Conclusions

Coping with Global climate Change: The Role of Adaptation in the United States

As the climate-change research and policy communities fully confront the challenges of understanding and managing adaptation to climate change, the issues framed in this report provide important insight concerning the information needed to make appropriate policy choices regarding adaptation. The following conclusions provide initial guidance to those communities:

1. Adaptation and mitigation are necessary and complementary for a comprehensive and coordinated strategy that addresses the problem of global climate change. By lessening the severity of possible damages, adaptation is a key defensive measure. Adaptation is particularly important given the mounting evidence that some degree of climate change is inevitable. Recognizing a role for adaptation does not, however, diminish or detract from the importance of mitigation in reducing the rate and likelihood of significant climate change.
   
   
2. The literature indicates that U.S. society can on the whole adapt with either net gains or some costs if warming occurs at the lower end of the projected range of magnitude, assuming no change in climate variability and generally making optimistic assumptions about adaptation. However, with a much larger magnitude of warming, even making relatively optimistic assumptions about adaptation, many sectors would experience net losses and higher costs. The thresholds in terms of magnitudes or rates of change (including possible non-linear responses) in climate that will pose difficulty for adaptation are uncertain. In addition, it is uncertain how much of an increase in frequency, intensity, or persistence of extreme weather events the United States can tolerate.
   
   
3. To say that society as a whole “can adapt“ does not mean that regions and peoples will not suffer losses. For example, while the agricultural sector as a whole may successfully adapt, some regions may gain and others may lose. Agriculture in many northern regions is expected to adapt to climate change by taking advantage of changing climatic conditions to expand production, but agriculture in many southern regions is expected to contract with warmer, drier temperatures. Individual farmers not benefiting from adaptation may lose their livelihood. In addition, other individuals or populations in these and other regions can be at risk, because they could be adversely affected by climate change and lack the capacity to adapt.  This is particularly true of relatively low-income individuals and groups whose livelihoods are depending on resources at risk by climate change.
   
   
4. Adaptation is not likely to be a smooth process or free of costs. While studies and history show that society can on the whole adapt to a moderate amount of warming, it is reasonable to expect that mistakes will be made and costs will be incurred along the way. People are neither so foolish as to continue doing what they have always done in the face of climate change, nor so omniscient as to perfectly understand what will need to be done and to carry it out most efficiently. In reality, we are more likely to muddle through, taking adaptive actions as necessary, but often not doing what may be needed for optimal or ideal adaptation. Additionally, adaptation is an on-going process rather than a one-shot instantaneous occurrence.  Compounding society’s shortcomings, a more rapid, variable, or generally unpredictable climate change would add further challenges to adaptation.
   
   
5. Effects on ecosystems, and on species diversity in particular, are expected to be negative at all but perhaps the lowest magnitudes of climate change because of the limited ability of natural systems to adapt. Although biological systems have an inherent capacity to adapt to changes in environmental conditions, given the rapid rate of projected climate change, adaptive capacity is likely to be exceeded for many species. Furthermore, the ability of ecosystems to adapt to climate change is severely limited by the effects of urbanization, barriers to migration paths, and fragmentation of ecosystems, all of which have already critically stressed ecosystems independent of climate change itself.
   
   
6. Institutional design and structure can heighten or diminish society’s exposure to climate risks. Long-standing institutions, such as disaster relief payments and insurance programs, affect adaptive capacity. Coastal zoning, land-use planning, and building codes are all examples of institutions that can contribute to (or detract from) the capacity to withstand climate changes in efficient and effective ways. 
   
   
7. Proactive adaptation can reduce U.S. vulnerability to climate change. Proactive adaptation can improve capacities to cope with climate change by taking climate change into account in long-term decision-making, removing disincentives for changing behavior in response to climate change (such as removing subsidies for maladaptive activities), and introducing incentives to modify behavior in response to climate change (such as the use of market-based mechanisms to promote adaptive responses). Furthermore, improving and strengthening human capital through education, outreach, and extension services improves decision-making capacity at every level and increases the collective capacity to adapt.