Cause vs. correlation in disease ecology: Biodiversity as both a driver and a response to global change
Habitat destruction and climate change have altered communities of organisms and globalization of trade and travel have introduced pathogens to new regions. In the last decade there has been substantial interest in the effect of changes in biodiversity in the host community on the transmission of pathogens or what has been termed the dilution effect. Despite a substantial number of studies examining correlations between biodiversity and disease risk, there is strong disagreement about what the data indicate. While there have been several theoretical papers examining the conditions needed for a dilution effect, much less attention has been given to the difficulties and potential for false attribution in interpreting data from observational studies.
I examine data from published studies and show that the very environmental variation that generates differences in host communities is likely to directly result in differences in transmission, which are often falsely attributed to variation in host diversity. I outline a research approach to determine the influence of host community composition on pathogen transmission that avoids these issues by combining observational data and either models or experiments. Determining the impact of species diversity on disease risk can improve public health and contribute to conservation.