The Regional Impacts of Climate Change

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Food and Fiber: Production Forestry (Section 8.3.5). The most intensively managed industry and private forestlands may be least at risk of long-term decline from the impacts of climate change because the relatively high value of these resources is likely to encourage adaptive management strategies. Private forest managers have the financial incentive and the flexibility to protect against extensive loss from climate-related impacts. They can use several available techniques: short rotations to reduce the length of time that a tree is influenced by unfavorable climate conditions; planting of improved varieties developed through selection, breeding, or genetic engineering to reduce vulnerability; and thinning, weeding, managing pests, irrigating, improving drainage, and fertilizing to improve general vigor. Such actions would reduce the probability of moisture stress and secondary risks from fire, insects, and disease. However, the more rapid the rate of climate change, the more it may strain the ability to create infrastructure for seeding or planting of trees, or to support the supply of timber if there is a large amount of salvage. A fast rate of warming also may limit species constrained by slow dispersal rates and/or habitat fragmentation, or those that are already stressed by other factors, such as pollution.

Food and Fiber: Fisheries and Aquatic Systems (Section 8.3.6). Aquatic ecosystem functions will be affected by climate change, although the effects are likely to vary in magnitude and direction depending on the region.

Projected increases in water temperature, changes in freshwater flows and mixing regimes, and changes in water quality could result in changes in the survival, reproductive capacity, and growth of freshwater fish and salmonid and other anadromous species. In larger, deeper lakes-including the Great Lakes and many high-latitude lakes-increases in water temperature may increase the survival and growth of most fish species. In smaller, mid-latitude lakes and streams, however, increased water temperatures may reduce available habitat for some cold-water and cool-water species. Increased production rates of food (e.g., plankton) with warmer water temperature (e.g., plankton production increases by a factor of 2-4 with each 10�C increase) also may increase fish productivity. However, shifts in species composition of prey with warming may prevent or reduce productivity gains if preferred prey species are eliminated or reduced. Warmer freshwater temperatures and changes in the pattern of flows in spawning streams/rivers could reduce the abundance of salmon, although individual size may increase from improved growth in the warmer water. Increases in temperature in freshwater rearing areas and increased winter flows may increase mortality for stocks in southern rivers on the west coast.

Freshwater species distributions could shift northward, with widespread/subregional species extinction likely at the lower latitudes and expansion at the higher latitudes of species ranges. For example, a 3.8�C increase in mean annual air temperature is projected to eliminate more than 50% of the habitat of brook trout in the southern Appalachian mountains, whereas a similar temperature increase could expand the ranges of smallmouth bass and yellow perch northward across Canada by about 500 km. Whether fish are able to move or will become extinct in response to changes in or loss of habitat will depend on the availability of migration routes.

Recreational fishing is a highly valued activity that could incur losses in some regions resulting from climate-induced changes in fisheries. The net economic effect of changes in recreational fishing opportunities is dependent on whether the gains in cool- and warm-water fish habitat offset the losses in cold-water fish habitat. The loss of fishing opportunities could be severe in some parts of the region, especially at the southern boundaries of fish species' habitat ranges. Although gains in cool- and warm-water fishing opportunities may offset losses in cold-water fishing opportunities, distributional effects will cause concern.

There will likely be relatively small economic and food supply consequences at the regional/national level as a result of the impacts on marine fisheries; however, impacts are expected to be more pronounced at the subregional and community levels. The adaptability of fisheries to current climate variability and the relatively short time horizons on capital replacement (ships and plants) will minimize the regional- and national-level impacts of projected climate change. At the subregional and community levels, however, positive and negative impacts can be significant as a result of suggested shifts in the centers of production and ensuing relocation of support structures, processors, and people.

Projected changes in water temperatures, as well as salinity and currents, can affect the growth, survival, reproduction, and spatial distribution of marine fish species and the competitors and predators that influence the dynamics of these species. Growth rates, ages of sexual maturity, and distributions of some marine fish species are sensitive to water temperatures (e.g., cold temperatures typically result in delayed spawning, whereas warm temperatures result in earlier spawning), and long-term temperature changes can lead to expansion or contraction of the distribution ranges of some species. These changes generally are most evident near the northern or southern species boundaries (i.e., warming resulting in a distributional shift northward, and cooling drawing species southward).

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