unlikely. Not only can these molluscs invade areas occupied by North American species, but they can also occupy habitats created by an industrial society, such as power plant cooling systems, irrigation canals, waste treatment ponds, and, in the case of the zebra mussel, surfaces such as ship hulls (e.g., Cherry et al., 1986; Garey et al., 1980; Hayward et al., 1982; Nalepa and Schloesser, 1993).

In addition to the problems caused in the technological portion of human society, there is also an increased risk to natural systems resulting from the marginally effective control measures designed to minimize the impacts of these species on the industrial system, including agro-industry. These invaders of North America have created chaos in both the technological and the ecological components of human society's life-support systems.

Thus, while there is ample cause for concern about biotic impoverishment (e.g., Wilson, 1988), there seems to be little concern about the ultimate consequences of this coevolutionary process. If the assumption is that humans are incapable of driving all species to extinction, those left will be highly adapted to exploit the new environmental conditions resulting from overemphasis on the maintenance of technological services. Pest species will be difficult to eradicate—those capable of invading habitats unsuitable for most other species; those selected for resistance to pesticides and other control measures; and, in many instances, those so intimately associated with human society (such as the Norway rat, the housefly, and the cockroach) that control measures may also be a risk to human health. However, failure to exercise the control measures may pose an equal danger to human health as a result of spread of disease.

Nonsuch Island provides excellent examples of the ability of exotic species to colonize, as do the Hawaiian Islands and many other island ecosystems. On Nonsuch, Wingate (1990) reported the necessity of a major and continuous effort to eliminate invading species. Plant invaders are brought to Nonsuch from other Bermuda islands by birds that feed there and then defecate the seeds and other propogules while roosting at night. Even reestablishing the species that existed on the islet before heavy colonization by Europeans would not enable that community to resist invasion by exotics if the sources of colonizing species were in either the conterminous or contiguous ecological landscape in which Nonsuch exists.

Although experimental evidence is not robust, one might still reasonably conclude that, once human society has created chaos in a natural system by destabilizing a complex system, the new system, whatever ecologists may think of it, is now a coevolutionary partner with human society. This plausible analysis provides grounds for persuading human society to consider the coevolutionary consequences of the impact of its technological life-support system on its natural life-support system.

The situation described as hostile coevolution is a form of "social trap." The social trap in this case is the feeling that any major change in human behavior will result in such chaos in the economic system that the natural systems will just have



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