Impacts: physical / biological

The impacts of a changing climate are already evident in every region of Canada. Unequivocal are the impacts of climate change on many physical and biological systems, such as ice and snow cover, river, lake and sea levels, and plant and animal distributions. In addition, increases in the occurrence of heat waves, forest fires, storm-surge flooding, coastal erosion and other climate-related hazards are consistent with observed climate trends.

Some observed impacts of changing climate on physical and biological systems in Canada

	Glacier cover – mass and area; widespread reductions with local variability	widespread retreat since late 1800s in western Canada, since 1920s in Arctic glaciers in BC are currently retreating at rates unprecedented in the last 8000 years estimated loss of ice mass in Canadian Arctic of 25 km3/a for period 1995–2000
	Snow cover – reduced annual extent and duration	10% decrease in extent in Northern Hemisphere for period 1972–2003 decrease of 20 days in duration of snow cover in Arctic since 1950
	Sea-, lake- and river-ice cover – reduced extent and duration	3% per decade decrease in annual average area of sea ice in Northern Hemisphere for period 1978–2003 reduction of ice cover season on Great Lakes by 1–2 months during past 150 years
	Permafrost conditions – warming and deepening of annual thaw layer	most significant warming in western Arctic 1°C increase in surface permafrost temperature since 1990 in northern Quebec increase in summer thaw penetration in the 1990s
	River and lake levels – changes in water levels and timing of peak flow events	decline in summer and fall runoff in Prairies, leading to lower lake and river levels at those times trend towards earlier spring runoff
	Plant phenology – events occurring earlier	26-day shift to earlier onset of spring over the past century in Alberta 5–6 day advance since approximately 1959 in the onset of phenological spring in eastern North America
	Plant productivity – lengthening growing seasons and increased productivity	greater productivity rates of spruce and poplar in Quebec lengthening of growing season for crop production
	Distribution of some animal species – northward or upslope shifts in terrestrial ecosystems, shifts towards warmer thermal regimes in freshwater ecosystems	increasing abundances of cool and warm water fish species relative to cold water species
	Coastal erosion – enhanced as a result of decreased ice cover, sea-level rise, increased storminess, and non-climatic factors	accelerated erosion and degradation of the dunes and coastline throughout the southern Gulf of St. Lawrence, northeastern Prince Edward Island and southwestern, western and eastern Newfoundland

Many of these impacts directly influence human systems. For example, decreases in the thickness and duration of lake and river ice have significantly impacted the viability of many winter road networks that provide access to remote communities and mine sites in northern Canada, while coastal erosion has impacted buildings and critical infrastructure, and threatened cultural sites on all of Canada's marine coasts. There is also strong evidence that climate change has been a contributing factor to a number of other environmental, social and economic issues.