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Theme: Habitat, wildlife, and ecosystem processes

Intact landscapes and waterscapes

National key finding
Large tracts of relatively intact natural landscapes and waterscapes, where ecosystem processes are either known or presumed to be functioning properly, are found in many areas, but particularly in the north and west. This includes globally and nationally significant terrestrial, freshwater and marine movement corridors.

Evidence from Ontario

Landscapes

Due to the high level of fragmentation found in the Mixedwood Plains Ecozone+, areas of intact natural cover (landscapes and waterscapes) are quite small.  In Ontario, the percentage of natural vegetation cover found in the ecozone+ ranges from a low of 18% in the Southwest, to a high of 57% in the Frontenac Arch and 51% in the Escarpment. The Eastern and Central physiographic areas have 37 and 35% natural vegetation respectively (Figure 29).161

Figure 29. Percentage cover of natural vegetation in the Ontario portion of the Mixedwood Plains Ecozone+. Represents all natural ecosystems (forest, wetlands, prairie savannah, etc.) found in the Ontario Portion of the Mixedwood Plains Ecozone+ by physiographic zone.
Map and bar graph of Ontario
Long description for Figure 29

This figure contains a stacked bar graph and a map. The map shows the five broad physiographic regions of the Ontario portion of the ecozone+. These are the Escarpment, a narrow strip which extends from Niagara Falls to the northern tip of the Bruce Peninsula, and to Manitoulin Island. The South West region encompasses all of the ecozone+ to the west of the Escarpment. The Central region ranges from east of the Escarpment to the Frontenac Arch, which separates the Great Lakes lowlands from the St. Lawrence River lowlands. The remaining area to the east of the Frontenac Arch is the Eastern physiographic region.

The stacked bar graph shows the following information:
Physiographic RegionUpland forestSwampOpen wetlandRare communities
South West8910
Escarpment43610
Central181530
Frontenac Arch421040
Eastern171820

Source: Ontario Ministry of Natural Resources, 2010161

When the patch size distribution of forested lands within the Ontario portion of the ecozone+ was examined, the Escarpment and Frontenac Arch had 41 and 40% in patches greater than   200 ha, the Central and Eastern zones had 21 and 24% of their forest in patches greater than   200 ha, while only 5% of Southwestern Ontario had forest patches greater than 200 ha (Figure 30).161 When forest patch sizes are over 200 ha, research has shown that, generally, 80% of area-sensitive bird species find suitable habitat, however, when the forest patches are under 75 ha, they tend to be dominated by forest edge species.189 Habitat for area sensitive forest bird species in Southwestern Ontario is severely limited in its supply.  In addition, if upland forest is required for habitat, the situation is even more limited as there is only 1% cover of upland forest in Southwestern Ontario in patch size greater than 200 ha.161 When Global Forest Watch323 examined the Mixedwood Plains Ecozone+they found that it had no area which fitted their definition of intact forest landscape (forest patches which were a minimum of 5,000 ha), however they did find 1.5% of the ecozone+had forest patches which ranged from 1,000 ha to less than 5,000 ha.  As forest cover is converted to other uses such as agriculture and urban lands, impacts can occur to stream ecosystems.324 Several studies in this ecozone+ have demonstrated that sensitive fish and macrobenthic invertebrate species are no longer found when development in upstream catchments exceeds a fairly low threshold. This effect can occur with as much as 50% forest cover still remaining.100

Figure 30. Percentage of forested lands in Ontario portion of the ecozone+ with patches <75 ha, ≥75 and <200 ha, and ≥200 ha).
Map and bar graph of Ontario.
Long description for Figure 30

La carte indique les cinq vastes régions physiographiques de la partie ontarienne de l’écozone+. Il s’agit de l’escarpement, une bande étroite qui s’étend de Niagara Falls jusqu’à la pointe nord de la péninsule Bruce, et jusqu’à l’île Manitoulin. La région sud-ouest comprend l’ensemble de l’écozone+ située à l’ouest de l’escarpement. La région centrale s’étend de l’escarpement à l’arche de Frontenac, qui sépare les basses terres des Grands Lacs et celles du fleuve Saint-Laurent. La région restante à l’est de l’arche de Frontenac est la région physiographique de l’est.

The stacked bar graph shows the following information:
Percent of total land area
Physiographic Region≥ 75 ha and <200 ha<75 ha≥ 200ha
South West384
Escarpment2641
Central3821
Frontenac Arch4740
Eastern3823

Source: Ontario Ministry of Natural Resources, 2010161

The negative impact of roads on wildlife and ecosystems has been recognized as a major contributor to the global biodiversity crisis for many species.325,326,327,328 Thus, examining how “roaded” a landscape is provides another way to examine its level of intactness.329 The most densely roaded area of the Ontario portion of the ecozone+ is the Central physiographic area which has an average road density of 1.89 km/km2 while the Frontenac Arch has the lowest average road density at 1.14 km/km2. The vast majority of these roads within the ecozone+ are main thoroughfares and concession roads (Table 10).

Table 10. Road density by physiographic zone.
Physiographic RegionHighways (km/km2)Main Thoroughfares and Concession roads (km/km2)Local Streets (km/km2)Total by Physiographic Region (km/km2)
Central0.151.090.651.89
Escarpment0.120.880.491.49
South West0.091.050.271.41
Eastern0.100.920.331.35
Frontenac Arch0.110.920.111.14
Entire Mixedwood plains0.111.020.401.53

Source: Ontario Ministry of Natural Resources, 2009330

When the amount of natural vegetation in patches greater than 200ha in size within the Ontario portion of the ecozone+was assessed to determine how much was >100 m, >500 m, and >1000 m from a road, it was found that 45% of the existing natural vegetation occurred in patches larger than 200 ha more than 100 m from a road. At more than 1 km from a road, only 10% of the existing natural vegetation is found in patches greater than 200 ha. When broken down by physiographic area, the Escarpment had the greatest percentage of natural vegetation cover (27%) in patches over 200 ha more than 1 km from a road , followed by the Frontenac Arch at 14%, the Eastern and Central physiographic zones at 8 and 5%, and the Southwest had only 2% (Table 11).330

Table 11. Natural vegetation in Ontario portion of Mixedwood Plains Ecozone+. Amount of Natural Vegetation (forests, wetlands, prairie-all natural ecosystem types) and patches ≥200ha found at >100m. >500m and >1000m from a road in the Ontario Portion of the Ecozone+.
Physiographic RegionPercent of Land Area in Natural CoverPercent Natural cover in patches>=200haPercent of Natural cover >100m from roadsPercent Natural cover in Patches >=200ha that are >100m from roadsPercent of Total Natural cover >500m from roadsPercent Natural Cover in patches>200ha in size>500m from roadsPercentage of Total Natural Cover >1000m from roadsPercentage Natural Cover in patches >=200ha in size >1000m from roads.
Central35%68%85%43%35%19%8%5%
Eastern37%74%88%53%43%28%12%8%
Escarpment51%84%89%68%54%45%30%27%
Frontenac Arch57%83%87%64%47%35%19%14%
South West18%33%86%18%35%6%4%2%
Total Ontario Mixedwood Plains30%64%87%45%41%23%13%10%

Source: Ontario Ministry of Natural Resources, 2009330

When examined spatially, it can be seen (Figure 31) that the majority of 200 ha patches in the Escarpment are found on Manitoulin Island and at the north end of the Bruce Peninsula, while at the southern end of the Escarpment there are no 200 ha patches more than 1 km from a road. The Southwest zone has very few patches more than 1 km from a road, the majority of which are located on Walpole Island. There are a few other widely scattered locations such as west of Chepstow and west of Badjeros. 

