern tip of a forest type that extends through much of the eastern United States. It supports species like tulip tree, sassafras, black walnut, and several oaks that are found nowhere else in Canada. Despite covering only about 0.25% of Canada’s land base, this zone supports roughly a quarter of the country’s human population, which has made it one of the most heavily developed and fragmented natural landscapes in the country.12Elsevier (Biological Conservation). Outcomes of longterm deciduous forest restoration in southwestern Ontario, Canada
The combination of high biodiversity and intense land-use pressure makes the Carolinian zone a perennial conservation priority. Restoration efforts have been underway for decades, with mixed success. The challenge is not just replanting trees; it is restoring the full suite of understorey plants, insects, and fungi that make these forests function. Because the zone sits at the northern edge of a much larger biome, its species are often already near their climate limits, and many are listed as threatened or endangered under Canadian law.
Pacific Coastal Temperate Rainforest
On the opposite side of the country, the Pacific coast of British Columbia supports dense temperate rainforest. Enormous annual rainfall, mild winter temperatures moderated by the ocean, and cool, foggy summers create conditions for some of the tallest and most massive trees in Canada, including western red cedar, Sitka spruce, and Douglas-fir. These forests are disproportionately carbon-dense. One analysis estimated tree biomass carbon stocks at roughly 211 to 218 megagrams of carbon per hectare. Despite accounting for only about 0.3% of global forest area, Pacific coastal temperate rainforest stores between 0.63% and 1.07% of global aboveground forest carbon as live tree biomass.13Canadian Journal of Forest Research. The distribution of tree biomass carbon within the Pacific Coastal Temperate Rainforest, a disproportionally carbon dense forest
One of the more fascinating features of coastal British Columbia’s forests is their connection to the ocean via salmon. When Pacific salmon return to spawn and die in coastal rivers, their carcasses deliver marine-derived nutrients to the riparian forest floor. Bears, eagles, and other animals drag carcasses onto the banks, and the nutrients are taken up by tree roots. This is not speculation: nitrogen isotope signatures in old-growth Sitka spruce heartwood rings were about 3 parts per mil higher in trees near salmon carcass deposits than in control trees, an effect that was largely independent of climate or tree age.14The Canadian Field-Naturalist. The carcass zone: salmon contribution to tree rings in old‑growth Sitka Spruce (Picea sitchensis) throughout coastal British Columbia The salmon-forest link is a vivid example of how marine and terrestrial biomes in Canada can be deeply intertwined.
Freshwater Lakes and Rivers
Canada holds an estimated 20 percent of the world’s surface freshwater, spread across millions of lakes and rivers. The Canadian Shield alone is dotted with countless lakes carved by glaciers and fed largely by precipitation. These shield lakes tend to be oligotrophic, meaning they have low nutrient levels and relatively clear water. Even so, they support full aquatic food webs. Research on Clear Lake in eastern Ontario, a small shield lake with minimal human influence, found it more productive than expected given its geological surroundings, with atmospheric precipitation serving as the main source of nitrogen and phosphorus.15Journal of the Fisheries Research Board of Canada. Nutrient Supply and Primary Production in Clear Lake, Eastern Ontario
Lake systems have also served as important natural laboratories. Canada’s Experimental Lakes Area in northwestern Ontario, a research station comprising dozens of small boreal lakes, has provided some of the most influential freshwater research in the world, including work on phosphorus cycling and eutrophication. In one of those experimentally fertilized lakes, researchers traced phosphorus movement using radioactive labeling and found that tiny microplankton held more than 90% of the added phosphorus, while larger phytoplankton and zooplankton took it up very slowly.16Canadian Journal of Fisheries and Aquatic Sciences. A Radiotracer Study of Phosphorus Cycling in a Eutrophic Canadian Shield Lake, Lake 227, Northwestern Ontario Findings like these shaped global policy on controlling phosphorus pollution in freshwater.
Arctic Marine and Sea-Ice Environments
Canada’s northern coastline borders three oceans and encloses a maze of channels, bays, and inlets that freeze over in winter. Sea ice is not a lifeless surface; it hosts communities of ice algae that grow in the bottom few centimetres of the ice, where dim light filters through. These algae form the base of the Arctic marine food web, feeding zooplankton, fish, and ultimately seals and polar bears. Measurements from a transect running from the Chukchi Sea to the Nansen Basin found that ice algae contributed an average of 57% of all primary production in the central Arctic Ocean.17Deep Sea Research Part II: Topical Studies in Oceanography. New measurements of phytoplankton and ice algal production in the Arctic Ocean
As ice thins and melt ponds proliferate, light penetrates more deeply, and the dynamics are shifting. A massive phytoplankton bloom was documented beneath fully consolidated pack ice in the Chukchi Sea, something that was not thought possible at such scale. Researchers suggested that satellite estimates of annual production in nutrient-rich Arctic shelf waters could be underestimated by as much as tenfold because satellites cannot see what grows beneath the ice.18PubMed. Massive phytoplankton blooms under Arctic sea ice Modeling work further suggests that the response of ice algae to warming is not straightforward: below 66°N, thinner snow cover advances bloom timing, while above 74°N, shifting ice seasons push the growing window into a more favorable photoperiod, actually increasing algal production.19PubMed Central. Sea-ice algal phenology in a warmer Arctic The ripple effects through the rest of the food web are expected to be large and hard to predict.
