Forests

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Photo: boreal forest © Canadian Forest Service


Boreal Forest

Deforestation

Area (km2)
Graph: deforestation. Click for graphic description (new window).
Long Description for deforestation

This bar chart shows area of deforestation from 1990 to 2007. The area deforested annually declined from approximately 700 square kilometres in 1990 to approximately 500 square kilometres in 1994. After 1994, annual deforestation remained stable at this level, with the exceptions of 1995 and 2006 when annual deforestation was 800 square kilometres and 750 square kilometres respectively.

 

Note: This graph depicts deforestation – the area of forest converted to other land cover types. As it does not include the area converted from other land types to forests, it is not a depiction of net change in forest area.
Source: adapted from Environment Canada, 200913 and Natural Resources Canada, 200814

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

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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

Vegetation changes in the treeline zone of western Canada
1985 to 2006
Graph: vegetation changes in the treeline zone. Click for graphic description (new window).
Long Description for Vegetation changes in the treeline zone of western Canada

This bar chart shows the percent change in the amounts of different classes of vegetation in the treeline zone west of Hudson Bay from 1985 to 2006. Over this period, bare land decreased by 9.4%, lichen cover decreased by 3.9%, conifer cover increased by 0.45%, herb cover increased by 12%, and shrub cover increased by 15%. An inset map shows the location of the treeline zone analyzed in this study. It is a broad band along the southern boundary of the Arctic Ecozone+ from west of Hudson Bay to the Yukon-Alaska border.

 

Mean change across the zone over 22 years based on analysis of early spring and summer satellite images.
Source: data from Olthof and Pouliot, 201023

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

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Photo: Gros Morne National Park, Newfoundland and Labrador © iStock.com/Mmac72
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

Map: Intactness of Canada's landscapes. Click for graphic description (new window).
Long Description for Intactness of Canada's landscapes

This map of Canada has ecozone+ boundaries marked on it and uses colour coding to divide the land area into two classes: first, intact landscapes free of human disturbance, defined as intact blocks greater than 50 square kilometres for the boreal forest and greater than 10 square kilometres for the temperate forest; and, second, landscapes that are fragmented by human disturbance. Fragmented landscapes dominate the southern part of Canada, extending further north in some places, especially in the Boreal Plains and Montane Cordillera ecozones+. A region of intact landscape is apparent along the Rocky Mountains. The Arctic Ecozone+ was excluded from this analysis.

 

Note: Intact landscapes are defined as >50 km2, for the boreal forest,and >10 km2 for the temperate forest.
Sources: adapted from Lee et al., 201027

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

Percent intact
Graph: intactness of old forest habitat in Alberta-Pacific Forest Management Area. Click for graphic description (new window).
Long Description for Intactness of old forest habitat in Alberta-Pacific Forest Management Area

This graph shows the percent of intact old-forest habitat in the Alberta-Pacific Forest Management Area. The total area of intact old-forest habitat is 92%. This analysis is also broken down by forest type as follows: 93% of white spruce and fir, 95% of pine, 91% of deciduous, and 93% of mixedwood old forest habitats are classified as intact.

 

 
Source: adapted from Alberta Biodiversity Monitoring Institute, 200928
 

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

 

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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

Map and graphs: extent of old forests in various locations in Canada. Click for graphic description (new window).
Long Description for Extent of old forests

This graphic shows the percent of old forest for locations throughout Canada over a range of time periods. A separate bar chart is shown for each of five locations. These locations are shown on a map of Canada. Overall, the charts show a shift to younger forests, except in the Quebec portion of the Mixedwood Plains.

Each graph is described in the following set of points:

  1. Alberta’s boreal forests. The percent of forests greater than 120 years old declined from 29% in 1991 to 18% in 1999.
  2. Newfoundland Boreal Ecozone+. In 2009 the percent of young forest was 59% and the percent of forest older than 81 years was 41%.
  3. Nova Scotia. The percent of forests greater than 100 years old decreased from 8.7% in 1958 to 0.3% in the period 1997 to 2003. The percent of forests between 81 and 100 years old decreased from 16% to 1.2% over the same timeframe.
  4. Quebec portion of the Mixedwood Plains Ecozone+. Forest age structure over three time periods (1969 to 1975; 1981 to 1988; and 1990 to 1995) is compared. The percent of regenerating forest (less than 2 metres tall) and young forest (taller than 7 metres with increasing growth) remained relatively constant at approximately 10% and 45% respectively, while the percent of regenerated forest (2 to 7 metres tall) declined from approximately 25% to 10%. The proportion of mature and senescent forest (taller than 7 metres with stable or decreasing growth) increased over the period from approximately 18% to 32%.
  5. Coastal B.C. The percent of forest older than 140 years decreased from approximately 62% before European contact to 41% in the mid 1990s.

 

Note: age and size class distributions are affected by both natural and human disturbances.
Sources (clockwise, starting with Alberta): Timoney, 2003,36 Newfoundland and Labrador Department of Natural Resources, 2009,40 Pannozza and Coleman, 2008,39 Ministère des Ressources naturelles et Faune du Quebec, 2010,41 B.C. Ministry of Environment, 200638

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