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Littoral and pelagic zones often are forgotten in studies of climate change impacts. However, important changes have already been observed (e.g., a significant increase in average temperatures of the waters in the western Mediterranean basin over the past 20-30 years) (Francour et al., 1994). Temperature changes are reflected in substantial changes in the relative abundance of thermophilic species; there have been increased catches of thermophilic fish species such as Diplodus cervinus, Epinephus marginatus, Pomadasys incisus, Sphyraena sphyraena, Balistes carolinensis, Sardinella aurita, and Pomatomus saltatrix.
Natural ecosystems may adapt to climatic change in one way or another-but not necessarily in ways preferred by humans. Therefore, some kind of human intervention, in the form of management, may be necessary. Adaptation options for forests and plants could include the creation of refugia; migration corridors and/or assisted migration; and improvements in integrated fire-, pest-, and disease-management techniques. This approach poses problems in many parts of Europe, where ecosystems have been so fragmented and the population density is so high that some of these options may be impossible to implement. Reforestation would be a viable adaptation option in some cases, as would afforestation of abandoned agricultural land-increasing habitats and establishing corridors between fragmented nature reserves. For wetlands and peatlands, reducing the impacts of climate change could be achieved through wetland restoration or creation techniques; in boreal regions where permafrost is a major feature of wetland ecosystems, however, such techniques would not be of much use. Freshwater biological systems can be assisted in a number of ways that could help mitigate the impacts of climate change, particularly through the increase and protection of riparian vegetation and the restoration of river and stream channels to their natural, adaptive morphologies. Such restoration processes may take several decades.
For all ecological systems, the reduction of pollution and land-use stresses in more heavily populated regions of Europe would contribute to removing major stress factors. In some circumstances, this strategy might allow plants to adjust more easily to the negative effects of climatic change.
An increasingly determined effort toward protection and revitalization of freshwater ecosystems in developed countries already has shown positive achievements, particularly through improvements in the water quality of watersheds. The protection of threatened aquatic habitats such as wetlands has facilitated the reintroduction of several endangered vertebrate species. This has been the case particularly in central Europe as a consequence of increased awareness of environmental problems.
The impacts of climate change on agriculture can be defined at different scales-including crop yield, farm or sector profitability, regional economic activity, or hunger vulnerability. Impacts depend on biophysical and socioeconomic responses.
In the past decade, substantial amounts of research have focused on regional and national assessments of the potential effects of climate change on agriculture. Relatively little work, however, has included systematic assessments that identify vulnerable socioeconomic groups, integrate effects across sectors, describe impacts at different spatial and temporal scales, or address the efficacy of the range of practical responses (see Parry et al., 1992). For the most part, studies have treated each region or nation in isolation (see IPCC, 1996, for a complete reference list of studies to date; see also Sirotenko et al., 1997), without regard to changes in production in other places, and have not addressed in an integrated way interactions with other related systems (e.g., water resources, socioeconomy, policy). Global assessments of climate change impacts in agriculture and agricultural markets have been few to date (Parry et al., 1988; Smit, 1989; Martin et al., 1990; Kane et al., 1992; Rosenberg and Crosson, 1991; UK Department of the Environment, 1991; Rosenzweig and Parry, 1994; Darwin et al., 1995). In addition, a major shortcoming of most climate impact assessments has been their lack of in-depth treatment of adaptation, in part because of its complexity and in part because of the lack of a suitable methodological framework.
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