1.Human Health
There is a serious threat to human health. In high latitude (Canada) and developed countries there is a danger of increased exposure to heat stress in very hot weather events, and more frequent weather hazards (e.g. droughts, floods, wildfires and severe storms) with resulting injuries, deaths and damage to infrastructure that supports public health.
From a global perspective the most alarming threat is an increase in transmission of vector-borne infectious diseases as the vector organisms spread and extend their range. Major increases are possible in the incidence of malaria, dengue and yellow-fever, schistosomiasis and river-blindness, events which are likely to compound conditions of poor environmental health conditions in many countries.
2.Water Systems
The quality and quantity of fresh water for domestic water supply, agriculture, hydroelectricity, thermal power generation, municipal and industrial water supply, water pollution abatement and inland navigation is already insufficient in many regions of the world, especially the arid and semi- arid areas. Even in North America, periodic water shortages in the U.S.A. have resulted in calls for increased diversions southward, from the Great Lakes. With climate change these stresses will extend to other areas, resulting in hardship, threats to health and, most serious to contemplate, strong competition for control of sources among competing users both within and between countries. Such competition is often a contributing cause of armed conflict.
3.Natural Ecological Systems
Natural ecological systems are now under heavy stress from human resource demands. Wildlife and fish stocks are endangered, with serious economic and socio-cultural consequences. Climate change will add a major additional stress factor.
The boundaries of ecosystem regions are likely to move a lot faster than most species can migrate, resulting in significant species loss and decline in biodiversity. Such dangers will have a direct impact on Canada. The most outstanding concern is for the future of the great boreal forest which could be reduced to a mere remnant of the present size.
4.Forests
Between 14 and 65% of the world's forested areas would undergo major changes in vegetation type, with implications for management and commodities. Large forested areas which now provide a large and varied supply of forest products are under threat from climate change because, like natural ecosystems, they cannot move (or be moved) rapidly enough to adapt to the poleward shift of temperate bands. A poleward shift in the range of 160-640 km. over the next 100 years is expected, while the historical migration rates for many species are in the range of 4-200 km per century.
Boreal forests (including Canada's) are particularly vulnerable: in addition to direct effects on growth, indirect effects such as increased forest fire frequency and pest outbreaks are likely to decrease average forest age, biomass and carbon storage.
5.Coastal ecosystems and coastal zones
Sea-level rise will have a number of negative impacts on tourism, ports, harbours, human settlements, agriculture, the insurance industry and cultural systems and values. There is serious risk of permanent loss of land - some of which is densely-populated in countries where available land for alternate development is in short-supply or non-existent. High-cost options to protect coastal areas from sea level rise do exist, but they are likely to be prohibitively expensive for all except the most committed governments. The largest impacts on Canada are likely to be experienced in the lower Fraser delta lands in B.C. and in a few coastal cities in eastern Canada including Charlottetown, P.E.I.
6.Agriculture
In aggregate, it seems that the gains and losses will average out, such that there will not be a major threat to world food production, assuming suitable and cost-effective adaptation measures can be implemented. On the other hand, the lesser ability to adapt agriculture to changed climate in some regions, especially the poorer regions of the planet, will have a potentially large regional impact, including security of food. There may be significant new opportunities for Canadian agriculture in a warmer world, provided sufficient precipitation occurs in food-producing areas. Other regions are likely to be adversely affected. In Canada, northward expansion of cultivation could also lead to conflict with existing land use and the stakeholders in forestry, wildlife habitat and hunting. This could pose an additional threat to native lifestyles.