Ecological Context of Lyme Disease
Biodiversity, Habitat Fragmentation,
and Risk of Infection
Richard S. Ostfeld
Eric M. Schauber
Kenneth A. Schmidt
Rapid, human-induced erosion of biological diversity may have enormous consequences for the transmission of infectious diseases to humans. The consequences of biodiversity loss for human health are only beginning to be understood. The development of theory linking biodiversity to risk of infectious diseases has been slow, and empirical studies based on a solid theoretical foundation are few. How might biodiversity loss influence the probability of human exposure to infectious diseases? At one extreme, imagine that all the natural habitats surrounding a town are converted into parking lots, resulting in a massive loss of local biodiversity. Such a change might be expected to wipe out many diseases simply because the pathogens and their reservoirs and vectors would cease to exist. In such a case, biodiversity loss would reduce disease risk. However, another scenario might entail the conversion of diverse natural vegetation to much less diverse agricultural fields, optimizing the habitat for outbreaks of commensal mice and leading to epidemics of diseases for which the mice are reservoirs (e.g., Mills and Childs 1998; Keesing 2000). Loss of biodiversity in this landscape would increase disease risk. Whether the loss of biodiversity decreases or increases disease risk is thus likely to depend on which species are lost or reduced, the spatial patterns and magnitude of diversity loss, and the consequences of diversity loss for the dynamics of the remaining species, including the pathogens and parasites. Progress in understanding and predicting the consequences of eroding biodiversity for human health will require the development of a strong theoretical foundation combined with rigorous empirical studies.
In this chapter, we focus on linkages between community ecology and risk of human exposure to zoonotic diseases. Zoonotic diseases are those in which a pathogen normally resides in one or more species of animal hosts but may be