Adaptation and mitigation are sometimes treated as mutually exclusive approaches for dealing with global warming, but it is now acknowledged that they can be pursued jointly and that there are tradeoffs between them. A critical policy issue is the determination of which mix of adaptation and mitigation measures will maximize the benefits of efforts to reckon with climate change. Unfortunately, much less is known about how to adapt to that change than how to mitigate it. Despite this fact, the developed and developing countries have a mutual interest in devising adaptive responses, even if agreement on mitigation strategies remains elusive.
There is now reasonable scientific consensus that the continued loading of the atmosphere with radiatively active trace gases such as carbon dioxide, methane, nitrous oxide, chlorofluorocarbons (CFCs), and other gases will cause the troposphere (the lower portion of the atmosphere) to warm. As a consequence of this warming, climatic conditions throughout the world would change; less certain is the nature of these changes and where they would occur. Still less certain are the rate at which the atmosphere might warm, the attendant rate of change in climatic conditions, whether transient climate changes will occur (for example, cooling in a locale before it warms), and whether climate might change so that the frequency and severity of extreme events—such as droughts, storms, floods, and freezes—might be altered. Despite these uncertainties, it is highly likely that greenhouse-forced warming could have significant impacts on water resources, unmanaged ecosystems, agriculture, forestry, and fisheries, and on the societies and economies dependent upon them. Although the impacts likely would be beneficial in some regions, there is a serious risk that the world as a whole might be considerably worse off. Prudence argues that we should mitigate or eliminate the risk of climate change, if we can.
Scientists are experimenting with different types of soybeans to determine which ones are best adapted to specific climate conditions
However, atmospheric science also makes it clear that some amount of greenhouse warming is probable in the next century. The warming potential of the greenhouse gases that have already accumulated in the atmosphere has probably not been fully expressed because of the great capacity of the oceans to absorb heat before they warm noticeably. Hence, even if emissions of greenhouse gases were reduced quickly enough to avoid further accumulation of them in the atmosphere, some additional warming would be likely. If even in the best of cases we cannot totally avoid greenhouse warming and consequent climate change, prudence suggests that we look for ways to adapt to whatever the change may be.
Since we probably cannot avoid some amount of greenhouse warming, prudence suggests that we look for ways to adapt to the consequent climate change.
Adaptation and mitigation are sometimes treated as mutually exclusive approaches for dealing with global warming, and arguments in support of one approach may be treated as threats by advocates of the other. In a 1987 article, "Global Climate Change: Toward a Greenhouse Policy," in Issues in Science and Technology, Jessica Matthews described "adaptionists" as those who emphasize learning to live with greenhouse warming, and "preventionists" as those who emphasize the need to slow and eventually halt warming. This schismatic classification is, we believe, a misreading of the relationship. Surely few adaptionists, if any, believe that permanently increasing warming would pose no threat to global society. And surely the most committed preventionist, if convinced that some warming is inevitable, would deem it incumbent upon government to undertake adaptive action to reduce the consequent threats to life and property.
That the adaptation/mitigation argument has progressed from the either/or stage is evidenced in a number of ways. Scientists attending the second World Climate Conference held in Geneva, Switzerland, in November 1990 recognized the need for research to strengthen our understanding of the potential impacts of climate change and of ways to adapt to it. Another manifestation is the creation within the executive branch of the U.S. government of the committee on Mitigation and Adaptation Research Strategies (MARS) to coordinate interagency activities on those strategies.
Finding the right mix
Adaptation and mitigation policies are simultaneously complements and substitutes. The policies are complements in the sense that they can be, and should be, pursued jointly. They are also substitutes, meaning that there are tradeoffs between them as policies for dealing with global warming. Many, if not most, of the resources that could be devoted to the development of adaptive responses to climate change could also be devoted to pursuit of mitigation. The more resources that are devoted to one course, the fewer available for the other.
Technical advances like this automatic weather station, which guides irrigation scheduling, could help save water when supplies are short, as they may be if the climate changes
As an economic issue, the critical question is: What are the costs and benefits of alternative levels of effort devoted to the two courses of action? The benefits are the social values of damages averted; costs are the social values of the resources devoted to the aversion effort that could have been turned to some other purpose. Many of the costs and benefits could be expressed in dollars—for example, the value of the labor and capital used to build barriers against a rise in sea level. Other costs and benefits, however, could not be adequately expressed in dollars—for example, the loss of ecological values in unmanaged forests or the community values preserved where successful adaptation permits continued farming in a region disadvantaged by climate change. The nonquantifiable costs and benefits likely would be of major importance. Despite the uncertainty about them, they must be taken into account in thinking about the relative merits of adaptive and mitigative responses to climate change.
