Key finding overview
KEY FINDING 14. Rising temperatures across Canada, along with changes in other climatic variables over the past 50 years, have had both direct and indirect impacts on biodiversity in terrestrial, freshwater, and marine systems.
This key finding is divided into four sections:
- Key finding overview (this page)
- Climate trends for Canada
- Earlier springs lead to changes in timing of bird migration and nesting
- Warmer temperatures lead to changes in the tundra biome
Climate change includes a rise in global temperatures and more frequent extreme weather events, due to human activities that alter the chemical composition of the atmosphere through the buildup of greenhouse gases that trap heat and radiate it back to the earth’s surface.1 Climate change is important because climate shapes the distribution of organisms and the nature and character of ecosystems.2 Projected increases in temperature may exceed biological tolerances for many species and ecosystems in Canada, resulting in decreased capacity to recover from disturbances and increased risk of extinction for many species.3
Climate change affects all aspects of ecosystems and is at least part of the story in many of this report’s key findings.
Research provides us with understanding of how climate change affects ecosystems. Global climate models provide us with projections for future climates. Evidence of trends and abrupt changes, early warnings of deviations from established patterns, and local observations of ecological change, show us that impacts are happening now.
Climate trends for Canada, 1950 to 20075
- Average annual air temperature increased by 1.4ºC.
- Strongest warming (>2ºC) was in the west and northwest.
- No significant cooling trend occurred at any location in any season.
- Largest temperature increases were in winter (>4ºC at 26 locations).
- Warming was most prevalent in winter and spring, leading to widespread:
- decrease in winter snowpack and earlier snowmelt;
- earlier start to the growing season.
- Summer warming trends were mainly over southwestern and southeastern Canada.
- Smallest temperature change occurred in the fall.
- Annual precipitation generally increased, most strongly in the northern half of Canada.
- Precipitation increased over the Arctic in all seasons except summer.
- Winter precipitation decreased in southwestern and southeastern Canada.
- The fraction of precipitation falling as snow decreased in southern Canada.
Earlier springs lead to changes in timing of bird migration and nesting
The trend to earlier, warmer springs appears to be leading to earlier arrival at prairie nesting grounds for some waterfowl and earlier hatching for some seabirds.
Canada geese arrival dates, Delta Marsh
Timing of annual arrival at Delta Marsh, along the shore of Lake Manitoba, was strongly related to the average March temperature for about half of the 96 migratory bird species studied, including Canada geese. Spring arrival dates of most of these species shifted earlier at rates of 0.6 to 2.6 days for each 1°C rise in average March temperature.6
Hatching dates for tufted puffins, Triangle Island
Tufted puffins, rhinoceros auklets, and Cassin’s auklets at Triangle Island off the B.C. coast have shifted to an earlier breeding season in the past 30 years. The populations of these burrow-nesting seabirds declined from 1984 to 2004, likely due to changes in ocean conditions. The declines may be partly caused by a mismatch between timing of nest hatching and peak food availability, as has been confirmed for Cassin’s auklets.8
There are many observations throughout the country of shifts in species ranges, generally northward. Many of these shifts are likely related to climate change. Some examples include:
- The northern limit of the breeding range of landbirds that breed in southern Canada moved northward by an average of 2.4 km per year from 1964 to 2002 – for example, Swainson’s thrush has extended its range 141 km northward over this period.9
- Declining sea ice in Arctic straits has led to killer whales expanding their range into Hudson Bay where they are now sighted every summer.10
- Northward range shifts have been noted since the 1960s in the Northwest Territories for whitetailed deer, coyote, wood bison, cougar, magpies, and the winter tick parasite.11, 12
- White-tailed deer have been expanding northward from B.C. to Yukon since 1974 and now range as far north as central Yukon.13 They have also been observed to be expanding northward in Saskatchewan, Quebec, and Ontario.14, 15
- The Inuvialuit of Banks Island in the Arctic have noted new species of beetles and sand flies. Robins and barn swallows are also new to the region.16
- Northward expansion of racoons into the Prairies during the 20th century may be linked to longer growing seasons along with increased agricultural production.17
International Tundra Experiment (ITEX) site, showing open-topped greenhouses, Alexandra Fiord, Ellesmere Island, Nunavut
Warmer temperatures lead to changes in the tundra biome
Evidence from around the circumpolar Arctic indicates that tundra is changing.18, 19 Climate records show that the particular conditions of cold temperatures and low precipitation needed to support polar tundra, barrens, and ice and snow biomes declined about 20% in the past 25 years.20 This trend is linked with increases in primary productivity and increased biomass in tundra plant communities. This “greening” signal is particularly strong in the Canadian Western Arctic where there is evidence of shrub cover increasing in the forest-tundra and adjacent tundra. Studies based on satellite images from 1986 to 2005 along the treeline zone west of Hudson Bay show trends to increased shrubbiness, especially west of the Mackenzie Delta.21 In the delta, the combination of warming temperatures and increasing permafrost degradation is creating new growing conditions suitable for colonization by tall deciduous shrubs such as alder.21
Several sites in Canada conduct research and monitoring on changes in tundra through the International Tundra Experiment (ITEX). Analysis of vegetation plots from ITEX sites around the circumpolar Arctic shows that, although changes vary from region to region, increases in vegetation canopy height and dominance of shrubs are common findings.22 The ITEX program also includes passive warming experiments using small, open-topped greenhouses (see photograph) which increase plant-level air temperature by 1 to 3°C. Analysis of 11 ITEX warming experiments from around the Arctic indicates that future trends in tundra are likely to include increases in canopy height, changes in species composition and abundance, and reduction in species diversity.23
Increases in evergreen shrubs and mosses, Ellesmere Island, Nunavut
High Arctic tundra at the ITEX site on Ellesmere Island has become more productive, with biomass increasing by 50% over 13 years. This change was mainly due to an increase in growth of evergreen shrubs and moss. Because of the greater shrub growth, average canopy height increased, doubling from 17 to 34 cm between 2000 and 2007. Species diversity did not change.22
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