Figure 31. Proximity of large natural patches from roads in the Ontario portion of the Mixedwood Plains ecozone+.
Map of Ontario
Long description for Figure 31

This map shows the distribution of large natural patches (woodlands and wetlands) greater than 200 hectares in size in the Ontario portion of the Mixedwood Plains Ecozone+. The three categories identified are: more than 1km from a road; more than 500m from a road; and more than 100 m from a road. Most of these natural patches are scattered along the northern part of the region from Manitoulin Island and the Bruce Peninsula eastward. Most are within 500m of a road, but a there are a few patches which are more than 1km from a road, mainly on Manitoulin Island and the Bruce Peninsula, but also west of Lake Simcoe and northeast of the Kwartha Lakes. Very little of the southwest part of the region has large natural patches.

The impact of roads varies greatly depending on the species in question, and the size and traffic level of the road. When roads are built, not only is natural cover lost, but roads can also act as barriers to movement and are often large sources of mortality.331 Four lane highways have been found to impact moose corridors, grassland bird habitat usage, and cause road salt damage to distances up to 1 km.332 When frog populations were studied along Hwy 401 (a four or more lane major highway), it was found that species richness was impacted to a distance of 450 to 800 m away with chorus frog populations being impacted to distances of 100 to 2400 m.325 Conversely, studies of logging roads, have shown impacts on plant species composition extending no more than 15 m from the road.333 

Waterscapes

Fragmentation of aquatic systems with dams, weirs, and other barriers is a significant global biodiversity issue.116,334,335 The impacts of barriers on the movement of aquatic species causes loss of species diversity and ecosystem structure.116,335,336 In a global overview of dam-based impacts of large river systems, the entire Mixedwood Plains Ecozone was found to be highly impacted.116 When barriers to movement were examined in five watersheds in Central physiographic region of Ontario, it could be seen that all five had barriers to aquatic species movement, however, there were large differences in the amount of fragmentation seen between watersheds. Wilmot and Oshawa creeks have relatively few barriers along their main channels, with Wilmot having the least number of barriers, while the Ganaraska River, Cobourg Creek, and Duffins Creek all have numerous barriers in their catchments making natural species movement very difficult (Figure 32). Though causal relationships cannot be drawn between barriers and productivity at this time, Wilmot Creek is recognized as the most productive cold-water stream running into Lake Ontario.337,338

Figure 32. Extent of barriers to fish movement in five creek catchments in southern Ontario.
Map of southern Ontario
Long description for Figure 32

This map shows the distribution of barriers and perched culverts in the Duffins Creek, Oshawa Creek, Wilmot Creek, Ganaraska River and Cobourg Creek catchments. For Duffins Creek, the barriers are most concentrated on the east side of the catchment with others scattered throughout. The barriers in the Oshawa Creek catchment are sparsely scattered in the northwest section. The Wilmot creek catchment has a light scattering of barriers in the south and west. The Ganaraska River catchment has more numerous barriers scattered throughout, and the Cobourg Creek catchment has a heavier concentration of barriers in the north.

Source: Ontario Ministry of Natural Resources, 2010339

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Key finding 16
Agricultural landscapes as habitat

National key finding
The potential capacity of agricultural landscapes to support wildlife in Canada has declined over the past 20 years, largely due to the intensification of agriculture and the loss of natural and semi-natural land cover.

Agricultural land is the dominant land cover type in the Mixedwood Plains making up over 60% of the ecozone+.8,340 Agricultural land use has been linked to species endangerment in the Mixedwood Plains Ecozone+.341 A total of 355 terrestrial vertebrate species (birds 252, mammals 58, reptiles 24, and amphibians 21) use this agricultural land.  With so much of the ecozone+ in agricultural land cover, the ability of that land to support wildlife is essential in preserving the biodiversity of the ecozone+.

When an index of wildlife habitat capacity of the agricultural land in the Mixedwood Plains was examined for the time period between 1986 and 2006, it was found to have declined significantly340 throughout the ecozone+ (a change from moderate to low capacity).340 Over the time period, habitat capacity decreased on 35.5% of agricultural land, increased on 19.9%, and was constant on 44.6% (Figure 33). This change was due in large part to the decrease in pasture and “all other land” (largely woodland and wetland) by 37.6 and 4.8% respectively.340

Figure 33. Changes in wildlife habitat capacity on agricultural land in the Mixedwood Plains Ecozone+ between 1986 and 2006. ANOVA, Tukey HSD p<0.05.
Map of southern Ontario
Long description for Figure 33

This map shows the extent and location of changes in wildlife habitat capacity in the ecozone+. The ecozone+ is divided into four regions: Lake Erie Lowland, encompassing the area north of lake Erie from Port Franks to Toronto; Manitoulin-Lake Simcoe, which covers the remainder of the ecozone+ west of the Frontenac Arch; the Frontenac Axis, which corresponds to the Frontenac Arch described in Figures 32 and 33; and the St. Lawrence Lowlands, which cover the ecozone+ east of the Frontenac Axis.

For most of the Lake Erie Lowlands, habitat capacity remained constant or increased, with the exception of areas around London, Hamilton and Toronto, and along the south edge of the Niagara Peninsula. For Manitoulin-Lake Simcoe, habitat capacity decreased throughout the majority of the area, including all of the Bruce Peninsula and most of Manitoulin Island. There were also significant areas of decreased habitat capacity around Lake Simcoe and the Kawartha Lakes. Capacity remained constant in patches throughout the region and increased in a few small areas, including the north edge of the Niagara Peninsula, the area east of Toronto and in Prince Edward County. Habitat capacity decreased in almost the entire Frontenac Axis, with the exception of a small strip along the edge of Lake Ontario, where it remained constant. In the St. Lawrence Lowlands, large patches of decreased habitat capacity are found in the areas around Ottawa and Montreal, along the American border between those two cities, and southeast of Lac Saint-Pierre. The St. Lawrence Lowlands also has the highest percentage of areas with increased habitat capacity in the ecozone+.

For most of the Lake Erie Lowlands, habitat capacity remained constant or increased, with the exception of areas around London, Hamilton and Toronto, and along the south edge of the Niagara Peninsula. For Manitoulin-Lake Simcoe, habitat capacity decreased throughout the majority of the area, including all of the Bruce Peninsula and most of Manitoulin Island. There were also significant areas of decreased habitat capacity around Lake Simcoe and the Kawartha Lakes. Capacity remained constant in patches throughout the region and increased in a few small areas, including the north edge of the Niagara Peninsula, the area east of Toronto and in Prince Edward County. Habitat capacity decreased in almost the entire Frontenac Axis, with the exception of a small strip along the edge of Lake Ontario, where it remained constant. In the St. Lawrence Lowlands, large patches of decreased habitat capacity are found in the areas around Ottawa and Montreal, along the American border between those two cities, and southeast of Lac Saint-Pierre. The St. Lawrence Lowlands also has the highest percentage of areas with increased habitat capacity in the ecozone+.

Source: Javorek and Grant, 2011340

During the study period, the amount of cropland expanded from 65 to 72% of the total amount of agricultural land. This represents an intensification of agriculture based primarily on the substantial increase in soybean production (6 to 16%).340 The changes in wildlife habitat capacity are presented in Figure 34.340

Figure 34. Wildlife habitat capacity on agricultural land in the Mixedwood Plains in 1986 (top) and 2006 (bottom).
Two maps of southern Ontario
Long description for Figure 34

These two maps show the wildlife habitat capacity on agricultural ground in the ecozone+ in 1986 and 2006. Categories of habitat capacity are Very Low (<20-30); Low (30-50); Moderate (50-70); High (70-90); and Very High (90->100).

