10.2.3.2. Fisheries
Even without major changes in atmospheric and oceanic circulation, local shifts
in centers of production and mixes of species in marine and fresh waters are
expected as ecosystems are displaced geographically and changed internally.
The relocation of populations will depend on the presence of properties in changing
environments to shelter all stages of the life cycle of a species. Under climatic
warming, positive effects for saltwater fisheries-such as longer growing seasons,
lower natural winter mortality, and faster growth rates in higher latitudes-may
be offset by negative factors such as the alteration of established reproductive
patterns, migration routes, and ecosystem relationships. Changes in abundance
are likely to be more pronounced near major ecosystem boundaries. The rate of
climate change may prove to be a major determinant of the abundance and distribution
of new populations. Rapid change from physical forcing usually will favor production
of smaller, low-priced, opportunistic species that discharge large numbers of
eggs over long periods. Regionally, gains or losses in freshwater fisheries
will depend on changes in the amount and timing of precipitation, on temperatures,
and on species tolerances. For example, increased rainfall during a shorter
period in winter could lead to reduced summer levels of river flows, lakes,
and wetlands-and thus to reductions in freshwater fisheries. Marine stocks that
reproduce in freshwater (e.g., salmon) or require reduced estuarine salinity
will be similarly affected (IPCC 1996, WG II, Chapter 6 Executive Summary).
Aquaculture is particularly important to Temperate Asia. In 1994, the world's
aquaculture production was about 18.6 million tons (excluding seaweed), of which
Temperate Asia accounted for 64.7% and China alone accounted for 57.2% (FAO,
1996a). With seaweeds included, the world's production in 1994 was 25.4 million
tons, and the shares of Temperate Asia and China were 70.3% and 60.4%, respectively.
During the period from 1984 to 1994, aquaculture in Temperate Asia demonstrated
a yearly growth rate of 10% in volume and 11% in value (FAO, 1996b). Climate
change impacts generally will be positive through faster growth, lower winter
mortality rates, reduced ice cover, and reduced energy costs as a result of
expanded regions of warmer water. Cultivation of warm-water species also may
expand. Warming will require greater attention to possible oxygen depletion,
fish diseases, and introduction of unwanted species (IPCC 1996, WG II, Section
16.2.3).
10.2.3.3. Production Forestry
Projections for 2010 indicate that the need for industrial roundwood could
increase 38% (southern Temperate Asia) to 96% (eastern Temperate Asia). These
requirements may result in serious shortages of boreal industrial roundwood,
placing further stress on boreal forests (IPCC 1996, WG II, Section 15.4.3).
10.2.4. Coastal Systems
10.2.4.1. Sea-Level Rise
Current best estimates for sea-level rise-1.0-2.5 mm/yr-represent a rate two
to five times higher than that experienced in the past 100 years. Even with
assumed stabilization of global greenhouse gas emissions, sea level is projected
to continue to rise beyond the year 2100 because of lags in climate response.
Regional differences will exist as a result of wind and atmospheric pressure
patterns, regional ocean density differences, and oceanic circulation. For Temperate
Asia, sea-level rise is projected to be slightly below the global mean value
around the Okhotsk Sea and along the coasts south of about 30°N and slightly
above the mean elsewhere (IPCC 1996, WG II, Section 9.3.1).
Along most of the continental coast, relative sea level (i.e., sea level in
relation to land) is an important factor for coastal environments. Deltaic coasts
in China are facing severe problems of relative sea-level rise as a consequence
of tectonically and anthropogenically induced land subsidence. Sea-level rise
related to global warming will exacerbate these problems. In addition, saltwater
intrusion problems will become more serious with sea-level rise in deltaic regions
and coastal plains (IPCC 1996, WG II, Section 9.4.2).
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