"Climate changes may have significant impacts on coastal stability, flood and storm hazards, and socio-economic activity or investment in the coastal zone." ⁽¹²⁾

As part of the Canada Country Study, coastal zone issues were addressed in the regional chapters of Atlantic Canada,⁽¹²⁾ British Columbia,⁽¹³⁾ the Arctic⁽⁶⁾ and Ontario.⁽¹⁴⁾ These chapters served to broadly define the potential impacts of climate change. The key findings of each with respect to the coastal zone are summarized below.

Sea level rise is a significant concern in Atlantic Canada, where most of the coast has been undergoing slow submergence for several thousand years due to non-climate factors.⁽¹²⁾ Global climate change would serve to accelerate the rate of sea level rise.

Major potential impacts include accelerated shoreline changes, flood hazards, storm damage and associated property loss, with utility (e.g., oil and gas) infrastructure and port facilities recognized as being particularly sensitive.⁽¹²⁾ Communities vulnerable at present to coastal erosion and storm-related flood and/or surge impacts would be at highest risk.

In the Canadian Arctic, higher air and water temperatures would lead to longer open water seasons and larger areas of open water, which in turn could result in intensified wave development, more frequent storm surges and increased coastal erosion and flooding.⁽⁶⁾ This would result in reduced coastal stability, which could be accelerated in some areas by permafrost degradation in the terrestrial component of the coastal zone. These impacts are expected to be most pronounced along the Beaufort Sea coast, including the Mackenzie Delta and Tuktoyaktuk Peninsula, where relative sea level is rising at present.⁽⁶⁾

On some reaches of Canada's west coast, climate change could result in increased erosion and/or sedimentation, as well as flooding of low-lying areas. Other potential impacts include loss of wetlands, changes in species distribution and abundance, and altered ecosystem structure. There also exists the potential for significant economic costs related to protecting coastal communities and beach nourishment, particularly in the greater Vancouver region.⁽¹³⁾

In the Great Lakes, average water levels could decline to record low levels during the latter part of this century.⁽¹⁴⁾ A drop in water levels would adversely affect commercial navigation and shore facilities by increasing the operating costs for ports and shipping channels in the Great Lakes- St. Lawrence Seaway system. Furthermore, changes in water temperatures, extent of seasonal ice cover and storminess would impact shoreline changes, ecosystems, infrastructure, and tourism and recreation in the Great Lakes coastal region.

Discussion of adaptation to climate change along marine coasts in the Canada Country Study centred around strategies of retreat, accommodation and protection, as promoted by the IPCC.^{(12, 13)} In most cases, impacts could be reduced by retreat or accommodation, whereas protection may require significant investment that may only be justifiable where significant fixed infrastructure is at risk.⁽¹²⁾ Examples of these three strategies are discussed later in this chapter.