Key finding overview
KEY FINDING 1. At a national level, the extent of forests has changed little since 1990; at a regional level, loss of forest extent is significant in some places. The structure of some Canadian forests, including species composition, age classes, and size of intact patches of forest, has changed over longer time frames.
This key finding is divided into five sections:
- Key finding overview (this page)
- Changes in the treeline zone
- Intactness of Canada's landscapes
- Shift from late-succession to early-succession forests
Forests are dynamic and diverse ecosystems, where complex interactions occur between species and ecological processes, from below ground to high in the canopy. Forests are important to biodiversity because they provide habitat for a wide array of plant and animal species from microorganisms to large mammals and because they are a pool of genetic diversity. It is estimated that approximately two–thirds of the species in Canada are associated with forests for at least part of their life cycle.1, 2 Forests also provide ecosystem services, including the regulation of water flow across the landscape, erosion control, water purification, climate stabilization, and immense economic benefits.
There are two forest bioclimatic zones in Canada - boreal and temperate. Each zone possesses a unique geography, vegetation, climate, soil, and wildlife. Canada has approximately 24 and 15% of the world's boreal and temperate forests,3-5 and 9% of the world's total forest cover.4 The boreal forest stretches across eight ecozones+ (see map). It is the largest contiguous forest ecosystem on Earth, and Canada's largest biome, covering 25% of its total land area and 72% of its total forest area.1
Spruce forests dominate all boreal forest ecozones+.5 Black spruce forests are of particular ecological significance because of their nearly continuous ground cover of lichens, feather mosses, and sphagnum mosses. Lichens are critical forage for wintering migratory caribou herds and mosses provide habitat for a number of species. In northern Quebec, 9% of the dense black spruce forest has shifted to lichen-woodland systems over the past 50 years.6 The proportion of the boreal forest that is dominated by spruce has decreased in the managed forest portion of Ontario's Boreal Shield,7 and in the southern part of Manitoba's Boreal Shield.8 Spruce is also declining outside the boreal forest.9,10
The temperate forest stretches across six ecozones+ and tree species are more variable. Dominant species include spruce and maple in the Atlantic Maritime, deciduous species in the Carolinian forest of the Mixedwood Plains, spruce and pine in the Montane Cordillera, and hemlock in the Pacific Maritime.5
The total forest area in Canada is approximately 3.48 million km2.15 From 1990 to 2007, the annual area deforested – permanently converted from forests to other land cover – ranged from 482 to 760 km2, an annual rate of deforestation of 0.01 to 0.02%. This is a very small loss when compared to the global rate of deforestation and the extent of Canada's forests.12, 16 Trends in total forest area, including afforestation – the expansion of forests into other land cover types - cannot be calculated from available data. Conversion of forest land to cropland, resource roads, transmission lines, oil and gas development, urban development, and flooding for new hydro reservoirs, contributes to deforestation.13 The rate of deforestation is small at a national level, but it can be significant in some regions. For example, 45% of the highly forested coastal Douglas fir zone in B.C. has been converted to other land cover types.17 A small amount of afforestation is occurring in the Ontario portion of the Mixedwood Plains Ecozone+, where forest cover has rebounded from a low of 11% in the 1920s to an average of 22% today.18
Changes in the treeline zone
The term "treeline" is deceptive – there is not a sharp line where trees end, but rather a zone of transition from increasingly sparse trees to tundra. Treeline zones in Canada are both latitudinal, across the north of the country, and altitudinal, on the slopes of hills and mountains. The emerging picture is one of change, but not a uniform expansion of the treeline. In northern Quebec, trees in the forest-tundra zone have grown faster and taller since the 1970s19 but distribution of trees has not changed greatly.20 In Labrador, treelines have expanded northward and up slopes over the past 50 years along the coast, but not inland.21 In the mountains of northwestern Canada, tree growth and density have changed more than the position of alpine treelines.22
A study on the treeline in western Canada found only a small net increase in tree cover, but major changes in vegetation within the treeline zone. Tree cover increased in the northern half of the zone, but this was mainly offset by decreases in the southern half, especially west of the Mackenzie Delta – likely related to drier conditions due to higher temperatures.24 The biggest changes were an increase in shrubs and, in the northwest of the treeline zone, a replacement of lichen cover and bare land with small, non–woody plants (herbs).