The 1986 map shows that overall wildlife habitat capacity = 52.47 ± 17.71. The ecozone+ is divided into the four regions described in Figure 36: Lake Erie Lowland (HC = 38.22 ± 14.06); Manitoulin-Lake Simcoe (HC = 52.26 ± 12.15); Frontenac Axis (HC = 64.87 ± 4.16); and St. Lawrence Lowlands (HC = 56.88 ± 17.06). Habitat Capacity was very low on the western tip of the ecozone+ and in the area around Montreal. Capacity in the rest of the ecozone+ was low to moderate, with small areas of high capacity on Manitoulin Island and east of Montreal. Small patches of very high capacity are found east of Toronto and west of Montreal.

The 2006 map shows that overall wildlife habitat capacity = 50.01 ± 14.58. Habitat Capacity in the four regions was as follows: Lake Erie Lowland (HC = 37.8 ± 10.32); Manitoulin-Lake Simcoe (HC = 47.34 ± 8.33); Frontenac Axis (HC = 50.71 ± .74); and St. Lawrence Lowlands (HC = 56.71 ± 15.54). Very low habitat capacity remained in the western tip of the ecozone+ and spread eastward towards London and the southern edge of the Niagara Peninsula, while the amount of very low capacity in the area around Montreal decreased. The area of high capacity disappeared from Manitoulin Island, but the areas of high capacity east of Montreal increased in size. A small strip of very high capacity is found along the north edge of the Niagara Peninsula, although there is no longer an area of very high capacity east of Toronto.

The 1986 map shows that overall wildlife habitat capacity = 52.47 ± 17.71. The ecozone+ is divided into the four regions described in Figure 36: Lake Erie Lowland (HC = 38.22 ± 14.06); Manitoulin-Lake Simcoe (HC = 52.26 ± 12.15); Frontenac Axis (HC = 64.87 ± 4.16); and St. Lawrence Lowlands (HC = 56.88 ± 17.06). Habitat Capacity was very low on the western tip of the ecozone+ and in the area around Montreal. Capacity in the rest of the ecozone+ was low to moderate, with small areas of high capacity on Manitoulin Island and east of Montreal. Small patches of very high capacity are found east of Toronto and west of Montreal.

The 2006 map shows that overall wildlife habitat capacity = 50.01 ± 14.58. Habitat Capacity in the four regions was as follows: Lake Erie Lowland (HC = 37.8 ± 10.32); Manitoulin-Lake Simcoe (HC = 47.34 ± 8.33); Frontenac Axis (HC = 50.71 ± .74); and St. Lawrence Lowlands (HC = 56.71 ± 15.54). Very low habitat capacity remained in the western tip of the ecozone+ and spread eastward towards London and the southern edge of the Niagara Peninsula, while the amount of very low capacity in the area around Montreal decreased. The area of high capacity disappeared from Manitoulin Island, but the areas of high capacity east of Montreal increased in size. A small strip of very high capacity is found along the north edge of the Niagara Peninsula, although there is no longer an area of very high capacity east of Toronto.

Source: Javorek and Grant, 2011340

The major variability in the status of habitat capacity among regions in the Mixedwood Plains in 2006 primarily resulted from the amount and type of cropland, along with the relative share of pasture and natural/ semi-natural land.  The Lake Erie Lowland reported the lowest habitat capacity as cropland comprised over 82% of agricultural land (Corn/ Soybean close to 50%) with only 13% “all of other land” and 2% unimproved pasture.  The Lake Erie Lowland is part of the Southwest Physiographic zone (see Ecosystem conservation and Intact landscapes and waterscapes ). The Southwest has only 8% cover of forest and 10% cover of wetlands.  This low level of natural cover limits the ability of species to use the cropland for a single habitat requirement and have sufficient alternative land cover outside of the agricultural land base to meet their other habitat requirements, further compromising habitat potential. The higher habitat capacity in the Frontenac Axis , Manitoulin-Lake Simcoe, and Saint Lawrence Lowlands regions, was due to comparatively lower share of cropland (52, 66, and 66%, respectively) and greater “all other land” (21, 18, and 26%, respectively). These regions also have higher proportions of natural cover outside of the agricultural land base than the Lake Erie Lowlands, with percentages of natural cover ranging from 35 to 57%.161 This may mean that species which use agricultural land as part of their habitat may be able to find nearby natural land cover to complete their habitat requirements.  The significantly higher “all other land”(woodland and wetland found on land defined as agricultural) component within the agricultural land base in the St. Lawrence Lowland was the main reason for this region reporting the highest habitat capacity on agricultural land in the Mixedwood Plains Ecozone+.  This is interesting in light of the fact that St. Lawrence Lowland’s associated physiographic area, the Eastern physiographic zone (see Ecosystem Conversion Key Finding) does not have the highest percentage of natural land cover in the ecozone+ (33% in the Quebec portion and 37% in the Ontario portion), that is found in the Frontenac Arch (57%),161 indicating that higher wildlife capacity on the agricultural land base may not necessarily be linked with higher wildlife capacity in the landscape as a whole.   There were other agricultural land use differences among these regions that impacted wildlife habitat capacity.  Intensive Corn/Soybean production was considerably higher in Saint Lawrence Lowlands (32%) and Manitoulin-Lake Simcoe (30%) compared to the Frontenac Axis which had less than 1% Soybean and 17% Corn.340 The Frontenac Axis, had considerably more Unimproved Pasture (20%); the second most important cover type for wildlife, than did the St. Lawrence Lowlands (5%) and Manitoulin-Lake Simcoe (9%).340 This difference may be partly explained by the fact that the Frontenac Arch is an extension of the Canadian Shield that has shallow soils over bedrock that do not lend themselves to farming generally, or cropland in particular, to the same extent as the flat clay plain of the St. Lawrence Lowland.161

The impact of fragmentation on bird species has been discussed in the literature mostly in relation to forest bird species; however, agricultural intensification can also impact bird species populations.  Jobin et al.(1996)342 studied the farmland bird populations in the St. Lawrence valley using 24 years of Breeding Bird Surveys starting in the 1960s.  They found that bird species diversity was higher in areas with diverse cover types than in those dominated by annual/ cash crops. Many species associated with dairy farming and perennial crop areas such as savannah sparrow (Passerculus sandwichensis), bobolink (Dolichonyx oryzivorus), brown-headed cowbird (Molothrus ater) and eastern meadowlark (Sturnella magna), showed decreasing population abundance between 1966 and 1990.342

When trends in the birds of open and grassland habitats were examined for the ecozone+ as a whole,343 it was found that both of these assemblages were experiencing declines.  The grassland birds show dramatic declines particularly since the 1980s.  Several species have lost 50% or more of their population over the last four decades, likely due to the combined effects of loss of marginal farmland to forest and more intensive use of remaining agricultural lands, where most of these birds nest and winter (Figure 35).343 Analysis of long-term data from several different bird surveys confirms significant declines in birds of grassland and open/agricultural habitats in the Mixedwood Plains.213 This trend is not unique to the Mixedwood Plains as grassland birds are declining throughout North America.344

Figure 35. Annual indices of population change of grassland birds in the Mixedwood Plains Ecozone+
line chart
Long description for Figure 35
This line graph shows the following information:
YearAbundance Index
1968167.3
1969164.7
1970150.7
1971154.8
1972158.3
1973145.1
1974150.0
1975155.4
1976166.0
1977166.6
1978157.1
1979149.6
1980135.0
1981150.2
1982142.6
1983134.0
1984120.7
1985113.5
1986112.9
1987100.1
198891.2
1989103.3
199095.6
199190.5
199281.8
199387.2
199488.6
199595.9
199684.9
199785.4
199877.1
199976.4
200074.2
200166.4
200258.8
200360.2
200456.4
200552.1
200651.3

