"Roughly seven million Canadians live in coastal areas, where many people in smaller communities depend on the oceans' resources and tourism to make a living." ⁽¹⁾

Canada has more than 240 000 kilometres of ocean shoreline, more than any other country in the world.⁽²⁾ The coastal zone, broadly defined as near-coast waters and the adjacent land area, forms a dynamic interface of land and water of high ecological diversity and critical economic importance.⁽³⁾ Estuaries, beaches, dunes, wetlands and intertidal and nearshore zones support a diverse range of marine and terrestrial species and are key areas for fisheries and recreation. Coastal infrastructure is essential for trade, transportation and tourism, and is the lifeblood of many coastal municipalities. A similar interface extends along the shores of large lakes; for that reason, the Great Lakes, in particular, are often included in discussions of Canada's coastal zone.⁽⁴⁾ Comparable issues also arise in areas adjacent to other large Canadian lakes (e.g., reference 5).

Climate changes of the magnitude projected for the present century by the Intergovernmental Panel on Climate Change (IPCC) would impact the coastal zone in many ways. These include changes in water levels, wave patterns, the magnitude of storm surges, and the duration and thickness of seasonal ice coverage.⁽³⁾ Emphasis is commonly placed on water level changes because these would be extensive, though variable, throughout the coastal zone. Mean global sea level rise, resulting from thermal expansion of ocean waters and increased melting of glaciers and ice caps, will be the primary influence for water level changes along marine coasts.^(6,7) Water level changes along the shores of large lakes would relate to changes in regional precipitation and evaporation. For the Great Lakes, water levels are projected to decline over the coming decades as a result of climate change (reference 8; see Water Resources chapter).

Although there is strong scientific agreement that mean global sea level will continue to rise throughout and beyond the present century, there remains uncertainty regarding the magnitude of this change. Using a range of emission scenarios, the IPCC projects that global average sea level will rise between 9 and 88 centimetres in the period 1990 to 2100.⁽⁷⁾ This large range reflects both the output of future temperature scenarios and gaps in our knowledge of ocean and hydrological processes.⁽⁷⁾ It is also important to recognize that sea level rise will continue, and perhaps accelerate, in the following century due to the lag time between atmospheric temperature increases and ocean heating and glacier melting.

From an impacts and adaptation perspective, it is local changes in relative sea level that are important, and these can differ significantly from global changes. In addition to changes in climate, regional sea level changes are affected by geological processes of the Earth's crust and mantle that alter the relative position of land and sea. Changes in currents, upwelling, tidal range and other oceanic processes also influence relative sea level at the local level. For significant parts of Canada's Arctic coasts, sea level is currently falling in response to geological processes, whereas sea level is currently rising in other areas, including much of the Atlantic and Beaufort Sea coasts.⁽⁹⁾ The total amount of sea level change experienced at a particular location is a combination of all of these factors. Hence, not all areas of the country will experience the same rate of future sea level change.

An initial assessment of the sensitivity of Canada's coasts to sea level rise was presented by Shaw et al.,⁽¹⁰⁾ who concluded that more than 7 000 kilometres of coastline are highly sensitive, including much of the Maritime Provinces, a large part of the Beaufort Sea coast and the Fraser Delta region of British Columbia (Figure 1). Sensitivity is influenced by a variety of factors, including the geological characteristics of the shoreline (e.g., rock type, relief, coastal landforms) and ocean processes (e.g., tidal range, wave height). Whether the coastline is emerging or submerging at present is also extremely important in determining sensitivity to future climate changes.

Figure 1: Sensitivity of Canada's marine coasts to sea level rise larger image [JPEG, 105.5 kb, 600 X 544, notice]

The main physical impact of accelerated sea level rise would be an intensification of the rates of shoreline change that occur in the coastal zone at present. Processes such as beach erosion and retreat, bluff erosion and landward migration of barrier islands would continue, although more rapidly and extensively.⁽⁹⁾ Other major concerns include the inundation of coastal lowlands and an increase in storm-surge flooding. These changes could result in a suite of biophysical and socio-economic impacts on the coastal zone (Figure 2) that would ultimately impact a range of sectors, including fisheries, transportation, tourism and recreation, and communities.

Figure 2: Potential biophysical and socioeconomic impacts of climate change in the coastal zone (modified from reference 3)

The decline of Great Lakes water levels as a result of climate change would significantly impact coastal communities, infrastructure and activities. While some impacts may be beneficial (e.g., wider beaches, less flooding), many will be negative. For example, lower lake levels could necessitate increased dredging of marinas and ports, reduce shipping opportunities and affect water supplies of shoreline municipalities.⁽¹¹⁾

Human response and our capacity to adapt will play a large role in determining the vulnerability of the coastal zone to climate change. This chapter examines the potential impacts of climate change on Canada's marine and Great Lakes coastal regions, focusing primarily on issues related to infrastructure and communities. The discussion of potential adaptation options highlights the complexity of issues facing resource managers and communities in this unique setting. Reflecting the literature available, emphasis is placed on physical impacts, while recognizing the need for increased research on the potential social and economic impacts of climate change. The wide range of biological and ecological concerns that climate change could present for the coastal zone are discussed primarily in the Fisheries chapter of this report.