What is “normal”? Defining baseline states of infection for ecosystems

Abstract

Until recently, natural resource managers treated infectious disease exclusively as a problem to be eliminated. But as science has clarified the role of parasites in ecosystems, it has become evident that some level of infection is “normal” in ecosystems, even necessary for ecosystem integrity. Now managers are confronted with a difficult task: identifying which parasite species are more abundant than they should be, which are less abundant than they should be, and why. In this chapter, the authors discuss the advantages of and outline strategies for defining baseline states of infection in ecosystems. They start with strategies for exploring what is “normal” for a particular parasite species of contemporary concern and continue with strategies for defining baselines when the entire parasite community is of interest. Developing baselines can provide managers with a target for infectious disease management that limits the destructive potential of some parasites and harnesses the power of others to improve ecosystem function, while providing insights into the ecological role of parasites in ecosystems.