Source: Downes et al., 2011343

The number of wind farms in Ontario has increased dramatically in the last few years and this trend is expected to continue. There are concerns that the presence of the wind turbines might result in lower nesting densities of bobolinks, eastern meadowlarks, and other grassland birds because of avoidance or abandonment of areas too close to the structures.345,346 An even greater threat may be the increase in intensive agricultural practices in some areas, accompanied by loss of hedgerows.343

When birds of open or agricultural habitats were examined343 (Figure 36) declines were seen to include raptors, passerines, and short-distance and neotropical migrants, suggesting that problems on the breeding ground may be a common factor.343 Declines were seen in the aerial insectivores found in this assemblage, a group which is also declining nationally.347,348 Loss of old-field habitat due to succession and the intensive use of remaining agricultural lands may be contributors.343

Figure 36. Annual indices of population change of open habitat birds in the Mixedwood Plains Ecozone+.
line chart
Long description for Figure 36
This line graph shows the following information:
AnnéeIndice d’abondance
1968111.1
1969123.6
1970156.1
1971134.6
1972113.6
197397.6
1974116.1
1975126.6
1976152.9
1977147.4
1978155.2
1979137.7
1980141.0
1981139.0
1982149.6
1983129.4
1984122.2
1985123.8
1986121.2
1987120.9
1988104.8
198997.4
199089.5
1991101.7
199283.6
199389.6
199479.2
199588.0
199697.3
199785.4
199887.8
1999102.5
200077.6
200177.6
200274.3
200375.0
200469.8
200574.5
200667.1

Source: Downes et al., 2011343

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Key finding 17
Species of special economic, cultural, or ecological interest

National key finding
Many species of amphibians, fish, birds, and large mammals are of special economic, cultural, or ecological interest to Canadians. Some of these are declining in number and distribution, some are stable, and others are healthy or recovering.

It is estimated that approximately 30,000 species live in the province of Ontario.146 While the status of many species is well known, occurrence data for the majority of species is incomplete and their conservation status consequently obscure. For example, there is little information on how may fungi349 occur in the ecozone+, and while the occurrence of some insect orders, such as Lepidoptera (butterflies) and Odonata (dragonflies and damselflies) is well-known, knowledge of most invertebrate groups is generally poor.  In 2005, the Canadian Endangered Species Conservation Council (CESCC) assessed the status of 4,217 Ontario’s species through “Wild Species 2005”.258  Though most of the assessed species groups comprise species with secure populations, the majority of both freshwater mussels and reptiles species fall into categories of conservation concern (Sensitive, May be at risk, At risk) (Figure 37).

Figure 37. The number of Ontario native species which are secure or of conservation concern based on the General Status Rank categories, 2005.
bar chart
Long description for Figure 37
This stacked bar graph shows the following information:
GroupeÉteinteDisparueEn périlPeut être en périlVulnérableSécurisée
Plantes vasculaires (n = 1957)-1,1%2,8%22,5%9,4%64,1%
Moules d’eau douce (n = 40)--20,0%25,0%22,5%32,5%
Cicindèles (n = 14)---14,3%7,1%78,6%
Libellules et demoiselles (n = 161)---26,7%24,2%49,1%
Papillons (n = 130)-1,5%-14,6%16,9%66,9%
Écrevisses (n = 7)----28,6%71,4%
Poissons d’eau douce (n = 127)0,8%3,9%7,9%2,4%16,5%68,5%
Amphibiens (n = 26)-7,7%19,2%3,8%0,0%69,2%
Reptiles (n = 25)--48,0%-20,0%32,0%
Oiseaux (n = 301)0,3%0,3%5,3%3,3%7,0%83,7%
Mammifères (n = 66)--4,5%3,0%13,6%78,8%
Tous les groupes d’espèces (n = 2854)0,1%1,1%3,8%18,6%11,0%65,4%

Source: Ontario Biodiversity Council, 2010213 based on original data from the Canadian Endangered Species Conservation Council 2006.

Based on COSEWIC (Committee on the Status of Endangered Wildlife in Canada) at-risk categories and species that are tracked by provincial conservation data centres, there are 865 species of conservation concern in the Mixedwood Plains (Table 12).  Approximately two thirds of the assessed species were vascular plants, and the taxon with the greatest number of species of conservation concern was vascular plants.

Table 12. Species of conservation concern in the Mixedwood Plains, 2009. Species tracked by the Ontario Natural Heritage Information Centre and Centre de données sur le patrimoine naturel du Quèbec are included as well as species identified as being at risk by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC). SC= Special Concern, THR=Threatened, END=Endangered, EXP=Extirpated. The COSEWIC-listed species are a subset of the tracked species. The data are valid as of February 12, 2009.
TaxonNumber of tracked speciesCOSEWIC - SCCOSEWIC - THRCOSEWIC - ENDCOSEWIC - EXP
Mammals12211-
Birds37746-
Reptiles2441051
Amphibians121331
Fish and Lampreys4513751
Insects740011
Other Invertebrates40008-
Vascular Plants5841119392
Non-vascular Plants37331-
Total8654147696

When the number of species within a species group is taken into consideration, reptiles are proportionally the group of greatest concern, followed by mussels, amphibians, and fishes.  Determining the most appropriate actions for conservation should be done based on more than just declining population trends,350 information such as abundance, breadth of range, rate of habitat loss, and whether the trend is part of a long term decline or if the species has a history of population fluctuation are all important factors.350 Declines in freshwater mussels, fishes, bumblebees, and reptiles and amphibians are presented in this key finding as examples of some of the changes in species populations occurring in the Mixedwood Plains.

Freshwater mussels

Southern Ontario has the highest diversity of freshwater mussels in Canada118 and all of the 41 species known to occur in Ontario are found in the Mixedwood Plains Ecozone+351 Most species of freshwater mussel have a specialized and unique life history strategy in that they require host fish for the dispersal of their larvae.252 This relationship means that the recovery of rare mussel species is highly dependent on the host fish species.353 When mussel populations for the Great Lakes basin were examined from 1860 to 1996 (136 years) it was found that the number of species had been decreasing and that community composition had shifted,132 with the abundance of silt and pollution-tolerant species (subfamily Anodontinae) having decreased.  Over the last two to three decades, four species of mussels have been lost from the Sydenham River, ten from the Thames River, nine from the Grand River, and there has been an almost complete collapse of the Great Lakes populations, likely due to the combined effects of intense agriculture, urban development, and the invading zebra mussel.354 Several refugia for mussels have been found in the Great Lakes at Metzger Marsh, Crane Creek Marsh, and Thompson Bay on Lake Erie in Ohio.355 The Lake St. Clair delta provides a refuge for the largest mussel community in the lower Great Lakes and this site includes several species within its populations that have been listed as endangered or threatened in Canada and/or the State of Michigan making it an important refuge for the conservation of native mussels.355 It is believed that the offshore currents in the delta mitigate the ability of zebra mussel veligers to infest the native mussel species (zebra mussels will cling to the surface of native mussel species using them as substrate to grow on thus decreasing the survivorship of the native species) in the nearshore compared to offshore waters, thus creating a refuge for the native mussels.355 The highest diversity of freshwater mussels in Quebec is observed in the Mixed Wood Plain Ecozone; the Saint-François River harbors 12 species of the 23 species found in Quebec.356

