Conservation and toxicology: The need to integrate the disciplines

Global warming, ultraviolet radiation, and acid rain are large—scale environmental problems that concern conservation biologists. They are caused, to varying degrees, by humangenerated pollution, and consequently they are studied by environmental toxicologists. These problems seem to be the major areas of overlap between conservation biologists and environmental toxicologists. This limited overlap is probably the result of the disciplines involved. Scientists tend to specialize, not taking advantage of the ideas and information in other fields, and environmental toxicologists and conservation biologists focus on different levels of biological organization. We believe it is time for conservation biologists and environmental toxicologists to become more aware of their shared goals. Consider the statement of goals listed in the major journals of each field. Conservation Biology seeks “… to help develop the scientific and technical means for the protection, maintenance, and restoration of life on this planet—its species, its ecological and evolutionary processes, and its particular and total environment.” Environmental Toxicology and Chemistry is “… a forum for professionals in academia, industry, government, and other segments of society involved in the use, protection, and management of the environment for the enhancement of ecological health and human welfare.” These statements are actually quite similar. Yet the mention of conservation biology by environmental toxicologists or of environmental toxicology by conservation biologists is rare. In the past two years of Conservation Biology, only eight articles out of 394, or 2%, discussed pollutant—related environmental damage. Likewise, only 56 articles out of 560 in Environmental Toxicology and Chemistry, or 10%, discussed conservation issues relating to the effects of environmental contamination. These percentages are based on a liberal survey of the literature, wherein an article need only allude to the conservation implications of a toxicological study or the existence of a toxicological impact on conservation issues to be included. For example, mention of global warming in a conservation article even without the mention of the causes of global warming would result in inclusion in the above totals. One of the major interests of conservation biologists is conducting population viability analyses to determine the probability of extinction of populations or species. Essential to calculating extinction risk is the tenet that larger populations are at a lower risk of extinction [1]. Shaffer [2] pointed out that populations affected by environmental uncertainty and catastrophe require greater minimum population sizes to persist. Although conservation biologists typically are concerned with factors such as habitat destruction and fragmentation or the introduction of exotic species, chemical contaminants can cause major extinction events or may act subtly in concert with other factors to compound the probability of extinction. As a catastrophe, a large—scale event such as an oil spill, a nuclear accident, or the release of an untreated effluent can cause the immediate loss of entire populations. Though rare, these events can be included successfully into population viability analyses and endangered species management. Toxicologists and conservation biologists on the Southern Sea Otter Recovery Team developed a population viability analysis that included the probability of a large oil spill affecting the population size of otters off the coast of California [3]. The more subtle effects of contaminants can be included in population viability analyses and can take many forms. Of particular importance are sublethal and chronic effects, such as endocrine or immune system impairment or developmental delays. These effects can result in decreased reproductive success and/or decreased survival, both of which are classic fitness parameters that can be incorporated into viability analyses at the level of the individual or population. For example, Nisbet et al. [4] and Muller and Nisbet [5] developed a modeling approach that incorporates the response of individuals to toxicant exposure by linking a dynamic energy budget model of individual growth and reproduction, a toxicant bioaccumulation model, and a model of toxicant action on the individual. A different individual—based modeling framework incorporating the effects of contaminants on individuals was proposed by Hallam and Lassiter [6], and Belovsky [7] used a linear programming approach to incorporate the effects of pesticides on individual foraging behavior. At the population level, Meyer and Boyce [8] outlined an approach to incorporate the effects of contaminants into age- or stage—structured population projection models. Inclusion of contaminant issues in empirical conservation studies is also feasible. Kushlan [9] considered the potential sublethal effects that environmental contaminants may impose on wading birds. Ogutu—Ohwayo et al. [10] examined the effects of pollutants on fish in the African Great Lakes. Consequently, progress is being made to develop the theoretical and experimental tools to explicitly incorporate the field of toxicology into conservation. Good examples of successful incorporation of conservation issues into toxicological studies also exist. De Guise et al. [11], working on the Beluga whale population of the St. Lawrence Seaway, characterized the effects of environmental contaminants on immunological parameters. Despite the cessation of hunting, this endangered species continues to decline, with the putative cause being the adverse impact of pollution on their health. Another taxonomic group used in both conservation biology and environmental toxicology is freshwater mussels [12], which are used as indicators of water quality by conservation biologists. Pesticides are thought to play a role in the episodic die—offs and population declines experienced by many taxa. One of the most critical conservation problems is understanding the potential causes of amphibian decline in various regions around the globe. In the western United States, assessment of the exposure to and effects of UVB radiation [13], acidification [14], and pesticides [15] is contributing to conservation efforts on behalf of declining native amphibians. In light of the limited interaction between the two disciplines, we offer three suggestions for better integrating the two fields. (1) Conservation biologists should include contaminant effects explicitly in conservation modeling and research efforts. This could encompass consideration of risk of spills, subtle habitat degradation, and chronic toxicity impacts on life history parameters. Such consideration acknowledges that mechanisms acting below the level of the individual can be responsible for changes at the level of the population. (2) Environmental toxicologists should give specific consideration to species whose decline may be the result of exposure to contaminants. This indicates recognition that mechanisms operating below the level of the individual may have consequences for higher levels of organization. (3) Both groups should expend greater effort to develop scientists whose research programs integrate these two fields. Including toxicology in conservation curricula and enhancing toxicology with conservation studies can facilitate this. Integrating these two fields is crucial to meeting the longterm goals of each. Both have a primary interest in examining or preserving what Michael Soulé [16] termed the “long—term viability of the whole system.” Ignoring the effects of environmental pollutants will never allow for attainment of this goal by conservation biologists. Equally, failure of environmental toxicologists to make their work available to conservation biologists will obscure the value of their work as well.