Taiga Shield Ecozone+ Evidence for Key Findings Summary
- Lakes and rivers
- Ice across biomes
National key finding
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.
The northern boundary of the Taiga Shield is defined by the treeline – which is not a sharp line where trees end, but rather a zone of transition from increasingly sparse trees to tundra. The emerging picture for this forest-tundra zone is one of change, but not a uniform expansion of treeline.
West of Hudson Bay
The forest-tundra zone averages 145 km in width in the western Taiga Shield.Footnote21 The presence or absence of trees at points within this transition zone depends on microclimate and topography,Footnote22 as well as on past climatic conditions.Footnote23 An analysis of the treeline zone for Canada west of Hudson Bay (including the treeline zone in the Taiga Plains and Taiga Cordillera ecozones+) shows no net increase in conifers, but significant changes in other land cover types (see box).
East of Hudson Bay
In the Quebec part of the eastern Taiga Shield, trees in the forest-tundra zone have grown faster and taller since the 1970sFootnote24 but distribution of trees has not changed greatly,Footnote25 although white spruce has recently (over the past 50 years) expanded along the east coast of Hudson Bay.Footnote26 In Labrador, treelines have expanded northward and up slopes over the past 50 years along the coast, but not inland.Footnote27
The forest-tundra zone west of Hudson Bay
Mean change over 22 years based on analysis of early spring and summer satellite images. The inset map, adapted from Olthof and Pouliot, 2010,Footnote28 shows the area analysed.
Source: data from Olthof and Pouliot, 2010Footnote28
Long Description for Figure 4.
This graph shows the following information:
|-||Mean percent change|
The inset map depicts the area analysed in the study, which extends along the treeline zone from the northern part of the Yukon across the Northwest Territories and into the southeastern Nunavut/northern Manitoba.
A study using satellite imagery to look at recent trends along the treeline zone west of Hudson Bay found only a small net increase in tree cover, but major changes in vegetation cover (Figure 4).Footnote28 Tree cover increased in the northern half of the zone, but this was mainly offset by decreases in the southern half. The changes were more pronounced to the west of the Taiga Shield, especially west of the Mackenzie Delta, likely related to drier conditions due to the marked warming trends in these regions.Footnote29 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).
National key finding
High loss of wetlands has occurred in southern Canada; loss and degradation continue due to a wide range of stressors. Some wetlands have been or are being restored.
Wetlands cover roughly 13% of the surface area of the Taiga Shield, Footnote18 and trends in the total wetlands area are unknown. Ponds are increasing in parts of Quebec and Manitoba, and probably elsewhere in the Ecozone+ due to melting of frozen peatlands (see Permafrost trends on page 17). This wetland expansion is related to changes in temperature and precipitation patterns. Some reduction of wetlands area has resulted from hydroelectric developments in northern Quebec (see Ecosystem Conversion on page 23). Among the documented changes associated with hydroelectricity development east of James Bay is a reduction in the area of string bogs (narrow, low ridges with wet depressions or pools) in Quebec's Lake Plateau area. These wetlands provide habitat for shorebirds and bald eagles.Footnote30 Both the James Bay (Quebec)Footnote31 and Churchill River (Newfoundland and Labrador)Footnote32 hydro projects will be expanded in the next few years-including development of two substantial reservoirs and diversion of half the flow of the Rupert River-which is likely to have a further impact on wetlands in the eastern Taiga Shield.
Lakes and Rivers
National key finding
Trends over the past 40 years influencing biodiversity in lakes and rivers include seasonal changes in magnitude of stream flows, increases in river and lake temperatures, decreases in lake levels, and habitat loss and fragmentation.
Changes in hydrology on unmanaged streams within the Ecozone+ vary. The streams to the west of the Ecozone+ are part of the Mackenzie River Basin, which has, overall, experienced climate-related increases in streamflow, (1970-2000) while much of the drainage to the east is to Hudson and James bays, which have experienced no net change in total freshwater input (1964-2010). Major changes in the seasonal flow patterns of several rivers, especially those draining to James Bay, have resulted from dams and diversions, starting in 1973.