Since 1900, treeline has advanced at 52% of the 166 sites examined around the world and has receded at only 1% of the sites.25
Gros Morne National Park, Newfoundland and Labrador
Intactness of Canada's landscapes
Canada is one of the few countries that still have large tracts of forests, relatively undisturbed by human activity, that are believed to contain most of their native biodiversity. Just how intact Canada's forests are depends on how they are measured and, as Long et al.26 point out, measuring intactness, or its corollary, fragmentation, can be complex. Global Forest Watch measured intact landscapes as undisturbed areas, free from human impact, and at least 50 km2 in size for the boreal and taiga forest ecozones, and 10 km2 for temperate forest ecozones.27 B.C. defined intact coastal rainforests as undisturbed landscapes greater than 500 km2.17 The Alberta Biodiversity Monitoring Institute has taken a different approach, measuring intactness as a percentage of what would be expected in a pristine habitat.28
Global Forest Watch has published the only national perspective on intactness (see map) concluding that almost 50% of Canada's total land area, and more than 50% of the area of Canada's forested ecozones, consist of intact forest landscapes. This includes 94% of the northern boreal ecozones (using the Terrestrial Ecozones of Canada classification system29) – Taiga Cordillera, Boreal Cordillera, Hudson Plains, and Taiga Shield – and 73% of the Taiga Plains. The southern boreal regions are more impacted by human activities. Thirty-seven percent of the Boreal Plains remains as intact forest landscapes. About 42% of the temperate forest ecozones remains as intact forest landscapes. Ninety percent of this area is in B.C., the remainder is in Alberta.27 In North America, the only remaining intact coastal temperate rainforest is in B.C. and Alaska. Approximately one-third of B.C.'s remaining coastal temperate rainforest is intact, in patches greater than 500 km2.17
Forest fragmentation occurs when large, continuous forests are broken up into smaller patches. It can result from human activities such as clearing for agriculture, urbanization, oil and gas exploration, and roads,30 as well as from natural processes such as fire and insect infestations.31, 32 Natural disturbance is discussed elsewhere in this report; the discussion here focuses only on fragmentation from human activities. The impact of forest fragmentation by human activities is dependant on the species and the spatial scale. Impacts can include: declines in neotropical migrant and resident birds requiring interior forest habitat;33 declines in species with large area requirements, such as grizzly bear and caribou; increases in species that prefer to browse along forest edges, such as moose; increased exposure of interior forest species to predators and parasites; disruption of social structure of some species34 and barriers to dispersal.30 Sustainable forest practices can be designed to mitigate the effects of fragmentation.
Intactness of old forest habitat in Alberta-Pacific Forest Management Area
The Alberta Biodiversity Monitoring Institute measured habitat intactness and the human footprint of the Alberta-Pacific Forest Management Area (Al-Pac FMA). This area encompasses 57,331 km2,28 and makes up 9.5% of the Boreal Plains ecozone+.5 Old-forest habitat in the Al-Pac FMA is 92% intact. That is, it occupies 92% of the area that it would be expected to occupy if there were no human impacts. The human footprint index shows that human influence is evident in 7% of the Al-Pac FMA. Most of the human footprint is due to forestry, energy and transportation infrastructure. Half of the forestry footprint was created in the last 10 years.28
Shift from late-succession to early-succession forests
Much of the Canadian landscape was dominated by old forests when European settlement began, although natural disturbance from fires and insects ensured a range of age classes was found across the forested landscape. Old forests have greater structural diversity, complexity, and biodiversity than young forests, but the characteristics of old forests depend on the species and the site history.17, 35 The age at onset of old-growth characteristics varies with disturbance regimes, forest types, and site characteristics.35 For example, in the boreal forest, the age of old–growth stands ranges from about 80 to more than 300 years.36 In Nova Scotia, the government defines old-growth forests as over 125 years of age.35 In the B.C. interior, old-growth forests are defined as 120 to 140 years; on the coast, definitions vary from greater than 140 to greater than 250 years.17, 37, 38 A shift from old to young forests has been observed in some managed forests across the country, such as in the Atlantic Maritime,39 and Boreal Plains.36 In the Newfoundland Boreal40 and Pacific Maritime38 ecozones+ old forests still cover 40% of the forested area and it is assumed that old forests still dominate in the Hudson Plains, where human disturbance is minimal and natural disturbance regimes do not appear to have changed.
Extent of old forests
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