Canada's Arctic has already experienced significant changes to its climate that are producing cascading effects on physical, biological, economic and social systems. The sensitivity of these systems to climate change is relatively high because of their dependence on the predictability and characteristic stability of the cryosphere (snow, glaciers, freshwater/sea ice and permafrost). Current climate trends are likely to continue and intensify, creating unique conditions, challenges and/or opportunities for natural and human adaptation.

Major changes are expected in a variety of resource sectors, including hydroelectric generation, oil and gas, mining, forestry and fisheries. Locally, hydroelectric facilities and operations will need to be adapted to changing flow regimes associated with an altered timing and magnitude of snowmelt runoff. Perhaps more important, however, will be a need to consider the implications of future impoundments as the needs for additional and renewable energy increase, particularly on the northward-flowing Mackenzie River system. Where older infrastructure in the Arctic overlies thaw-sensitive permafrost, some form of structural or operational adaptation may be needed to deal with permafrost thawing, and there is evidence that some adaptive measures are already being undertaken (Section 4.4). An important issue for the mining industry is the containment of wastes. Historically, the industry has relied on the impervious nature of permafrost to ensure long-term storage, but future permafrost thaw could eliminate the option of such surface-storage approaches and require remediation of older storage sites. In the case of the oil and gas industry, changing climate will affect exploration, production and delivery. Projected reductions in sea-ice cover, for example, are likely to be beneficial to exploration and development in both the energy and mining sectors, leading to further economic development.

Reductions in the thickness and seasonal extent of river, lake and sea ice will require adaptation of marine and freshwater transportation activities. These will vary from changes in the types of vessels used and the routes followed to a shift to more barge- and land-based traffic as ice roads and crossings become less viable. For the marine system, increases in navigability also raise important issues about the international use of the Northwest Passage. Expansion of marine and land-based transportation would have synergistic effects on resource exploration, as previously remote resources would become more accessible and economically viable to exploit. These changes will introduce new risks and opportunities for human settlements. The influx of wage employment may enhance adaptive capacity to some climate impacts; however, greater involvement in full time jobs will continue to be associated with current trends of social and cultural erosion.

Changes in habitat quality and quantity in the fisheries and forestry sectors will require adaptation ranging from shifts in management strategies to alterations in the equipment used. For both sectors, there are also concerns about how to deal with invading species and changes in biodiversity. Modified sustainable management plans will be required for both sectors to deal with future changes in climate. Key Arctic wildlife species at their southern limits are already being affected by changing climate, and alterations in management regimes and potential changes in boundaries of protective areas may be required. Actions to better understand and protect genetically unique and sensitive species that have undergone recent significant declines, such as the caribou herds of the central and western Arctic, will help support the health and cultural well-being of Aboriginal Arctic populations.

The direct health impacts of climate extremes and natural disasters are most significant for communities and individuals living in more environmentally exposed locations (e.g. remote, low-lying coastal areas and isolated mountainous regions), which are situated farther from emergency health services and with less developed emergency preparedness plans. Elders and those individuals with an already challenged health status are most vulnerable to temperature extremes. Many of the populations most highly exposed to the indirect impacts of climate change are already under stress from other forms of change, so the specific role of climate is often difficult to isolate. Based on increased exposure to untreated water sources and challenges in the effective use of municipal treatment systems in some small communities, these settlements are more vulnerable to the effects of warming on drinking water quality. However, large communities also face risks to water quality and supply because the access, treatment and distribution of drinking water is generally dependent upon a stable platform of permafrost for pond or lake retention, a situation that is currently changing.

Communities and households most vulnerable to the effects of climate change on food security are those that depend on a limited number of country/traditional food species, are high consumers of country/traditional foods, are located farther from regional centres and have limited access to market foods. Many of these communities also lack the economic resources to purchase new and more powerful hunting and transportation equipment to adapt to changing environmental conditions. Adaptation measures in the form of intercommunity trade programs, community freezers and a variety of individual behavioural changes have been developed by some communities to reduce the impacts already being experienced.

The political, cultural and economic diversity of northern Canada means that communities are affected by, and respond to, environmental change in different ways. For many of the currently identified climate-related impacts, it appears that the larger municipalities and their residents are less vulnerable than smaller, more remote communities. Larger municipalities are   generally less exposed to climate risks, and have greater capacity to adapt (e.g. greater access to economic resources, technology, infrastructure and health services). At the same time, however, groups and individuals residing within regional centres are dependent upon municipal infrastructure, which is sensitive to climatic change. Within the smaller, predominantly Aboriginal communities, many other factors influencing adaptive capacity are stronger, including traditional knowledge and skills, social capital, and risk perception and awareness. As vulnerability is a function of exposure and the ability to adapt, and these concepts vary within and between communities for particular climate-related impacts and opportunities, it is not possible to generalize climate change vulnerability across the Canadian North.

It is evident that the Canadian Arctic is already undergoing significant changes in climate, and that these changes are affecting almost every aspect of the northern environment and population. Many communities have already begun adapting. However, knowledge gaps remain regarding the thresholds at which impacts occur, how best to support ongoing adaptation efforts, where adaptation is not possible, and what the limits to adaptation strategies are for various locations and groups. Strengthening understanding in these areas will support more informed decision-making on these issues in future.