Large-scale trends relevant to the Taiga Shield Ecozone+ are:
Mackenzie River Basin: increase in annual winter flows and in annual minimum flows from 1970 to 2000, and earlier spring peak flows. Flows in early summer and late fall, as well as the annual mean flow, decreased slightly. The trends correlate with warmer winters and springs, less winter snow, and more spring rain.Footnote33 Hudson Bay watershed: discharge declined from the mid-1960s to the mid-1980s, followed by a period of relatively high flows and an upward trend (Figure 5). It is unclear to what degree these trends are related to climate change and/or decadal climate oscillations.Footnote34 While there was no trend in total discharge over the entire period, streamflow increased in the winter and decreased in the summer from 1964 to 2008. This seasonal shift is attributed to the strong influence of increasing flow regulation in this watershed: water stored in spring and summer is released in the winter for power generation.Footnote34
Total discharge is estimated based on records from 23 rivers, including the regulated La Grande Rivière.
Source: Déry et al., 2011Footnote34 with 2009 and 2010 data provided by S.J. Déry
Long Description for Figure 5.
This line graph shows the following information:
|Year||Total discharge (km3)|
Trends within the ecozone+: streams with natural flow regimes
This section is based on Canada-wide analyses performed by Cannon et al. 2011Footnote35 for the 2010 Ecosystem Status and Trends Report.
Within both eastern and western parts of the Taiga Shield, hydrometric records are sparse and often too short to detect trends. Only two stations (Camsell River, NWT, and Seal River, Manitoba) – both in the western Taiga Shield – have adequate stream discharge and climate records (1961-2003) to examine trends over the annual cycle.Footnote35 Both of these streams showed significant streamflow increases throughout the year, with the exception of spring (streamflow for Camsell River is shown in Figure 6). These changes could be due to a combination of the increased precipitation coupled with the warmer winters and springs recorded in the vicinity of the streams.Footnote35
Trends within the ecozone+: streams with managed flow regimes
Several major hydroelectricity developments, mainly in the eastern part of the ecozone+, have altered flow regimes since the 1970s. The La Grande (James Bay) hydroelectric development in Quebec has resulted in dramatic changes to some rivers in the eastern Taiga Shield. The complex was constructed in two phases, the first one during 1973-1985 and the second one during 1987-1996. Three main rivers were diverted into La Grande River: the Eastmain, Opinaca, and Caniapiscau. As a result of these diversions, the mean annual flow of La Grande River at its mouth doubled and its mean winter flow increased more than tenfold.Footnote30
Main impacts from these diversions include changes to estuarine, coastal and marine systems from the increased under-ice freshwater plume of La Grande RiverFootnote36 (see Coastal on page 15).
Fishing yields fluctuated after diversions were put in place, but, overall, yields stabilized at levels above or close to those found under natural conditions.Footnote37 In general, fish species composition and growth rates in the reduced-flow rivers were similar before and after the flow reductions.
Changes to fish populations in rivers with altered flow include:
- La Grande River: displacement of species that are not tolerant of cold water – walleye (Sander viterus) and cisco (Coregonus sp.) – by cold-water tolerant species – round whitefish (Prosopium cylindraceum) and brook trout (Salvelinus fontinalis).Footnote37 Mean maximum summer water temperatures in the river were lowered from 16°C to 8°C following development.Footnote37
- Eastmain River: lake sturgeon (Acipenser fulvescens) numbers declined, related to flow reduction and habitat fragmentation by weirs.Footnote37, Footnote38 Fishing pressure may also have been a factor in this decline.Footnote37, Footnote38 The James Bay population of lake sturgeon was assessed as being of Special Concern by COSEWIC in 2005, confirmed in 2006,Footnote38 citing declines in habitat and possibly abundance, related to existing and projected hydroelectric development.
Changes affecting fish in the reservoirs are discussed under Dams and reservoirs on page 28.
