Key Findings at a Glance
Habitat, Wildlife, and Ecosystem Processes
The key findings in this section are related to aspects of abundance and diversity of wildlife. First the capacity of agricultural lands to support wildlife is considered. Trends are then assessed for selected species groups of high economic, cultural, or ecological significance. Three aspects of ecosystem processes are then examined – primary productivity, relations of predators and prey through food webs and population cycles, and the role of natural disturbance in forested ecosystems.
Agricultural landscapes cover 7% of Canada’s land area and provide important habitat for over 550 species of terrestrial vertebrates, including about half of the species assessed as at risk nationally. Natural areas, including wetlands, woodlands, and unimproved pasture, provide the highest biodiversity values, while croplands provide the lowest. Between 1986 and 2006 the capacity of agricultural landscapes to provide habitat for wildlife declined significantly across Canada. The main causes are the conversion of natural areas to cropland and more intensive use of agricultural land. The proportion of agricultural land classified as cropland increased from 46 to 53% over this period.
Amphibians: Twenty percent of native amphibians – frogs, toads and salamanders – are considered at risk of extinction in Canada. Declines of several amphibian populations since the mid–1990s have been documented in the Great Lakes Basin and the St. Lawrence River corridor. Trends for western Canada are not well documented. Habitat degradation and loss are the main causes of amphibian declines in Canada.
Fish using freshwater habitat: Freshwater species are at a high risk of extinction worldwide. In Canada 18% of freshwater and diadromous fish are Endangered or Threatened in all of parts of their ranges. The number of Endangered or Threatened fishes has been increasing since the 1980s. The causes of declines vary across the country and include invasive non–native species, habitat loss, degradation, and fragmentation, overharvesting, pollution, and climate change.
Birds: Since the 1970s, overall population declines have affected all landbird groups except forest birds. Birds of grassland and other open habitats exhibited the most marked declines, losing over 40% of their populations. Some common landbird species are also showing declines. Half of the 35 shorebird species assessed in 2000 showed a decline somewhere in their ranges. Trends for seabirds are mixed, but the number of populations in decline has increased since the 1980s. Waterfowl are generally healthy, although some species are in decline.
Caribou: The range of caribou has contracted. Most northern herds are declining, some precipitously. Causes are not well understood and might include natural population cycles, climate change, increased impacts from human activity, changes in predation, and over–harvesting. Forest–dwelling woodland caribou are Threatened in the boreal forest, with many herds declining. The status of most herds in the northern mountain population is not well understood, while most herds in the southern mountain population are in decline. Woodland caribou are declining primarily because of loss and fragmentation of habitat.
The North, where temperature rise is highest, has experienced the largest increases in production of green vegetation. Productivity increases in southern Canada are likely related more to changes in land use than to changes in climate. Vegetation changes that correspond with northern Canada’s greening trend include a shift to shrubs and grasses where lichens and mosses once dominated. In Arctic lakes and ponds, a longer growing season for algae, due to earlier melting of lake ice in spring, is considered the strongest factor driving the observed increase in productivity. Marine primary productivity, however, shows long–term declines in most of the world’s ocean regions, including the Arctic, North Pacific and North Atlantic oceans.
Natural disturbance regimes, such as fire and native insect outbreaks, are important drivers of biodiversity in forest and grassland ecosystems. Large fires, greater than 2 km2, account for over 95% of the area burned, and over 90% of them occur in the boreal forest. Although highly variable, the annual area burned has increased since the 1960s. At the same time, fire is no longer a significant disturbance agent in parts of the country such as southern Ontario and the Prairies. No overall trend in native insect outbreaks is evident, although some insects, such as the mountain pine beetle, show significant change. The infestation of mountain pine beetle over the last decade was of unprecedented intensity, damaging over 163,000 km2 of forest. Fire and insects affect each other and both are influenced by climate and management practices.
An example of the impact from a major reduction in one food web component is the decline of Diporeia, a small relative of shrimp and historically the dominant invertebrate in most of the Great Lakes. This decline has had major consequences for Great Lakes fish populations and commercial fisheries. Reduction in predators also affects the whole food web. Most large native carnivore populations have declined severely in southern and eastern Canada, affecting abundance and diversity of prey species and small predators. Population cycles are important features of boreal forest and tundra ecosystems. Herbivores – especially the snowshoe hare in forests and small rodents in tundra – are at the heart of these cycles. There is emerging evidence that these population cycles are weakening at several locations in northern Canada.
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