Status and Trends of the Nation's Biological Resources - Harvest

T his volume contains a variety of chapters about the demonstrated and suspected effects of natural and human-related agents on biodiversity. The effects of human-related agents may be indirect (such as habitat or climate change) or inadvertent—perhaps even the result of well-inten-tioned efforts to preserve biodiversity, such as the isolation of nature preserves or the potential for disturbance caused by ecotourism. Although nonconsumptive use of wild species has increasingly become a focus for exploitation by humans, this chapter explores the direct effects of con-sumptive exploitation—harvest—on biodiversity. Humans have long harvested, for commerce and for sport, many kinds of wild species from many different environments. Yet, as some human societies rethink their relations with other animal species (Scheffer 1976), the potential effects of harvest have become an increasingly contentious issue in the late twentieth century. Much has been written about the effects of harvest, though the distinction between ethical and scientific arguments is frequently blurred (Decker et al. 1991). This chapter deals with some of the principal scientific arguments about the effects of harvest on biodiversity and skirts the ethical ones, if only because science, as a way of learning and improving the reliability of knowledge, might indirectly inform ethics, values, and Historically, the scientific arguments about the effects of harvest on biodiversity revolved around how harvest affected the abundance or persistence of populations of single species, issues that still dominate the scientific literature and the day-today activities of many agencies charged with the management of natural resources. It is widely acknowledged, however, that we have little reliable information about the effects of harvest on wild populations. To improve our knowledge, we need a fundamentally new relation between the science and management of natural resources—namely, adaptive management biodiversity is exceedingly more complex than the most complex single population, so it follows that the potential effects of harvest on biodiversity must be exceedingly more complex. Because such complex issues cannot be dealt with in their entirety in this chapter, I focus on a few examples across several levels of biological structure from genes to populations and to ecosystems. I show that harvest exploitation necessarily alters some aspects of biodiversity. Thus, by extension, even noncon-sumptive exploitation that indirectly, yet effectively, " removes " or prevents organisms from normal interactions in populations must also alter biodiversity. At the end of the chapter, I discuss the much more contentious issue about whether such change actually …