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6.1. Introduction and Scope
The oceans cover 70% of the Earth's surface and play a vital role in the
global environment. They regulate the Earth's climate and modulate global
biogeochemical cycles. They are of significant socioeconomic value as suppliers
of resources and products worth trillions of dollars each year (IPCC, 1998).
Oceans function as areas of recreation and tourism, as a medium for transportation,
as a repository of genetic and biological information, and as sinks for wastes.
These functions are shared by the coastal margins of the oceans.
Approximately 20% of the world's human population live within 30 km of
the sea, and nearly double that number live within the nearest 100 km of the
coast (Cohen et al., 1997; Gommes et al., 1998). Nicholls and Mimura (1998)
have estimated that 600 million people will occupy coastal floodplain land below
the 1,000-year flood level by 2100.
Any changes associated with global warming should be considered against the
background of natural variations, such as long-term variations caused by solar
and tectonic factors, as well as short- and mid-term changes related to atmospheric
and oceanic conditions. Climate change will affect the physical, biological,
and biogeochemical characteristics of the oceans and coasts at different time
and space scales, modifying their ecological structure and functions. These
changes, in turn, will exert significant feedback on the climate system. The
world's oceans already are under stress as a result of a combination of
factors—such as increased population pressure in coastal areas, habitat
destruction, and increased pollution from the atmosphere, from land-based sources,
and from river inputs of nutrients and other contaminants (Izrael and Tsyban,
1983). These factors, along with increased UV-B radiation resulting from stratospheric
ozone depletion, are expected to impair the resilience of some marine ecosystems
to climate change.
This chapter reviews the potential impacts of climate change on the coastal
zone, marine ecosystems, and marine fisheries. It provides an assessment of
the latest scientific information on impacts and adaptation strategies that
can be used to anticipate and reduce these impacts. Emphasis is placed on scientific
work completed since 1995. This chapter builds on earlier IPCC reports but differs
in several significant ways. First, the content of the present chapter was covered
in three separate chapters in the Second Assessment Report (SAR: Chapter 8,
Oceans; Chapter 9, Coastal Zones and Small Islands; Chapter 16, Fisheries) and
in two chapters in the First Assessment Report (FAR: World Oceans and Coastal
Zones, Working Group II; Coastal Zone Management, Working Group III). Second,
in the Special Report on Regional Impacts of Climate Change (IPCC, 1998), impacts
on the oceans and coasts were considered in each of the regional chapters; those
on the Small Island States and the Arctic and Antarctic were of particular relevance
to the present chapter. Third, whereas previous IPCC reports highlighted sea-level
rise, vulnerability assessment, biogeophysical effects, and single-sector impacts,
this chapter covers several other topics—including a range of methodologies;
climate-change parameters; physical, biological, and socioeconomic sensitivities;
and adaptation mechanisms. Additional and regionally specific coastal and marine
details are included in the regional chapters of this Third Assessment Report
(TAR).
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