National key finding
Coastal ecosystems, such as estuaries, salt marshes, and mud flats, are believed to be healthy in less-developed coastal areas, although there are exceptions. In developed areas, extent and quality of coastal ecosystems are declining as a result of habitat modification, erosion, and sea-level rise.
The eastern Taiga Shield Ecozone+ has coastlines along James and Hudson Bays, Ungava Bay, and the Atlantic Ocean. Little information on status and trends in coastal ecosystems was found for this report. The James and Hudson bays region is undergoing a high rate of isostatic rebound, meaning that new soil and vegetation zones are forming. Eelgrass beds, formerly extensive along the James Bay coast, declined rapidly in the late 1990s, recovering somewhat to 2011. Footnote39
A severe reduction in eelgrass (Zostera marina) along the James Bay coast was reported by Cree residents of the region in 1998; this decline was also detected in monitoring conducted by Hydro Québec. Footnote40 By 2004, monitoring indicated that some recovery had taken place, confirmed by further monitoring in 2009 (Figure 7)Footnote41 and 2011. Footnote39
Eelgrass beds were among the most extensive in North America, distributed all along the east coast of James Bay, covering 250 km2, and found at depths of 0.5 to 4 mFootnote42 prior to their rapid decline in density and biomass around 1998 (Figure 7). Eelgrass in James Bay provides shelter for small fish and invertebrates and is important food and habitat for migrating and wintering waterfowl, Canada geese (Branta canadensis) and Brant geese (Branta bernicla) in particular, and provides foraging areas for Arctic terns.Footnote43 Footnote44 Footnote45 Eelgrass distribution and growth are influenced by salinity;Footnote45 low salinity or high temperatures can make eelgrass vulnerable to disease.Footnote43
Samples were taken at several depths at 6 sites – this figure shows results typical at all depths for 5 of the 6 sites. The 6th site (Dead Duck Bay, the station furthest to the south of the La Grande River mouth) showed no change.
Source: GENIVAR, 2009Footnote41
Long Description for Figure 7.
Three bar graphs showing the following information:
|Year||Mean dry biomass (g/m2)||Mean number of shoots (N/m2)|
|Year||Mean dry biomass (g/m2)||Mean number of shoots (N/m2)|
|Year||Mean dry biomass (g/m2)||Mean number of shoots (N/m2)|
Explanations advanced for the decline include:
- a disease outbreak triggered by unusually high summer and winter temperatures, along with changes in the coast from isostatic rebound and other changes related to a warming climate;Footnote40
- impaired growth and survival due to reduced salinity of water in James Bay resulting from larger and more frequent discharges of fresh water via the La Grande River (due to diversions, see Dams and diversions, page 25).Footnote45
As of 2011, vast eelgrass beds can be seen at various locations along James Bay. Distribution and abundance of eelgrass has not recovered to pre-decline levels, however, and recovery is not uniform along the coast.Footnote39
Ice across biomes
National key finding
Declining extent and thickness of sea ice, warming and thawing of permafrost, accelerating loss of glacier mass, and shortening of lake-ice seasons are detected across Canada's biomes. Impacts, apparent now in some areas and likely to spread, include effects on species and food webs.
Lake ice trends
An analysis of seven large lakes in or at the edges of the ecozone+, between 1970 and 2004, showed variable trends in timing of freeze-up and ice break-up, with few changes being statistically significant.Footnote46 National trends are towards an earlier break-up of lake ice, with less consistent trends in freeze-up timing (1960s or 1970s to 1990s, when most lake ice monitoring was discontinued).Footnote17
Permafrost is thawing at a rapid rate in the eastern Taiga Shield, resulting in a change in the landscape from dry, lichen-heath ecosystems supporting black spruce trees and dotted with ponds to wetter landscapes with ponds, and characterized by fen and bog vegetation.Footnote47-Footnote49 As well as altering habitats, these changes affect carbon flux as the thawing of peat and formation of ponds releases carbon to the atmosphere, while the subsequent transition to fen/bog vegetation stores carbon. Permafrost is also degrading in peatlands in northern Manitoba (based on field investigations over the latter half of the 20th century).Footnote50 This trend is likely becoming more widespread in the western Taiga Shield as well, although data are not available.
