How does biodiversity affect disease prevalence? To paraphrase a prominent scholar on the subject, there are many more plausible predictions than there are definitive answers. In this talk, I summarize these plausible predictions and ask how specific predictions may be altered by climate-mediated changes in species interactions. I also give voice to the concern that climate change introduces a degree of dynamism that cannot be accounted for in traditional modeling approaches. The prevalence of a particular disease is the outcome of a complex system of interacting species, including but not limited to the host(s), parasite(s) and possibly vector(s) most associated with the disease. This complexity allows for alternate mechanisms through which biodiversity can amplify or dilute factors affecting disease prevalence. It also increases the potential for unforeseen consequences of change in the ecosystems in which disease systems are embedded.
Climate change is altering the biotic and abiotic context of species interactions, in part through rapid changes in species distribution and abundance. These rapid changes threaten our understanding of disease systems in a fundamental way. Specifically, the internal and external forces driving disease dynamics are likely to be in unprecedented flux as we study them. This fact is important to consider as we design studies and modeling efforts. Most theories to date are predicated on the assumption of stasis in the set of factors controlling dynamics. In this time of change, there is an increasing role for the study of complex systems in which the underlying relationships are not invariant in time.