The social, economic and cultural health of Ontario is influenced by climate. Vulnerability to climate variability and change is demonstrated by the impacts of recent severe weather events, such as drought, intense rainfall, ice and windstorms, and heat waves. Those impacts include water shortages, lower Great Lakes water levels, flooding, forest fires, reduced agricultural production, damages to infrastructure and property, power outages and outbreaks of water-borne diseases.
Since 1948, average annual temperatures in Ontario have increased by as much as 1.4 °C. This trend is projected to continue, with the most pronounced temperature increases occurring in winter. Projections also indicate that intense rainfall events, heat waves and smog episodes are likely to become more frequent.
Physical infrastructure, water quality and supply, human health and well-being, remote and resource-based communities, and ecosystems are highly sensitive to climate. The degree to which the associated systems are vulnerable depends on their ability to successfully adapt to changes in both climatic and non-climatic stresses.
Disruptions to critical infrastructure, including water treatment and distribution systems, energy generation and transmission, and transportation have occurred in all parts of the province, and are likely to become increasingly frequent in the future. In recent years, flooding associated with severe weather has disrupted transportation and communication lines, with damage costs exceeding $500 million. Lengthy and extensive power outages have resulted from the failure of transmission grids and distribution lines. Projected decreases in Great Lakes water levels may compromise shipping and reduce hydroelectricity output by more than 1100 megawatts.
Water shortages have been documented in southern regions of the province, and are projected to become more frequent as summer temperatures and evaporation rates increase. Sections of Durham County, Waterloo and Wellington Counties, and the shoreline of southern Georgian Bay, where growth strategies indicate that the population will continue to increase significantly, will become more vulnerable to shortages within the next 20 years.
The health of Ontario residents has been at risk of illness, injury and premature death from such climate-related events as extreme weather, heat waves, smog episodes and ecological changes that support the spread of vector-borne diseases. Heat-related mortality could more than double in southern and central Ontario by the 2050s, while air pollution mortality could increase about 15 to 25% during the same interval. Extreme heavy precipitation events, such as the one in May 2000 that contributed to the E. coli outbreak in Walkerton, Ontario, which killed 7 people and made 2300 ill, are projected to increase. Adaptation, in the form of smog alert advisory systems, is now commonplace, and some cities have recently introduced heat-health alert systems.
Remote and resource-based communities have been severely affected by drought, ice-jam flooding, forest fires and warmer winter temperatures, which have caused repeated evacuations, disrupted vital transportation links and stressed forestry-based economies. Projected increases in winter temperatures will further reduce the viable operating season of winter roads, limiting access for the delivery of construction materials, food and fuel to many communities and mine sites in the far north. Increased frequency of forest fires and outbreaks of forest pests will adversely impact the health and economic base of communities dependent on the forest industry, particularly in the far northern parts of Ontario's boreal forest.
Ontario's ecosystems are currently stressed by the combined influence of changing climate, human activities and such natural disturbances as fire and outbreaks of insects and disease. Wetlands are particularly sensitive and have undergone dramatic declines in recent years, especially in southern Ontario. Observed changes in the relative abundance of fish species in southern Ontario show a shift from cold- and cool-water species to more warm-water species. Changes in the composition of aquatic and terrestrial ecosystems in the Hudson Bay region, and reduced numbers and health of polar bears and seals, are other examples of current impacts. Lower water levels in the Great Lakes, as projected for the future, will further compromise the wetlands that presently maintain shoreline integrity, reduce erosion, filter contaminants, absorb excess storm water, and provide important habitat for fish and wildlife. Invasive species in the Great Lakes are likely to increase, requiring modification to infrastructure and/or management activities.
Ontario has a strong capacity to adapt to climate change, based on a variety of indicators, such as economic wealth, technology, information and skills, infrastructure, institutions, social capital and equity. However, this capacity is not uniform across subregions and sectors. Adaptation is starting to occur in Ontario. For example, climate change has been incorporated into some long-term planning and decision-making, most notably by some conservation authorities (e.g. for storm-water management) and public health departments (e.g. with heat-health alert systems). Opportunities exist for mainstreaming adaptation to climate change into decision-making through, for example, the Clean Water Act, and other legislation, regulations or planned activities that relate to, among other things, infrastructure renewal programs, low-water response programs and growth strategies.