Broad-scale permafrost distribution in the Taiga Shield ecozone+ differs between east and west of Hudson Bay, with the east having less extensive permafrost (Figure 8). In the eastern Taiga Shield, the sporadic permafrost zone is characterized by frozen peat plateaus and palsas (mounds of peat or soil containing ice lenses). Formation and degradation of these permafrost landforms are influenced by air temperature and by insulation from snow cover and from peat.Footnote47 When the permafrost is degraded, the resulting melted ice forms ponds (called thermokarst ponds).
Three studies in Quebec show the extent of change in permafrost in the past 50 years (summarized in Figure 9).
- A study mapping palsas and thermokarst ponds along the Boniface River in the discontinuous permafrost zone at the northern edge of the ecozone+ (site A, Figure 9)Footnote47 found that the area occupied by palsas decreased by 23% between 1957 and 2001, while 76% of present-day thermokarst pond area had formed since 1957. No new palsas developed along the river during this period. Permafrost degradation was most severe close to the river where water fluctuations had a strong influence.
- A study mapping change in a peatland east of Hudson Bay (site B, Figure 9)Footnote48 found that the area was mainly frozen in 1957, with about 18% of the surface covered in thermokarst ponds. Palsa mounds, being well-drained, supported growth of lichens and black spruce trees. By 2003 only 13% of the surface area remained as permafrost, with the remainder being a mix of thermokarst ponds and fen/bog vegetation (sedges and Sphagnum moss). Fen/bog vegetation was virtually absent in 1957 but covered half the study area by 2003. Spruce trees died as the permafrost decayed and their roots became flooded. The annual rate of permafrost degradation approximately doubled in the last decade of the study to -5.3% per year; this acceleration in melt rate was likely related to increasing trends in summer temperatures and precipitation since the mid-1990s.
- A survey over a broad area of the James Bay regionFootnote49 showed that changes documented at the above sites are widespread. The landscape in the zone of sporadic permafrost is in transition from dry, lichen-covered palsas interspersed with ponds to a wetter ecosystem dominated by larger ponds, bogs and fens. The southern limit of permafrost has moved about 130 km north, mainly within about the past 50 years. North of the current permafrost boundary (in the vicinity of "C" on Figure 9), permafrost is in an advanced state of degradation – palsas in bogs observed and surveyed in this region up to 2004 had shrunk or disappeared by 2005.
Lichens, important forage for caribou (Rangifer tarandus), are maintained in the James Bay area by periodic fire and by permafrost – both of which create dry micro-environments. If, as seems likely, the permafrost continues to degrade and disappears within a few years, the resulting wetter bog ecosystems will lead to widespread declines in lichen.Footnote49
Studies A and B are based on ground surveys and 1957 air photos.
Study C involved helicopter surveys along two 350 km north-south transects conducted in 2004 and 2005. These were supplemented with ground surveys, defined the northern extent of permafrost by the presence of palsas and the southern extent of thermokarst ponds (the latter indicating the presence of permafrost within about the past 50 years). "C" indicates the approximate location of palsa/thermokarst pond study sites.
Source: Study A. Vallée and Payette, 2007;Footnote47 Study B. Payette et al., 2004;Footnote48 and Study C. Thibault and Payette, 2009Footnote49
Long Description for Figure 9.
This figure includes a map and two graphs documenting changes in the total area, land cover, and permafrost limits in three studies from northern Quebec. The bar graph on the top left depicts a 23% decrease in the total area of palsas (mounds of peat or soil containing ice lenses) and a 76% increase in pond area between 1957 and 2001; the location of the study site is indicated on the map at point "A", along the Boniface River. The line graph on the top right shows the following information:
In addition to showing the locations of the three studies, the map at the bottom also depicts a 130 km northward change in the southern permafrost limit, documented in a more recent study (study "C", 2004 and 2005), which defined the southern extent of areas which were formerly permafrost by the presence of thermokarst ponds.
