"The world community faces many risks from climate change. Clearly, it is important to understand the nature of those risks, where natural and human systems are likely to be most vulnerable, and what may be achieved by adaptive responses" (Intergovernmental Panel on Climate Change, 2001).

Climate Change Impacts and Adaptation: A Canadian Perspective presents an overview of current issues in climate change impacts and adaptation in Canada, as reflected in research conducted over the past five years. The discipline has evolved significantly, as researchers from a wide range of disciplines have become increasingly involved. Enhanced interest reflects the growing realization that, even with effective mitigation measures, some degree of climate change is inevitable. Impacts are no longer viewed as hypothetical outcomes, but as risks that need to be addressed through adaptation. Indeed, as emphasized in the Third Assessment Report of the Intergovernmental Panel on Climate Change, adaptation is a necessary complement to reducing greenhouse gas emissions in addressing climate change at all scales.

Adaptation to climate change represents a challenge to all countries of the world, including Canada. Although climate change may be unique in its scope and the potential magnitude of its impacts, humans have always adapted to changes in their environment, both climatic and non-climatic, so there is a foundation of knowledge upon which to build. The purpose of adaptation is not to preserve the status quo, since that will simply not be possible for most ecosystems and many human systems. Rather, the goal of adaptation is to reduce the negative impacts of climate change, while taking advantage of new opportunities that may be presented. Since there will always be uncertainties associated with climate change, the issue is best addressed in the context of risk management.

An important shift over the past 5 to 10 years has been the growing recognition of the importance of considering social, economic and political factors, in addition to biological and physical ecosystem factors, in impacts and adaptation studies. For instance, preliminary studies have been conducted into the costs of both potential impacts and various adaptation options. There has also been increasing use of the concept of vulnerability in impacts and adaptation research. Vulnerability refers to the degree to which a system, region or sector is susceptible to, or unable to cope with, the effects of climate change and climate variability. Research focused on vulnerability emphasizes the need to develop a strong understanding of the current state of the system being studied by involving stakeholders and taking an integrative, multidisciplinary approach. Through consideration of current vulnerability, along with scenarios of future climate, social and economic conditions, it is possible to estimate future vulnerabilities in the context of risk management. Continued improvements in climate modelling and scenario development are important for impacts and adaptation research. Likewise, improved understanding of how adaptation occurs, and what barriers exist to successful adaptation, is extremely important.

The seven sectoral chapters of the report outline the potential impacts of climate change on key sectors of Canada's economy, providing a review of recent research and identifying knowledge gaps and research needs. Through this review, it is evident that climate change impacts, and our ability to adapt to those impacts, will differ both among sectors and among the various regions of Canada. These differences will depend largely on the factors that determine vulnerability, namely, the nature of the climate changes, the climatic sensitivity of the sector and its adaptive capacity. There will be benefits and challenges for all sectors. Comprehensive assessment of this net balance has not been completed and, indeed, may not yet be possible given existing knowledge gaps. Nonetheless, there is general consensus in the literature that negative impacts are expected to dominate for all but the most modest warming scenarios. This is especially true for certain sectors, such as health and water resources, and less so for others, such as transportation.

It is important to recognize that, although issues are presented on a sectoral basis in this report, many of these sectors are strongly interdependent. Therefore, impacts on, and adaptation decisions made in, one sector will often have implications for other sectors. This is especially evident in the case of water resources, where it is clear that many other sectors, including transportation, agriculture and fisheries, could be affected by decisions taken to address changes in water quantity and/or quality. It is also important to consider interactions among regions, both within Canada and globally, as losses or benefits in one region often have far-reaching consequences.

Although gradual changes in mean conditions would bring both positive and negative impacts, an increase in the frequency and/or intensity of extreme events would present challenges for most sectors. Extreme events already often fall outside of current coping ranges and cause critical thresholds to be exceeded. Systems that are currently under stress are generally considered to be at the greatest risk. Proactive and precautionary adaptive measures would help reduce losses associated with current climate variability, as well as increase resiliency to future changes in climate and extreme climate events. Enhancing adaptive capacity through a range of technological, regulatory and behavioural changes will bring both immediate and long-term benefits.