Indigenous Fire Management and Biome Maintenance
Some of Canada’s biomes owe their current or historical structure not just to climate and geology but to long-standing Indigenous land management. The Garry oak ecosystems of southern Vancouver Island are a case in point. Pollen and charcoal records show continuous and frequent prescribed burning by Indigenous peoples, with more severe fires occurring roughly every 26 to 41 years over the past 250 years. This burning maintained open oak woodlands. Once fire was excluded following European colonization and Indigenous population decline in the mid-1800s, Douglas-fir began recruiting continuously, and many sites have since succeeded from open oak woodland to closed conifer forest.20Biodiversity and Conservation. Environmental change in Garry oak (Quercus garryana) ecosystems: the evolution of an eco-cultural landscape Without active management, the Garry oak ecosystem effectively ceases to exist as an open woodland.
Similar patterns have been documented in coastal temperate rainforest, where fire was strongly associated with former Indigenous habitation sites during periods of occupation. People used fire as a tool to influence the density of specific plants, creating mosaics of vegetation at different successional stages.21Journal of Biogeography. Ecological legacies of anthropogenic burning in a British Columbia coastal temperate rain forest Recognizing these eco-cultural legacies is important because it means that “natural” is not always the right baseline for conservation. In some cases, the diverse, open landscapes that people associate with undisturbed wilderness were actually the product of deliberate human intervention sustained over centuries.
Permafrost Thaw and Shifting Boundaries
Permafrost underlies much of northern Canada and plays a structural role in several biomes. When it thaws, the physical landscape can change abruptly. Thermokarst processes, where ice-rich ground melts and the surface collapses, are accelerating. Remote-sensing studies have documented increasing rates of retrogressive thaw slumping, expansion of thermokarst lakes, and transformation of frozen peatlands into collapsed wetlands.22Permafrost and Periglacial Processes. Advances in Thermokarst Research In the Umiujaq region of northern Quebec, researchers tracked land-cover changes from 1986 to 2009 across a 60-square-kilometre area that straddles the forest-tundra boundary, documenting shifts in vegetation types and degradation of permafrost landforms called lithalsas.23Permafrost and Periglacial Processes. Assessing Permafrost Degradation and Land Cover Changes (1986–2009) using Remote Sensing Data over Umiujaq, Sub‐Arctic Québec
The Hudson Plains of Ontario, one of the largest peatland complexes on the planet, are similarly vulnerable. Air temperatures in the region are rising rapidly, driving unprecedented permafrost thaw, and the remoteness of the area has made it difficult to study how thaw is altering hydrology and land cover at larger scales.24Ecohydrology. Vulnerability assessment of peatland complexes in the Hudson Plains (Ontario, Canada) to permafrost‐thaw‐induced landcover and hydrological change using a multiscale approach The connection to biome classification is direct: when a frozen peatland collapses into a pond or a saturated wetland, the vegetation community transforms, the carbon dynamics flip, and the ecosystem effectively becomes something new.
Invasive Species and Boreal Resistance
One often overlooked question about Canada’s biomes is how well they resist invasion by non-native species. The boreal forest is surprisingly resilient on this front. Although more than 1,180 non-native species have been recorded in Canada’s boreal zone, most of them concentrated in Newfoundland and the southern boreal of Ontario and Quebec, the natural habitats themselves have shown strong resistance to establishment. Harsh climate, low light beneath dense canopy, poor soil nutrients, low pH, and thick ground cover of mosses all make it difficult for most invaders to get a foothold.25Environmental Reviews. Non-native species in Canada’s boreal zone: diversity, impacts, and risk
The biggest exceptions involve large vertebrates moved to islands, wildlife diseases, and earthworms. Earthworms are an under-appreciated ecological force in the boreal zone. Most of Canada’s boreal soils evolved without earthworms since the last glaciation, and the introduction of European species through fishing bait, road construction, and soil movement is altering the forest floor in ways that are hard to reverse. Earthworms consume the thick organic layer that many boreal plants depend on, changing nutrient cycling and sometimes displacing native understorey species. It is a slow-motion disruption that is easy to overlook but could accumulate over decades into a meaningful shift in how the forest floor functions.
How Past Climates Shaped What Grows Where
Canada’s current biome map is not static and never has been. During the early and middle Holocene, roughly 7,500 to 5,000 years ago, warmer conditions allowed temperate tree species like white pine and yellow birch to flourish well into what is now Quebec’s mixed boreal forest. Fossil data show that these species were considerably more abundant than they are today. Their subsequent decline was driven by a combination of cooler temperatures and severe fires in more recent centuries, along with a scarcity of suitable habitat.26Canadian Science Publishing (Botany). Vegetation and climate history of Quebec’s mixed boreal forest suggests greater abundance of temperate species during the early- and mid-Holocene The lesson is that the boundaries between Canada’s biomes have always moved in response to shifting climate, and the current arrangement is best understood as a snapshot rather than a permanent map. The speed of change, however, is something new: where past transitions played out over centuries or millennia, some of today’s shifts are measurable within a single human lifetime.