ideology. Scientists know much about the technical changes that could mitigate China's greenhouse gas emissions, but they have relatively little quantitative understanding of the social factors that make possible, and interact with, technological change. Enough is known to identify some of the critical determinants of Chinese energy intensity, but not to quantify their effects or specify their interactions. That will require further research. For example, critical changes in policy, such as increased emphasis on market incentives and decentralized decision making, might greatly improve energy productivity. Studies of transitions to increased market control in other command economies might provide valuable knowledge for projecting the likely effects of such policy changes on energy efficiency in China. The future of Chinese energy demand also depends on changes in the structure of the Chinese economy and of consumer demand. Careful comparative studies of the social determinants of energy intensity and changes in energy intensity at the level of nation-states are critical for understanding and projecting China's future contribution to the greenhouse effect.
Clearing of tropical forests is generally considered to be the most important single cause of recent losses in the earth's biological diversity. It also accounts for about 15 percent of the effect of human greenhouse gas emissions. Clearing has been very extensive in recent years, and the disturbances are not readily reversible, as deforestation by indigenous slash-and-burn techniques had previously been (Conklin, 1954; Nye and Greenland, 1966; Sanchez et al., 1982). The damage is now so extensive and severe as to preclude regeneration to original cover without special measures that are only now being developed (Uhl et al., 1989).
The most widely used definition of biological diversity includes three levels: genetic, species, and ecosystem diversity (Norse et al., 1986; U.S. Office of Technology Assessment, 1987). Deforestation reduces diversity at all three levels. Genetic diversity, or the diversity of genes within a species, provides the raw material for evolution, as it allows some individuals of a species to survive environmental changes that prevent other individuals from living or reproducing. Species diversity, which refers to the many million species now estimated to exist on earth, is richest in the tropical forests, particularly in the Amazon Basin (Erwin, 1988). Many of the Amazonian species are closely tied to particular forest ecosystems and tree species, so that they are very narrowly