- Footnote 11
Smith, S. 2011. Trends in permafrost conditions and ecology in Northern Canada. Canadian Biodiversity: Ecosystem Status and Trends 2010, Technical Thematic Report No. 9. Canadian Councils of Resource Ministers. Ottawa, ON. iii + 22 p.
- Footnote 17
Monk, W.A. and Baird, D.J. 2011. Biodiversity in Canadian lakes and rivers. Canadian Biodiversity: Ecosystem Status and Trends 2010, Technical Thematic Report No. 19. Canadian Councils of Resource Ministers. Ottawa, ON. Draft report.
- Footnote 18
Wiken, E., Moore, H. and Latsch, C. 2004. Peatland and wetland protected areas in Canada. Wildlife Habitat Canada Science Report. Wildlife Habitat Canada. Ottawa, ON. 18 p.
- Footnote 21
Timoney, K.P., Roi, G.H.L., Zoltai, S.C. and Robinson, A.G. 1992. The high Subarctic forest-tundra of northwestern Canada: position, width, and vegetation gradients in relation to climate. Arctic45:1-9.
- Footnote 22
Timoney, K.P. 1995. Tree and tundra cover anomalies in the Subarctic forest-tundra of northwestern Canada. Arctic48:13-21.
- Footnote 23
Nichols, H. 1976. Historical aspects of the northern Canadian treeline. Arctic29:38-47.
- Footnote 24
Gamache, I. and Payette, S. 2004. Height growth response of tree line black spruce to recent climate warming across the forest-tundra of eastern Canada. Journal of Ecology92:835-845.
- Footnote 25
Gamache, I. and Payette, S. 2005. Latitudinal response of Subarctic tree lines to recent climate change in eastern Canada. Journal of Biogeography32:849-862.
- Footnote 26
Laliberte, A.C. and Payette, S. 2008. Primary succession of Subarctic vegetation and soil on the fast-rising coast of eastern Hudson Bay, Canada. Journal of Biogeography35:1989-1999.
- Footnote 27
Payette, S. 2007. Contrasted dynamics of northern Labrador tree lines caused by climate change and migrational lag. Ecology88:770-780.
- Footnote 28
Olthof, I. and Pouliot, D. 2010. Treeline vegetation composition and change in Canada's western Subarctic from AVHRR and canopy reflectance modeling. Remote Sensing of Environment114:805-815.
- Footnote 29
Pisaric, M.F.J., Carey, S.K., Kokelj, S.V. and Youngblut, D. 2007. Anomalous 20th century tree growth, Mackenzie Delta, Northwest Territories, Canada. Geophysical Research Letters34, L05714, 5 p..
- Footnote 30
Hayeur, G. 2001. Summary of knowledge acquired in northern environments from 1970 to 2000. Hydro-Québec. Montréal, QC. x + 110 p. .
- Footnote 31
Hydro-Québec. 2010. Eastmain-1-A/Sarcelle/Rupert project [online]. Hydro-Québec. (accessed December, 2010).
- Footnote 32
Nalcor Energy and Government of Newfoundland and Labrador. 2011. Report of the Joint Review Panel -- Lower Churchill hydroelectric generation project. Government of Canada and Government of Newfoundland and Labrador. Ottawa, ON and St. John's, NL. 355 p.
- Footnote 33
Abdul Aziz, O.I. and Burn, D.H. 2006. Trends and variability in the hydrological regime of the Mackenzie River Basin. Journal of Hydrology319:282-294.
- Footnote 34
Déry, S.J., Mlynowski, T.J., Hernández-Henríquez, M.A. and Straneo, F. 2011. Interannual variability and interdecadal trends in Hudson Bay streamflow. Journal of Marine Systems88:341-351-.