Birds

When the results of the Breeding Bird Survey were examined from the 1970s to the 2000s, it was found that trends differed by habitat group. Birds of woodland habitat have fared best overall, while grassland birds and other birds of open/agricultural habitat have declined as a group since the 1970s (Table 13). Grassland birds showed the greatest decline of all groups with the abundance within the ecozone+ having dropped by over 60% since the 1970s.343

Table 13. Trends in abundance of landbirds for the Mixedwood Plains Ecozone+.
Species AssemblagesTrend (%/yr)PBBS Abundance Index - 1970sBBS Abundance Index - 1980sBBS Abundance Index - 1990sBBS Abundance Index - 2000sBBS Abundance Index - Change(%)
Forest Birds1.1 50.656.964.267.333
Shrub/Successional0.1 117.2123.5122.5125.27
Grassland-3.1*155.4120.386.459.9-61
Other Open-1.8*133.8124.990.474.8-44
Urban/Suburban-0.7*425.
9
394.3364.4352.2-17

Source: Downes et al., 2011343

The general increase in birds of woodland habitats is likely a result of  increases in forest cover that have occurred in some portions of the ecozone+ (see Forests). However, not all forest dwelling species are doing well; for example the Eastern wood pewee has declined by 55% since the 1970s.343 This species undertakes long-distant migration to South America and is also of one of many species that feed on flying insects that are experiencing declining populations. Some of the other species showing decline, such as veery (-31%), are interior forest nesters which tend to decline in abundance in forest patches with less than 20 ha of interior forest.357 Decreases in grassland birds have been attributed to agricultural intensification, loss of hedgerows, vegetation succession, and the increased use of chemical pesticides (see also Ecosystem  conversion and Agricultural landscapes as habitat ).343 Research from the United States also raises concern over the increase in wind turbines in grassland habitats and possible avoidance of areas close to turbines by species such as bobolinks and eastern meadowlark.345 Decreases in birds of open/agricultural habitat are also attributed to habitat loss due to succession and intensification of use in remaining agricultural lands.

The decline in urban/suburban birds is less understood as these species are united by their tolerance of human presence. Declines in chimney swifts (-77%) are consistent with the declines in other aerial insectivores and with the loss of old-fashioned chimneys (due to capping and lining)343 but the declines in introduced species, such as house sparrow (-56%) and European starling (-35%), are harder to explain. In Europe, similar declines in house sparrow have been attributed to decreases in the numbers of chicks fledging due to decreases in the abundance of invertebrate prey.358 Other reasons for decline may be loss of nesting habitat and increases in pollution and predators.343  

Significant declines in breeding populations of shorebirds were found between 1968 and 2006 in four of five species covered by the Breeding Bird Survey, with declines as high as 80% for spotted sandpiper and -64% for American woodcock.359 Wetland birds are also experiencing declines.  Four of ten colonial waterbird species are declining in the Great Lakes. Great black backed gull is declining due to botulism and the common tern is probably declining due to competition with ring-billed gulls.360  Many marsh birds are also declining with the contributing factors including habitat loss and degradation, altered water levels, and invasive species.360

American black duck

Over 90% of the world population of American black ducks breed in eastern Canada361 and the population declined by almost 50% between 1955 and 1985.362 One of the most abundant ducks in eastern Canada, the population has been stable at about 450,000 since 1990, although declines continue in the Mixedwood Plains.363,364 Causes for the decline are not clear but likely include habitat loss due to development and agriculture362,365,366 and displacement through competition with mallards367 which have been expanding in abundance and range.362,365,366 Population increases in other areas could be due to changes in management practices, such as increased hunting restrictions.369

Freshwater fish

The Mixedwood Plains has the highest diversity of freshwater fishes in Canada.117 The fish of this ecozone+ represent 97% of the total fish taxa for Ontario and 86% of the total for Quebec.  Combined, the ecozone+ represents 78% of the total number of species for Canada.370 The majority of the rare fish species in the ecozone+ are fluvial specialists (flowing water obligates).371,372 Comprehensive data are not available to allow for discussion of overall trends, but individual studies are available which provide some insights into the kinds of changes that are taking place within fish communities within the ecozone+.  

Of the 21 species for which there is monitoring data for Lake Simcoe, seven species decreased in abundance between 1995 and 2003.373 Surveys of two tributaries of Lake Ontario in 2000 captured only 10 of 22 historical species in Carruthers Creek and only 28 of 50 historical species in Duffins Creek.122  In the Speed River (near Guelph Ontario), the ranges of cold-water species have contracted toward the headwaters while warm-water species have expanded their ranges upstream over the last 25 years.121  In the Grand River, brook trout populations have disappeared or have been severely reduced in some reaches.103 In a study of four shallow warm-water lakes in the Kawartha Lakes between 1980 and 2003,111 consistent declines were found for walleye (Sander vitreus vitreus) populations while increasing trends were seen for smallmouth bass (Micropterus dolomieu) and largemouth bass (Micropterus salmoides) populations.

One of the fish species most at risk in the Ontario section of the ecozone+ is the redside dace (Clinostomus elongatus), whose historic range included what is now the most heavily populated parts of southern Ontario. It is sensitive to alterations in flow regime, water temperature, and siltation, and its remaining populations are found in areas of rapid urban development.  Its status was uplisted from threatened to endangered by COSEWIC in 2007.374

The copper redhorse (Myxostoma hubbsi) is the fish species facing the highest risks of extinction in the St. Lawrence Lowlands. The Richelieu (downstream of Chambly Basin) and Mille-îles Rivers and reaches of the St. Lawrence River connecting the latter represent the extent of the range for this rare and endemic species to Quebec. The COSEWIC declared the species threatened in 1987 and upgraded its status to endangered in 2004. The present population is estimated to a few hundred individuals. The recovery plan put in place in 2004 aims, amongst others, to improve natural reproduction by protecting and restauring its critical habitat, enhance recruitment through fish stocking and protect the species habitat through regulatory measures. The facts that the species reaches sexual maturity at age 10, spawns in late fall, has a weak recruitment and has a very restricted diet are all compounding factors acting on the vulnerability of the species. Significant protecting measures are needed to curb nutrients and toxic pollution originating from agricultural, municipal, and industrial activities as well as habitat destruction in order to avoid witness the extinction of this endemic species to the St. Lawrence Lowlands.375

Bumblebees

Throughout Europe and North America, declines in bumblebees have been documented.376,377 In the vicinity of Guelph, Ontario, a comparison of bumblebee populations between the 1970s and 2004/06 revealed that 7 of the 14 species found in the 1970s were no longer present.377 One species, the rusty patched bumblebee (Bombus affinis) was found to have declined dramatically in abundance not only in southern Ontario but throughout its entire native range.377 The reasons for the decline are not well understood but possible explanations include habitat loss, pesticide use, introduction of disease from managed bees, and climate change. The rusty patched bumblebee was assessed as endangered by COSEWIC and listed as Endangered under Ontario’s Endangered Species Act, 2007. Declines in bumblebees in the American midwest have been found to coincide with large-scale agricultural intensification.376  When the attributes of bee species experiencing decline were compared using three independent faunas in Britain, Ontario, and Sichuan, it was found that species with narrow climatic ranges, which occur close to the edges of those ranges, or which have queens that become active later in the season were the most susceptible to decline.378

Reptiles and amphibians

There are 26 native species of reptiles and 25 native species of amphibians found in the Mixedwood Plains Ecozone+. They are the most imperilled of all the assessed species groups.  Of these 51 species, 26 (approximately 51%) were assessed as at risk by COSEWIC in 2008.11 Of the 12 species found in Canada only in the Mixedwood Plains, all (100%) are at riskFootnote ten x. Turtles appear to be in the greatest peril as seven of the eight native species (87.5%) found in the ecozone+ are at riskFootnote eleven xi. Snakes are similarly imperilled, with 11 of 17 (65%) of the species found in the ecozone+assessed as at risk.11