Whatever the answers to the economic question, the critical policy issue is to find the mix of adaptation and mitigation measures that maximizes the net social benefits of efforts to deal with climate change. This policy mix defines the total amount of resources that should be devoted to dealing with climate change, and also the socially optimum allocation of resources between adaptation and mitigation.
The outcome of this assessment of the relative merits of adaptation and mitigation strategies would not be as tidy as the foregoing statement might suggest. The great uncertainty about the costs and benefits of the two approaches, and the political struggle among the various interests with a stake in the outcome, assure that choices about the mix of strategies would be anything but clearcut. The point here is that however fuzzy the decision-making process, the choices should reflect recognition that because there are tradeoffs between adaptation and mitigation, the concept of an optimum mix of the two approaches is meaningful.
Two kinds of adaptive response
It is also important to recognize that there are two kinds of adaptive response to climate change, to which we now turn. One response includes all those things people would be induced to do within the existing institutional and policy regime. The other consists of institutional and policy changes that would be called for where and when the existing regime proved inadequate to deal with the impacts of climate change. The distinction is important because the resources available to undertake changes in institutions and in policies are always limited. These resources can be conserved to the extent that adaptations undertaken within the existing institutional and policy regime are successful.
Examples of the two kinds of adaptive response to climate change can be found in agriculture. Studies of the impacts of climate change on agriculture show that in many areas, including the U.S. Midwest, crop yields (output per acre) might fall with higher temperatures and less precipitation. The fall in yields would increase production costs to farmers, inducing them to investigate existing technologies and management practices for better ways to adapt to the changed climate. Farmers might turn to conservation tillage, a technique that conserves more soil moisture than the more commonly used tillage techniques. They might also adopt already available crop varieties that are better adapted to the hotter and drier climate, and invest in irrigation to counter the decline in precipitation. All of these adaptations are examples of measures that people would be induced to undertake within the existing institutional and policy regime.
However, in some circumstances these induced adaptations may be judged inadequate in the sense that after they have been made, society appraises the remaining costs of climate change as unacceptably high. In such a case, institutional or policy changes would be called for to develop additional adaptations that would bring the remaining costs within acceptable limits.
If farmers find that the alternatives available to them from among existing technologies and management practices are inadequate to compensate for the negative impacts of climate change, they may face the prospect of going out of farming, and perhaps leaving a region altogether. This prospect could stimulate agricultural research institutions and those charged with responsibility for agricultural policy to invest more in research to develop a new set of technologies and practices better adapted to the changed climatic regime. Institutional rules for allocating irrigation water might also be changed to give farmers greater flexibility in using water on their own farms and in transferring it among farms.
Researchers at Resources for the Future projected climate conditions of the dust bowl years on Missouri, Iowa, Nebraska, and Kansas to study the potential impacts of and response to climate change in those states
Prospects for adaption
The power of adaptation to offset negative consequences of climate change, or to permit exploitation of favorable consequences, has been little studied. It is likely that adaptive responses would be powerful in some circumstances and weak in others. A study conducted by Resources for the Future of the impacts of and responses to climate change in the four-state region of Missouri, Iowa, Nebraska, and Kansas showed that adaptations would significantly reduce the negative impacts of a hotter and drier climate on crop yields. RFF researchers projected climate conditions of the 1930s (the dust bowl years), which are consistent with predictions of hotter and drier weather produced by some climate models, on that region as it might be in 2030. Simulation models of plant growth indicated that, in the absence of adaptations, the production of corn, sorghum, and soybeans (three of the principal crops in the region) would be about 22 percent less in 2030 than if the climate did not change. When allowance was made for adaptations that farmers could make, including new technologies developed by research institutions, the simulation models showed a decline in production of corn (the most sensitive to climate change of the crops studied) of only 9 percent.
If adaptive responses within the existing institutional and policy regime prove inadequate, institutional and policy changes would be needed.
These results are, of course, speculative, but they are consistent with the history of the adaptability of farmers and of the ability of agricultural research institutions to respond to changing conditions of resource scarcity with which farmers must deal. The results are suggestive, therefore, of the power of adaptation in responding to climate change and of the importance of distinguishing between the two kinds of adaptive response.
