In evaluating the implications of climate change impacts on North America, one must consider that although there are regional differences in response by sector and by subregion, the scale of anticipated changes is such that there may be adjustments taking place in every sector and subregion simultaneously. Any one of the impacts (whether beneficial or detrimental) that has been discussed for North America may appear well within the capability of existing structures and policies to adapt. However, the fact that they are occurring simultaneously may pose a significant challenge to resource managers and policymakers. The systemic nature of impacts and issues raises important questions about society's ability to manage the aggregate/cumulative risks posed by climate change.
This systemic problem also must be placed into the larger context of the multiple stressors that are and will be acting on North American resources. Many stressors (environmental, social, and economic) influence natural and human systems and pose significant challenges for decisionmakers and policymakers. The challenge of coping with the cumulative risks of climate change adds to the complexity. What must be kept in mind is that changing climate is not the only-nor necessarily the most important-factor that will influence these systems and that it cannot be isolated from the combination of other factors determining their future welfare.
A complete assessment of the effects of climate change on North America must
include a consideration of the potential interactions and feedbacks between
sectors and subregions. Changes in the climate system can affect natural and
human systems in a chain of consequences (see Figure 8-12).
Some of these consequences are the results of direct effects of climate change
and variability on physical, biological, and socioeconomic systems; some result
from indirect links between climate-sensitive systems and related social and
economic activities; some result from feedbacks between human activities that
affect the climate system, which in turn can lead to further impacts (e.g.,
human activities affecting the climate system-which, in turn, can lead to further
impacts on human health, the environment, and socioeconomic systems).
|Figure 8-12: Chain of consequences.|
Most existing studies of potential impacts have focused on the more narrow direct pathway between climate change and climate-sensitive systems and sectors. These effects include direct climate impacts on human health (e.g., heat stress), environmental processes (e.g., impacts of runoff and streamflow on the hydrological cycle, coastal damages caused by sea-level rise, changes in biodiversity), market activities that are linked to the environment (e.g., agriculture, commercial timber, waterborne transport), and human behavior (e.g., changes in air conditioning use as a result of changes in the frequency of very hot days).
Fewer studies have captured the more indirect effects of climate change, which may take many different forms. Many of the primary determinants of human health (adequate food, clean water, secure shelter) are related to outputs from sectors such as agriculture, water resources, and fisheries. The potential spread of infectious diseases is indirectly related to climate change through changes in ecosystems and the hydrological cycle. Therefore, it is important to integrate these relevant systems into a human health assessment.
Other indirect effects include secondary impacts on market activities that are dependent upon sectors directly affected by climate change. For example, climate change will directly affect crop yields and hence agricultural production and prices. These effects, in turn, will influence the prices of goods and services that use agricultural commodities in their production, which will feed back to the agricultural sector and agricultural prices. Shifts in agricultural production could have a large impact on freight transport patterns and may require adjustments in the transportation network-with marine, road, rail, and air links potentially needing expansion into areas not currently serviced. One study of the U.S. economy suggests that the direct effects of climate change on U.S. agriculture, energy use, and coastal protection activities could lead to price increases for all economic sectors, causing a reallocation of spending and the sectoral composition of output.
Other indirect effects include changes in nonmarket activities as a result of projected impacts of climate change on ecosystems (e.g., changes in recreational fishing as a result of projected impacts of climate change on aquatic ecosystems). For example, the loss of fishing opportunities could be severe in some parts of the region, especially at the southern boundaries of fish species' habitat regions. The loss of fishing opportunities may result in economic losses for the fishing industry. In turn, related industries such as the food, transportation, and lodging industries will be affected. All of these examples illustrate how each sector that is directly or indirectly affected by climate change can adversely affect others.
As this chain of consequences illustrates, the task of assessing various impacts and the feedbacks among them is enormously complex and requires a number of simplifying assumptions. Although there are complex macroeconomic models to assess the costs and consequences of various mitigation policies, the state of the art in impact work at present limits the insights that can be gained from this kind of "top-down" modeling. The dominant approach has been "bottom-up"-aggregating direct and indirect impacts into a single overall estimate, without much attention to feedbacks among various sectors. Nevertheless, the complex, integrated nature of the climate change problem suggests the need for integrated assessments that incorporate many aspects of the region. Sectoral assessments alone would not be sufficient.
Examples of broad, integrated approaches to climate impact assessment are two
regional studies in North America: the Mackenzie Basin Impact Study and the
Great Lakes-St. Lawrence Basin Project.
The Mackenzie Basin Impact Study (MBIS) was a 6-year climate change impact assessment focusing on northWestern Canada (supported by Environment Canada and other sponsors) to assess the potential impacts of climate change scenarios on the Mackenzie Basin region, its lands, its waters, and the communities that depend on them (Cohen, 1997a). The MBIS was designed to be a scientist-stakeholder collaborative effort, with 30 research activities on various topics-ranging from permafrost and water levels to forest economics and community response to floods.
The MBIS integration framework included several integration modeling
exercises-such as resource accounting, multiregional input-output modeling
and community surveys of the nonwage economy of an aboriginal community,
a multiobjective model focusing on scenarios of changing land utilization,
and a land assessment framework (ILAF) with goal programming and an analytic
hierarchy process. MBIS researchers identified six main policy issues
related to climate change as another form of "vertical integration": interjurisdictional
water management, sustainability of native lifestyles, economic development
opportunities, buildings, transportation and infrastructure, and sustainability
of ecosystems (Cohen, 1997a). Integration also was attempted through information
exchange (scenarios and data) while study components were in progress
and a series of workshops that provided opportunities for scientists and
stakeholders to express their views on how climate change might affect
the region and to react to research results (Cohen, 1997a,b).
The main result of the integrated assessment was that most participating stakeholders saw climate impacts scenarios as a new and different vision of the future for their region, and that adaptation measures alone might not be enough to protect the region from adverse impacts.
These two efforts have tried to account for some of the synergies and interactions
among sectors that make each region unique. Each represents a learning experience
that ultimately will lead to improvements in how regional assessments and integration
|The Great Lakes-St. Lawrence Basin (GLSLB) Project on "adapting to the impacts of climate change and variability" is a binational project initiated in 1992 by Environment Canada to improve our understanding of the complex interactions among climate, environment, and society so that regional adaptation strategies could be developed in response to potential climate change and variability (Mortsch and Mills, 1996). The GLSLB Project identified four climate-sensitive theme areas upon which to focus the research: water use and management, land use and management, ecosystem health, and human health. Another prime focus of the GLSLB Project is adaptation, which provides the conceptual framework for integrating research efforts. GLSLB Project studies contain common components that will facilitate the integration of research findings, including study objectives; policy issue foci; a multidisciplinary approach; scenarios tested; impact and adaptation assessment methods; the concept of adaptation; and scales of time, space, and human activity (Mortsch and Mills, 1996). A number of more pragmatic integration concepts also have been incorporated into the GLSLB Project, including the use of "end-to-end studies" assessing biophysical and socioeconomic impacts and developing and evaluating potential adaptation strategies, economic modeling (LINK model), the use of Geographic Information Systems (GIS), and common communication goals (Mortsch and Mills, 1996).|
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