In both Ontario and Quebec, most amphibian monitoring is conducted by volunteer citizen based science programs. When data from the Marsh Monitoring Program for the Great Lakes basin (Canada and United States) were analyzed, statistically significant declining trends were detected for American toad, western chorus frog, green frog, and northern leopard frog   (Figure 38). None of the commonly found species had a positive trend. Mink frog (not as common) exhibited a significantly increasing trend between 1995 and 2007.147 Declines in chorus frog, green frog, and wood frog have also been reported by other authors.379,380 In Quebec, western chorus frog has declined dramatically. Since 1950, this species has disappeared from more than 90% of its range in the Montérégie region. The major reason for this decline is habitat loss to urbanisation and agriculture. The species is also declining in the Outaouais region.381

Figure 38. Figure 38. Amphibian trends in the Great Lakes Basin, 1995-2007. Graphs depict change in the annual occurrence index that shows the percent of monitoring stations where the species was recorded from the Marsh Monitoring Program
Images of amphibians
Long description for Figure 38
These eight line graphs show the following information: Annual occurrences indices
AnnéeCrapaud américainRainette faux-grillon de l’ouestGrenouille léopardOuaouaronRainette versicoloreRainette crucifèreGrenouille des boisGrenouille verte
199555,5673,3433,2552,4458,1568,3628,768,86
199655,861,0847,7147,0477,6876,4439,6568,3
199751,9360,3351,6445,9368,3482,1226,9471,98
199851,2858,5265,4253,6766,6388,7229,6186,39
199944,875640,9649,3764,8975,8330,1260,38
200044,4449,8243,6634,9170,5372,1523,7457,21
200146,7152,2135,0141,5866,7277,6430,7962,92
200250,4157,5531,744477,4190,333,6863,33
200351,8148,4945,9431,3471,4285,1125,3258,04
200437,251,6435,3247,5574,2189,6123,568,13
200546,0150,9439,532,3462,4684,7731,7166,33
200645,3242,9739,6442,9261,580,0626,3565,67
200740,3743,9637,0945,154,9470,2734,7766,28

Source: adapted from Archer et al. 2009147 Photos: dreamstime.com: American toad, Spring peeper, Wood frog, and Green frog; and iStock.com: Western chorus frog, Northern leopard frog, Bullfrog, and Gray treefrog

The COSEWIC status reports for Massasuaga rattlesnake (2008), blue racer (2002), eastern  hog-nosed snake (2001), and wood turtle (2002) demonstrate dramatic range reductions and local extirpations in the Mixedwood Plains Ecozone+.382,383,384,385

There are many reasons for the declines in reptile and amphibian populations. As with most species in the ecozone+, one major factor is habitat loss and fragmentation.386 Road mortality is an issue for both reptiles and amphibians.325,387,388 Daigle and Jutras (2005),389 found that a wood turtle population declined by 50% in seven years and attribute that decline to habitat modification, road mortality, and farm machinery mortality. Female turtles are particularly at risk as they are often hit by vehicles during their nesting migrations.390,391

Environmental pollutants are another cause of declines. Broad spectrum herbicides based on glyphosate have been found to kill between 68 and 86% of juvenile amphibians after one day.392 High levels of PCBs, organochlorine pesticides, and dioxins/furans have been reported in turtles in Ontario.393

Chytridiomycosis (Batrachochytrium dendrobatidis- a fungal disease impacting amphibians) has had widespread impacts on amphibians worldwide, including the Mixedwood Plains. It has been found in a number of common amphibian species in 30 locations in the St. Lawrence River Valley of Quebec.394 More research is needed to determine the best ways to mitigate the impacts of chytridiomycosis, and to understand how influences such as habitat alteration, projected climate change, and exposure to chemical pollutants interact to cause the observed population impacts.

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Key finding 18
Primary productivity

National key finding
Primary productivity has increased on more than 20% of the vegetated land area of Canada over the past 20 years, as well as in some freshwater systems. The magnitude and timing of primary productivity are changing throughout the marine system.

Evidence from Ontario

Net primary productivity (NPP) is a measure of the amount of plant biomass per area produced over time. Factors that influence plant growth therefore also govern the amount of primary production in any given area.395 Large-scale estimates of terrestrial NPP are usually made using remotely sensed data and tend not to take into account the production of below-ground biomass; they therefore likely underestimate actual primary production.396

NPP estimates from satellite data reported for Canada range from a high of 700 grams of carbon per square meter per year (g C m-2 year-1) in the southeast part of Vancouver Island to a low in the far north of less than 1 g C m-2 year-1.397 The mean NPP for the Mixedwood Plains is estimated at 257 g C m-2 year-1, although forested areas within the Niagara Escarpment and Frontenac Arch (which have 43 percent forest cover) have values as high as 500 g C m-2 year-1 and, therefore, some of the highest NPP in the country. The mean NPP for the ecozone+ is reduced by the low production of crop lands (average NPP values of 220 g C m-2 year-1) and urban and industrial areas. Hicke et al., (2002)398 examined trends in North American net primary productivity derived from satellite observations from between 1982 and 1998. Most of the Mixedwood Plains (aside from an area in Ontario around Guelph and Midhurst) showed a positive trend of increasing NPP of approximately 2 g C m-2 yr-1, with increases between 2 and 20%. The greatest increases were in the eastern Quebec portion of the ecozone+. These authors found that the maximum monthly trend in NPP was in August, September, or October for the Mixedwood Plains. Though this work is at a very coarse scale, it appears to demonstrate that those areas of the ecozone+ with cropland had maxima in August, while those with more forest cover had maxima in September or October. Hicke et al., (2002)398 also found that over the 16-year study period, across North America in general, croplands had the largest mean increase in NPP followed by deciduous broadleaf forests. These cover types are common in the Mixedwood Plains. They attributed the increases in summer NPP found in the Mixedwood Plains area to an increased in precipitation in this part of the continent during the study period.

Estimates of NPP from physical, on-ground sampling are few for the Mixedwood Plains. Moore et al., (2002)399, who studied Mer Bleue Bog near Ottawa, found that NPP varied at microsites within the bog.  Bog-hummock NPP, for example, was estimated at 290 g C m-2 year -1 while bog-hollow NPP was 330 g C m-2 year. The average for the bog was about 302 g C m-2 year –1, while a nearby fen had an NPP of 360 g C m-2 year -1 (all vegetation strata combined). These values seem high relative to the numbers reported for cropland by Liu et al., (2002),397 however bogs and fens have continuous vegetation cover and multiple strata of vegetation (mosses, herbs, shrubs and trees) and this may be responsible for the higher values for NPP from this bog/fen area compared to those reported for crop lands by Liu et al., (2002).397

Though there has been little published on NPP that applies to this ecozone+, the following observations are offered: 

  • Natural ecosystems (at least in this ecozone+) generally have higher NPP than human-altered systems such as agricultural and urban areas; and
  • Even ecosystems traditionally associated with slow growth, such as bogs and fens, have higher levels of NPP than human-altered systems.

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Key finding 19
Natural disturbance

National key finding
The dynamics of natural disturbance regimes, such as fire and native insect outbreaks, are changing and this is reshaping the landscape. The direction and degree of change vary.

Since much of the Mixedwood Plains have been settled for at least two centuries, it is necessary to rely on historical accounts of disturbances to understand their former role in this landscape. Historically, insect outbreaks, fire, high wind speeds, and ice storms were the four main natural disturbance types that regulate forest dynamics in the ecozone+.

