Toxicity testing with communities: microcosms, mesocosms, and whole-system manipulations.

Present ecotoxicological methodology is not adequate for providing evidence for decisions on sustainable use of the planet, maintenance of ecosystem services, or ecosystem health. However, particularly in the area of ecosystem health, promising beginnings have been made. Presumably, if ecosystems are maintained in robust health, then sustainability and reliable delivery of ecosystem services should result. On the other hand, one cannot ignore either human population size or expectations of affluence. Whether the number of ecosystems in robust health will be adequate for appropriate delivery of ecosystem services not only for existing generations but for future generations still has very unacceptably high levels of uncertainty. All ecosystems are dynamic, and one of the problems will be distinguishing normal cyclical or successional changes from trends away from established norms. Furthermore, toxicity tests are extremely useful for determining deleterious effects and those concentrations at which no-observable-deleterious effects occur. They are not suitable for determining how successfully various materials are being reincorporated into natural systems without disturbing ecological integrity. In a very real sense, however, this is a toxicological problem because, like vitamins and other essential materials for humans, excessive amounts of at least some types can be deleterious as can other materials such as ordinary table salt. It seems inevitable that different criteria, standards, endpoints, and methodologies that revolve around sustainability, ecosystem services, and reincorporating extracted and manufactured materials into natural systems following their use by human society will be required. Furthermore, ecosystems are different, both structurally and functionally, in different climatic zones, different altitudes, different soil conditions, and the like. Therefore, widespread uniform standards seem unlikely to function well, particularly for toxic materials. Prescriptive legislation, as opposed to that requiring site-specific professional judgment, is not likely to serve well under these circumstances. How success will be determined, how deleterious effects will be supported by evidence, and how effective extrapolations from one system to another will be are just a few of the many questions that need resolution. Finally, both temporal and spatial scales of systems under examination must increase, as will the diversity of information used as a basis for professional judgment. All of these factors are occurring in other areas of human societies, increasing globalization, and entry into the information age. Thus, the trends for ecotoxicology are in many ways quite similar to those in other professions as well.