- Footnote 35
Cannon, A., Lai, T. and Whitfield, P. 2011. Climate-driven trends in Canadian streamflow, 1961-2003. Canadian Biodiversity: Ecosystem Status and Trends 2010, Technical Thematic Report No. 19. Canadian Councils of Resource Ministers. Ottawa, ON. Draft report.
- Footnote 36
Hydro-Québec and GENIVAR Groupe Conseil inc. 2005. Environmental monitoring of the La Grande-2-A and La Grande-1 projects: abridged summary report 1987-2000: La Grande Rivière winter plume. Joint report by Hydro-Québec and GENIVAR Groupe Conseil Inc. 27 p. + appendix.
- Footnote 37
Therrien, J., Verdon, R. and Lalumière, R. 2004. Environmental monitoring at the La Grande complex. Changes in fish communities. Summary report 1977-2000. GENIVAR Groupe Conseil Inc. and Direction Barrages et Environnement, Hydro-Québec Production. 129 p. + appendices.
- Footnote 38
COSEWIC. 2006. COSEWIC assessment and update status report on the lake sturgeon Acipenser fulvescens in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa, ON. xi + 107 p.
- Footnote 39
Consortium Waska-GENIVAR. 2011. Centrales de l'Eastmain-1-A et de la Sarcelle et dérivation Rupert. Suivi de la zostère marine de la côte nord-est de la baie James. Rapport d'étude 2011. Rapport du Consortium Waska-GENIVAR inc. pour Hydro-Québec Production. 57 p. + appendices.
- Footnote 40
Hydro-Québec and GENIVAR Groupe Conseil inc. 2005. Environmental monitoring at the La Grande complex: abridged summary report 1988-2000: eelgrass meadows of the northeast coast of James Bay. Joint report by Hydro-Québec and GENIVAR Groupe Conseil Inc. 42 p. + appendices.
- Footnote 41
GENIVAR. 2010. Centrales de l'Eastmain-1-A et de la Sarcelle et dérivation Rupert. Suivi de la zostère marine de la côte nord-est de la baie James. État de référence 2009. Rapport de GENIVAR Société en commandite pour Hydro-Québec et la Société d'énergie de la Baie James. 54 p. + appendices.
- Footnote 42
Lalumière, R., Messier, D., Fournier, J.J. and Mcroy, C.P. 1994. Eelgrass meadows in a low Arctic environment, the northeast coast of James Bay, Quebec. Aquatic Botany47:303-315.
- Footnote 43
Standing Committee on Fisheries and Oceans. 2008. Fifth report of the Standing Committee on Fisheries and Oceans to the House of Commons. Government of Canada. Ottawa, ON. 2 p.
- Footnote 44
Hanson, A.R. 2004. Status and conservation of eelgrass (Zostera marina) in eastern Canada. Technical Report Series No. 412. Environment Canada, Canadian Wildlife Service, Atlantic Region. Sackville, NB. 40 p.
- Footnote 45
Short, F.T. 2008. Report to the Cree Nation of Chisasibi on the status of eelgrass in James Bay. Jackson Estuarine Laboratory. Durham, NH. 30 p.
- Footnote 46
Latifovic, R. and Pouliot, D. 2007. Analysis of climate change impacts on lake ice phenology in Canada using the historical satellite record. Remote Sensing of Environment106:492-507.
- Footnote 47
Vallée, S. and Payette, S. 2007. Collapse of permafrost mounds along a Subarctic river over the last 100 years (northern Québec). Geomorphology90:162-170.
- Footnote 48
Payette, S., Delwaide, A., Caccianiga, M. and Beauchemin, M. 2004. Accelerated thawing of Subarctic peatland permafrost over the last 50 years. Geophysical Research Letters31:1-4.
- Footnote 49
Thibault, S. and Payette, S. 2009. Recent permafrost degradation in bogs of the James Bay area, northern Quebec, Canada. Permafrost and Periglacial Processes20:383-389.
- Footnote 50
Camill, P. 2005. Permafrost thaw accelerates in boreal peatlands during late-20th century climate warming. Climatic Change 68:135-152.
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