Fire

Reconstruction of pre-European vegetation and disturbance patterns from sediment analysis shows evidence of First Nations use of fire in this ecozone+ for both the clearing of agricultural land and for wildlife management.400 The extent to which fire was used by these early peoples is difficult to determine, but it is certain that the area burned would have been more than occurred from natural lightning strikes,401 with areas as large as several square kilometres cleared around First Nation communities.12 Estimates for the pre-settlement fire cycle range from 900 years402,403 to 700 to 93,000 years.404 Post settlement, the cycle is estimated to be 5081 years.402,403 If the Mixedwood Plains were dependent solely on stand-replacing fires as its main disturbance, early successional communities would virtually disappear from the landscape because of the very long cycle of major natural fires. Frequent surface fires are believed to have been the common fire type in the Mixedwood Plains405 and small scale gap disturbances were the normal disturbance agents driving species composition.

In Ontario today, all fires within the Mixedwood Plains receive full suppression either by municipal fire departments or the OMNR, depending on land tenure. No data is available on the area burned for the Ontario portion of the ecozone+406 and the ecozone+ no longer has a natural fire regime.

In Quebec, all fires within the ecozone+ also receive full suppression by the “Société de protection contre les incendies de forêts” or municipal fire departments. Data is available on forest fires for the time period between the first forest survey conducted from 1969 to 1975 and the third survey period occurring from 1990 to 1995.23 Over this period, fire affected only 0.06% of the forest cover. Fire was the most important disturbance agent found between the first and the second (1981 to 1988) inventory periods as it represented 76% of the total area disturbed. Its importance decreased considerably during the period between the second and the third inventory when it represent only 14% of the total area disturbed.23

Fire is a disturbance agent that creates unique site conditions for regeneration that are not duplicated by other natural (e.g. wind) forces or anthropogenic disturbances, such as forest harvesting.407,408,409 With the removal of fire as a disturbance agent, the amount of natural vegetation undergoing succession towards late successional stages may be increased above natural levels within protected areas where harvesting is not permitted. On the rest of the landscape, harvesting tends to limit the development of old growth stands. Fire removal may affect forest composition since tree species such as white pine, jack pine, and oaks species require fire for some of their regeneration processes.410

Prairie and savannah communities are particularly vulnerable to fire removal as they succeed into other ecosystem types relatively quickly if they are not burned. These ecosystems are some of the very few communities in which prescribed burns are currently used as vegetation management tool in the Ontario portion of the ecozone+. Many prescribed burns occur on private land and without a reporting requirement; there is therefore no data available for them.406 Prescribed burns generally emulate surface fires since they are never allowed to occur under weather conditions which would result in stand-replacing fires. This is a positive influence for biodiversity in the Mixedwood Plains Ecozone+, since these surface fires were likely the dominant type of fire in the system’s natural state.405,411 Although data are not available to quantify fire trends in the Mixedwood Plains, it appears that there is increasing recognition of the important ecological role of fire in ecosystems, and potentially better acceptance of using prescribed burns as a vegetation management tool, particularly for prairie and savannah communities.406 The ecological role of fire in the regeneration and disturbance of pine412 and oak413,414 forest is well known.  The use of fire to maintain these species could support biodiversity objectives.412 

Insect outbreaks

When the amount of forest land within the Ontario portion of the ecozone+ damaged by insects and diseases was examined for the period between 2001 and 2005, it was found that 14.8% had been damaged.415  Almost all of that land, 98.2%, was impacted by single species infestations; only 1.8% was due to multiple species infestations.  Forest tent caterpillar (Malacosoma disstria) and spruce budworm (Christoneura fumiferana) were responsible for about half of the damage in the Ontario portion of the ecozone+ (6.9%) while all other species combined to make up the remaining 7.9% of the impacted area.415

In forests within Quebec’s portion of the ecozone+, the area moderately or severely affected by insect infestations represented only 0.05% of the forest cover from the first (1969 to 1975) to the third inventory program (1990 to 1995).23 While this disturbance type represented approximately 19% of the total disturbed area between the first and the second inventory program (1981 to 1988), it increased to  57% of the total disturbed area during the period from the second and the third inventory program.23 In the northeastern North America, balsam fir (Abies balsamea (L.) Mill.) defoliation caused by spruce budworm outbreaks is one of the major natural disturbances leading to tree mortality in balsam fir and spruce stands.416 Spruce budworm outbreaks occur with a recurrence cycle of approximately 30 years, and their effects on forest productivity cannot be compared with any other insect in eastern North America.416,417 At the provincial scale, the last outbreak in Quebec (1975 to 1985) defoliated, on average, 14 million hectares annually418 and destroyed annually 139 to 238 million m3 of softwood on public lands419 leading to very important economic losses.

It is very difficult to know whether the levels of insect infestation by native species are higher than those experienced historically as no information exists to allow for comparison.  The area infested by non-native invasive forest insects such as gypsy moth (Lymantria dispar), emerald ash borer (Agrilus plannipennis), Sirex woodwasps (Sirex noctillo) is in excess of natural disturbance levels as those species never occurred naturally within the ecozone+.161

Severe winds

Historically wind disturbance is considered to have been a larger disturbance in this ecozone+ than fire.32,33,404,420 A surveyor’s note reconstruction from northern Wisconsin404 found that heavy blow down was more prevalent than fire disturbance in pre-settlement forests (the vegetation in Wisconsin is part of the same international ecozone+) and that blow down patches were both smaller and more complex in shape than those associated with forest fire.  The wind cycle was found to range from 450 to 10,500 years,404 to 1210 years.420  Wind cycles varied across landscapes, with some areas having cycles several orders of magnitude longer than others depending on the substrate, forest species composition, climate, and storm patterns.404

Areas within the Mixedwood Plains are located in one of Canada’s few “Tornado Alleys”, were tornadoes occur at higher frequency than elsewhere in the country. A narrow corridor from extreme southwestern Ontario near Lake St. Clair, northeastward to Stratford, Shelburne, and Barrie, has been the location of many of Canada’s worst tornados.421,422,423 A portion of southeastern Quebec is similarly affected.

Many of the tree species found in the ecozone+ have rooting systems and morphologies that make them less susceptible to blow down.424 When wind throw was examined within the forested lands in the Ontario portion of the ecozone+, only 0.01% experienced wind throw between 2001 and 2005.161 A similar situation was observed in Quebec,23 where it was found that from the first (1969 to 175) to the third inventory program (1990 to 1996), the area affected by partial or total wind throw represented only 0.02% of the total forest area. The affected area increased over time with 0.025% of the forest affected between the second (1981 to 1988) inventory and the third, while only 0.003% was affected between the first and section inventories.23 The Intergovernmental Panel on Climate Change425 has suggested that climate warming in this area will result in increased heat in the lower atmosphere, and therefore higher wind storm frequencies in the future.

Ice storms

Ice storms are another common disturbance of the forests of the ecozone+ occurring at 20 to 100 year intervals.27 The 1998 ice storm damaged forests throughout eastern Ontario and southwester Quebec.  In southwestern Quebec the ice was 80 to 100mm thick and all but 3% of trees with a diameter of greater than 10 cm lost at least some of their crown branches and 35% lost at least half of their crown.26 In eastern Ontario, the ice storm covered 604,000 km2 426  and was associated with an increase in patch isolation or fragmentation.27 When the impacts of the ice storm on maple sugar production were studied in eastern Ontario, it was found that ice storm damage on sugar maple crowns had significant effects on sap sweetness and syrup production capacity for up to six years after the storm.  After six years, trees with moderate and severe crown damage had recovered sufficiently to maintain root starch levels similar to trees that sustained light damage.426 Tree growth was also reduced for three years after the storm on moderately to severely damaged trees.426

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Key finding 20
Food webs

National key finding
Fundamental changes in relationships among species have been observed in marine, freshwater, and terrestrial environments. The loss or reduction of important components of food webs has greatly altered some ecosystems.

