How might these changes affect Canada?

Impacts of climate change are expected to be greater in some regions than in others; these have been looked at in greater detail. At the same time, it must be noted that there is greater uncertainty for scenarios at the regional scale than at the global one. Researchers, through the use of GCMs and other methods, develop "scenarios" of possible future climates of a region. These scenarios are then applied to the ecosystem or economic regions to determine how that region would be affected by climate change.

One such investigation is based upon an ecological framework that expresses regional climate through the development of vegetation and soils. 

The underlying premise is that if all factors are held constant in sites that are affected by extremes, the vegetation and soil development over time will reflect the influence of climate. Using the data generated by a general circulation model for doubled atmospheric CO₂ concentrations, (i.e., a possible future climate), a scenario was generated illustrating how the location and quantity of existing ecosystems might change with time. 

As Canada is a large land mass in the northern mid to high latitudes, its interior is expected to experience a larger than average increase in temperature and a decrease in summer soil moisture. The north would have a greater increase in winter temperatures and more precipitation than now, particularly in winter.

Pacific coast

A rise in sea level would threaten low-lying coastal lands, such as the Fraser River delta, with possible increases in flooding and erosion. The increased precipitation considered likely in winter could promote landslides and local flooding.

Warmer river temperatures could cause severe pre-spawning mortality in some fish that go up rivers to spawn (anadromous), such as the Pacific salmon. However, warmer ocean temperatures could create favourable conditions for species such as tuna, hake, and squid to migrate from the south.

West Coast forest ecosystems could become more stressed as a warmer climate allowed insect pests and disease to migrate northward. Forests in the drier areas would become more vulnerable to fire.

Prairie provinces

The Prairies, the breadbasket of Canada, already suffer from periodic drought, especially in the south. With higher temperatures and increased evapotranspiration, drought would probably become more frequent. An increase in irrigation, if water was available, could bring more soluble salts to the surface, degrading the soil.

With a warmer climate, agriculture could move northward, into more humid (although still dry) areas. The poor northern soils would be more likely to limit its northern expansion than climate. Conflict between agricultural, industrial, or aboriginal interests could arise as a result of the spread of farming into new territory.

The forests could also expand to the north, although more slowly, as trees take much longer to mature than field crops. Some of the areas presently under forest may not be able to support trees, if the soil moisture, already low, is reduced much more. Low soil moisture stresses trees, making them more susceptible to pests, disease, and fire. It has been suggested that 170 million hectares of forest could be lost in the south and only 70 million hectares gained in the north, as they would be limited by poor soil or rock.

Great Lakes - St. Lawrence basin

Over 42.5 million people live in the Great Lakes - St. Lawrence basin. Over 29 million of them (including 8 million Canadians) depend on the lakes for drinking water. The quality of the water is already under stress as the region is a major centre of North American manufacturing.

According to researchers, the average temperature in the Great Lakes basin could go up by about 4.5°C by 2055, with slightly larger increases in winter than in summer. Higher rates of evaporation and drier soils would reduce runoff, and water levels in the Great Lakes could fall by an average of between 0.5 m and 1.0 m, according to typical scenarios. The St. Lawrence River outflow could be reduced by 20 percent.

Water is used intensively by industries such as primary metals, chemicals, food processing, and timber products. Water is also important, particularly to the grain and metal producers, for shipping. However, the biggest single user of Great Lakes water is the electric power industry. All of these industries would be affected by a significant change in the quantity and quality of the water supply.

While lower water levels would decrease the flow available for the generation of hydroelectric power, a warmer winter would also slightly lower the demand for electric power for heating. This might be counter-balanced by an increase in summer demand for power to run electric fans and air conditioners. Lower water levels would reduce the amount of cargo that ships could carry per trip, but a shorter ice season (by 5 to 12 weeks) might provide for a longer shipping season, allowing more trips per year.

Agriculture is the largest industry in the region, and forestry is a major one in the northern parts of the basin. Although the growing season would be longer, the reduction in soil moisture would be likely to decrease crop yields over time unless adaptive measures are taken. Higher temperatures and drier soils could also reduce the extent and health of forests of the basin, and the drying out of marshes would cut back on wildlife habitat. Some of the present fish species could disappear from the lakes due to warmer temperatures, while other species could migrate northward from southern parts of the region.

An unreliable "cold" season and a projected decrease in snowfall of from 20 to 80 percent, with the biggest change to the north of the lower Lakes, would substantially reduce the ski season for southern Quebec and virtually eliminate it in southern Ontario.

Water quality might also be affected in the following ways:

• the dredging needed to offset lower water levels could re-suspend toxic chemicals;
• higher water temperatures could decrease dissolved oxygen levels and increase the growth of algae and bacteria;
• less runoff and stream discharge would reduce the flushing out of bays and dilution of organic matter and chemicals;
• lower water levels could cause the disappearance of wetlands, which are valuable habitats;
• agricultural and urban expansion would continue to contaminate runoff with fertilizers and toxic chemicals.

The impacts of climate change on water quantity and quality might also increase external pressures on the Great Lakes water supply. For instance, lower water levels in the Mississippi River system might create an increased demand for diversion of Lake Michigan water. Infiltration of salt water into the New York City water supply due to rising sea levels might result in a request for a diversion of Lake Ontario water.

Atlantic Coast

A rise in sea level would threaten residential, transportation, and industrial facilities with flooding in low-lying communities along the coast, such as Charlottetown. The threat to a given area would be lesser or greater depending on whether the land itself was rising or subsiding. For instance, the Gaspé Peninsula is rising, while that of Newfoundland is subsiding.

The rise in sea level would increase the incidence of flooding, especially during storms. The serious storm surge and river flooding that may now affect Saint John, for instance, once in 100 years might in future occur once in 20 years.

Salt water intrusion could contaminate groundwater aquifers (the main source of regional water supplies), disturb sensitive estuary ecosystems, and displace freshwater fish populations. On the other hand, freshwater fisheries and aquaculture could benefit from the longer season resulting from a higher average annual temperature.

A rise in ocean temperature could affect the distribution and makeup of the fish population, limiting some species, encouraging others.

While higher temperatures would reduce the extent of sea ice, some scientists think that greater snow accumulation on Arctic ice caps and longer, warmer seasons at their edges might increase the calving of icebergs. It is not clear what effects the warmer temperatures would have on ocean circulation, wave patterns, and the frequency of tropical storms.

The North

A rise in sea level would also flood low-lying areas in northern Canada, such as the Mackenzie River delta, erode shorelines, and change near-shore ecosystems. However, higher temperatures would lessen the extent and duration of sea ice and facilitate shipping in the far north.

Inland, milder winters and longer summers would shorten the season for ice roads in many areas, reducing access to remote communities and to stands of timber. Gradual melting of the southern permafrost would change water drainage patterns and destabilize the land, affecting roads, pipelines, and buildings. The season for barge transport on the rivers would lengthen.

A longer growing season would allow agriculture to expand northward from its present limits, where soils and moisture permitted. The boreal forest would become more productive in the south, although its northward expansion would be limited by poor soils and slowly thawing permafrost. Fire could become more of a threat, as well.

An expected increase in precipitation, particularly in fall and winter, would result in a greater accumulation of snow, although over a shorter season, and the possibility of extensive and earlier flooding in spring. The higher precipitation could increase the net water supply in northern watersheds, expanding the potential for hydroelectric power. For instance, that potential in northern Quebec could increase by 15 percent.

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