which there are few property rights or for which economic value is only potential.
Some mitigative action is fully justified on other grounds. A good example is investments in energy efficiency that provide an excellent return on investment even with narrow economic calculations. Such actions can achieve the benefits of mitigation at no extra cost, while providing other benefits.
Many controversies are beginning to develop out of concerns with global change. One pits Third World countries against the developed countries that are now becoming concerned with limiting use of fossil fuels and restricting the felling of tropical forests. The Third World position, of course, is that other countries used fossil fuels and undeveloped frontiers for their economic development, and fairness dictates that the poorer nations now have their turn. Many analysts believe that if large-scale climate change results from human activities, the poorer countries are likely to suffer most because they lack resources they could use to adapt. Such an outcome would produce yet other conflicts.
The controversies about global change are only partly fact-based. True, some of the disagreements might fade with better knowledge about the global environment and the likely effects of different feasible responses. As it became clear that expected global warming over the next 50 years could not cause the breakup of the West Antarctic icecap, the flood-prevention rationale for slowing greenhouse gas emissions became considerably weaker. A response such as dike building seems much more appropriate when the sea threatens only a few areas. And if it became clear what each policy option—at the local, national, and international levels—would accomplish if enacted, some of them could easily be rejected.
But knowledge often fails to resolve controversy. It frequently raises new disputes or calls old beliefs into question. And even when new knowledge reduces uncertainty, controversies persist because not only facts, but also important interests and values, are at stake. Informed people disagree because the remaining uncertainty leaves room for judgment, because they may assume different scenarios about the future of society, and because an outcome that harms what one person values may enhance what another values. Those impressed with the potential benefits of economic growth tend to line up against those who fear of the