Evidence from Ontario

Human activities in the Mixedwood Plains Ecozone+have led to a number of changes in the relationships among species. Through either the alteration of habitat availability and quality or harvest of species, humans have changed the relationships between predators and prey and thus the population dynamics of the species within the ecozone+. Habitat loss and fragmentation have huge impacts on predator-prey relationships427 but the nature of the change that occurs depends greatly on whether the predator is a specialist or generalist. Specialist predators rely on a narrow array of prey and when their prey’s habitat is lost, there are serious impacts on that predator. If the predator is a generalist, it is assumed they can prey upon many species and are often better adapted to changes in the environment. A generalist predator may even benefit from habitat loss if the replacement habitat provides the predator with greater resources.427,428 Though the number of mammal species found in the ecozone+ has actually increased since European settlement (due to introductions and range expansions), the biodiversity has decreased through the reduction of population size of many important species and the extirpation of others.429

Many of the large carnivores found originally throughout the Mixedwood Plains have been extirpated from some, or all of their previous range within the ecozone+. Wolverines (Gulo gulo) and cougars (Felis concolor) were extirpated from the ecozone+ shortly after European settlement due to habitat destruction and human persecution.429  Black bears (Ursus americanus –an omnivore),  eastern wolf (Canis lycaon), Canada lynx (Lynx canadensis) and bobcat (Lynx rufus) are still found in those areas in the ecozone+ with significant forest cover,429 but no longer occur in much of the southern part of the ecozone+. Species such as European hare (Lepus europaeus), Norway rat (Rattus norvegicus), and house mouse (Mus musculus) were introduced by European settlers and are now naturalized species. Other species which were historically present and are tolerant of humans have benefited from human activities and have increased in number. The woodchuck (Marmota monax), raccoon (Procyon lotor), striped skunk (Mephitis mephitis), and eastern gray squirrel (Sciurus carolinensis) have benefited from the presence of humans and have increased in population.429 The northeastern coyote (Canis latrans) migrated here from the lower Michigan peninsula near Detroit into southern Ontario where hybridization with eastern wolves occurred.430 The hybridization has resulted in a larger body size and more wolf-like cranial features, probably allowing them to better hunt deer which facilitated their spread.430 In the absence of larger predators, the coyote431 and red fox (Vulpes vulpes) have become primary predators in the ecozone+.

White-tailed deer (Odocoileus virginianus) are a species of edge habitats associated with environmental disturbances. With the fragmentation of landscape in the Mixedwood Plains creating habitat, an abundance of food associated with agriculture, milder winters, and the loss of large predators, deer have expanded their range in the ecozone+ and increased in density beyond historic levels.432 In southern Ontario, as elsewhere, research has shown that high white-tailed deer densities alter forest plant communities and thereby affect habitat for other species.  Under these conditions, the number of native plant species can be greatly reduced and spring flowers (ephemerals) are often reduced or absent.433 This relationship between spring flowers and deer grazing has led researchers to suggest that the height of the trilliums (Trillium grandiflorum) can be used to determine relative deer populations densities.434 Elk (Cervus elaphus canadensis), which were extirpated for the ecozone+historically, have been re-introduced to the province of Ontario and have expanded their range into the Mixedwod Plains ecozone+.434,435 In the Bancroft area where predation on elk is low, the reintroduced population has grown from 170 in 2001 to an estimated 500 in 2008.436

The population of double-crested cormorant (Phalacrocorax auritus –henceforth cormorant ) provides an interesting example of how a generalist predator’s population can be influenced by changes in its relationship with the environment and other species.437 Cormorants are a native species of the Mixedwood Plains, and though very high numbers for this species were reported in other parts of Canada prior to the 1800s, it is difficult to determine their pre-settlement population levels within the ecozone+ due to lack of records.438 By the late 1800s and early 1900s, it is believed their populations were in decline due to persistent human persecution as the species was seen as competition for fisheries resources.438 The population partially recovered through at least the mid-1900s, but experienced a major decline throughout  the 1950s to 1970s.438 By the late 1950s, a cormorant control program was initiated by the Ontario government due to concerns for recreational and commercial fisheries.437 Through the 1960s and early 1970s, cormorant populations experienced a dramatic decline due to reproductive failure.  This was caused by eggshell thinning to the point that the eggs could not support the weight of adult during incubation.437 The thinning was caused by high levels of organochlorines (primarily DDT) in the Great Lakes being passed on to the cormorants through their diets.439,440 New regulations, enhanced enforcement, and public awareness concerning toxic contaminants resulted in a ban on the use of DDT, significantly reducing levels of toxic chemicals and as a result cormorant reproductive success returned to relatively normal levels by the late 1970s.437  Recovery was also aided by enhanced over-winter survival of cormorants due to the consumption of catfish from the aquaculture industry in the southern United States.437,441 At the same time alewife and rainbow smelt which are primary food sources for cormorants in the Great Lakes experienced significant population increases due to the decline of large predatory fish.437,442

Throughout the 1990s, cormorant populations on the Great Lakes continued to increase437 at a rate of about 29% per year.443 From 2000 to 2005, populations began to show signs of stabilization (Figure 39). A comparison of cormorant diets before and after the introduction of the invasive round goby (Neogobius melanostomus) demonstrated that cormorants switched from eating yellow perch (Perca flavescens), alewife, threespine stickleback (Gasterosteus aculeatus) and smallmouth bass (Micropterus dolomieu) to eating dominantly round goby.443 Not only did the cormorants switch the species they were eating but they had to change their feeding method as the round gobies are located near the bottom of water bodies (benthic). The round gobies may be buffering predation of the native species previously consumed by cormorants.443

Figure 39. Great lakes-wide cormorant nest counts, 1979–2005. Dashed line indicates projected nest counts for years with missing or incomplete data.
line chart
Long description for Figure 39

This line graph shows the number of cormorant nests counted in each of the Great Lakes and Upper St. Lawrence River from 1979 to 2005. For Lake Ontario (Canada & U.S.), the number of nests counted increased steadily from 0 in 1981 to a high point of about 28,000 in 2002, with a slight drop off to about 25,000 by 2005. For Lake Huron (Canada only), counts began at 0 in 1979 and rose to about 17,000 in 1993, the last year for which complete data is available. Counts were then projected to rise to 29,000 by 2000 and then decline to 20,000 by 2005. For Lake Erie (Canada & U.S.), nest counts rose from 0 in 1984 to about 2,500 in 1990. They were projected to rise to 19,000 by 2005. For Lake Superior (Canada only), counts rose from 0 in 1991 to about 1,000 in 1998 and were projected to continue to rise to 3,000 by 2005. For the Upper St. Lawrence River (Canada & U.S.), counts rose from 0 in 1979 to about 2,500 in 1993 and were projected to rise to 3,000 by 2005.

Source: Weseloh et al., 1995, 2002, and 2006, Canadian Wildlife Service, unpublished data, OMNR, unpublished data. Shieldcastle, unpublished data, as reported in, OMNR 2006437

Footnotes

Footnote x ten

All species designated by COSEWIC were considered including those currently extirpated.

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Footnote xi eleven

The box turtle was not considered as it has not been determined whether it is a native species.

Return to footnote eleven xi