In order to fully capture the benefits of the adaptive strategy to climate change, much more knowledge about the payoffs of various kinds of adaptation will be needed. The same could be said, of course, about mitigation strategies. But in at least one way adaptation is more complicated than mitigation. The physics of the greenhouse effect are understood, as are the ways to diminish the threat of global warming. Adaptation, however, raises a different set of problems stemming from the fact that we do not know how climate will change in any particular region and, hence, cannot know what the impacts of climate change will be. Regional climate changes are unpredictable as yet, and the prospects for improved predictability in the near term are poor. Thus the investment of great effort and resources now in developing specific adaptations to climate change for specific industries or infrastructures in specific regions would probably not pay off well.
One exception is adaptation to a rise in sea level, which will affect all of the world's shores, although not uniformly. As the atmosphere and (eventually) the seas warm, sea level will rise, threatening coastal areas around the world. But here, too, the possible rise in sea level is difficult to predict; estimates range from less than 0.5 meters to more than 1.5 meters during the course of the next century. In fact, it seems likely that the greatest impacts on land and people adjacent to the sea could be more the result of changes in wind force and direction than of a rise in sea level per se.
Finding a sensible adaptation strategy
What, then, is a sensible strategy for adapting to future changes in climate? First, we must gain a better understanding of the sensitivity and vulnerability of specific regions, industries, ecosystems, and societies to the normal range of climatic variability, and what can be done to diminish this sensitivity and vulnerability. For example, the North American Great Plains and many other regions of the world are subject to recurrent droughts. What technical and institutional measures can be applied to diminish the impacts of drought so that these regions can be made more resilient than they are today? Knowledge gained from answering this question would be directly applicable in the event that droughts in these regions become more severe or more frequent.
Better understanding how to reduce the vulnerability of specific regions to the normal range of climatic variability is the first step in a sensible adaptation strategy.
Second, research establishments should be working now to develop better responses to climate variability. Such research would produce many of the techniques needed for adaptation to climatic change because the primary threat of that change lies in more severe and more frequent extreme events.
Third, as knowledge of the dynamics of climatic change improves or as signs of change are perceived, or both, scientific and engineering resources should be assigned to the development of the specific adaptations needed. This would require, of course, that the scientific establishment remain capable of effective reaction from now until the time at which adaptations must be put into action.
The adaptive strategy might have a high payoff, and research to identify opportunities for adaptation and to provide knowledge and techniques needed to adapt would be a central part of that strategy. The developed countries seem well positioned to follow this strategy because their reliance on markets promotes flexibility in reallocating resources and their research establishments are strong. But what of the developing countries, with their smaller endowments of means and resources? Will they have the capacity to adapt as easily as the countries with higher per capita income?
There is no reason to believe that the developing countries, as a group, will be exposed to worse climatic changes than will the developed countries. It is certain, however, that their margin of survival would be smaller and that their opportunities for adapting to climatic change might be severely limited where the institutional and technical infrastructure, including research capacity, is weaker. In a paper entitled "Potential Strategies for Adapting to Greenhouse Warming: Perspectives from the Developing World" in the RFF volume Greenhouse Warming: Abatement and Adaptation (1989), N. S. Jodha, an agricultural economist from India, argues that farmers in developing countries use age-old techniques to cope in times of stress, and that these provide an arsenal from which to draw when climate change imposes a need for adaptation. Jodha provides many examples of the use of these techniques in India. There are exceptions, of course. In areas where agriculture is already risky because of severe climate or poor soils, particularly in the semiarid tropics, any detrimental climate change, however small or slow, can accentuate the risks and have serious impacts.
Because the developing countries are preoccupied with raising their currently low standards of living, they have shown relatively little interest in mitigating global warming. As Jodha shows, however, these countries, without necessarily having any greater interest in an adaptive strategy, nonetheless have accumulated substantial experience in adaptation, particularly in agriculture. Of course, the developing countries, like the developed countries, will need more knowledge of the prospective impacts of climate change and of possibilities for effective adaptive responses. There is a mutuality of interest here between developed and developing countries that may foster cooperative efforts in devising strategies for adaptation, even if agreement on strategies for mitigation remains elusive.
Pierre R. Crosson and Norman J. Rosenberg are senior fellows in the Energy and Natural Resources Division at RFF. Rosenberg is director of RFF' s Climate Resources Program.
A version of this article appeared in print in the May 1991 issue of Resources magazine.
A version of this article appeared in print in the May 1991 issue of Resources magazine.
