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Author Notes:

Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, NY 10027, USA email:christina.faust@glasgow.ac.uk

L.S.P.B., A.P.D., C.L.F., T.R.G., N.G., H.I.M. and R.K.P. conceived the study. C.L.F., A.P.D., R.K.P. and N.G. designed the study and analysed the results.

C.L.F., N.G., L.S.P.B. and T.R.G. acquired empirical data for model conceptualization.

C.L.F., R.K.P., N.G., A.P.D., L.S.P.B., M.D.-W., H.I.M. and T.R.G. wrote the manuscript and all contributed to the editing and approval of the final draft.

We are grateful to the editor and two anonymous reviewers for their thoughtful comments that helped to significantly improve the manuscript.

We would like to thank other members of the SESYNC/NCEAS Land Use Change and Infectious Diseases Working Group who gave feedback and provided stimulating discussions throughout the workshop series.

In particular, we would like to acknowledge A. Baeza Castro, N. Bharti, M. Bonds, G. De Leo, M. Levy, C. Ngonghala, M. Pascual and M. Santos Vega.

We have no competing interests.


Research Funding:

This work was supported by the National Socio-Environmental Synthesis Center (SESYNC) and the National Center for Ecological Analysis and Synthesis (NCEAS) under funding received from the National Science Foundation DBI-1052875 and DEB-94–21535, respectively.

C.L.F. was funded by the National Defence Science and Engineering Graduate Fellowship and the Truman Foundation.

M.D.-W. was supported by the National Institutes of Health, Ecology and Evolution of Infectious Disease Program (5R01GM105246).

R.K.P. was supported by National Institutes of Health IDeA Program grants P20GM103474 and P30GM110732, P. Thye and Montana University System Research Initiative: 51040-MUSRI2015-03.


  • allometry
  • amplification effect
  • dilution effect
  • disease ecology
  • habitat loss
  • infectious disease dynamics
  • multi-host
  • Animals
  • Biodiversity
  • Communicable Diseases
  • Ecosystem
  • Humans

Null expectations for disease dynamics in shrinking habitat: Dilution or amplification?


Journal Title:

Philosophical Transactions B: Biological Sciences


Volume 372, Number 1722


, Pages 20160173-20160173

Type of Work:

Article | Final Publisher PDF


As biodiversity declines with anthropogenic land-use change, it is increasingly important to understand how changing biodiversity affects infectious disease risk. The dilution effect hypothesis, which points to decreases in biodiversity as critical to an increase in infection risk, has received considerable attention due to the allure of a win–win scenario for conservation and human well-being. Yet some empirical data suggest that the dilution effect is not a generalizable phenomenon.We explore the response of pathogen transmission dynamics to changes in biodiversity that are driven by habitat loss using an allometrically scaled multi-host model.With this model, we show that declining habitat, and thus declining biodiversity, can lead to either increasing or decreasing infectious-disease risk, measured as endemic prevalence. Whether larger habitats, and thus greater biodiversity, lead to a decrease (dilution effect) or increase (amplification effect) in infection prevalence depends upon the pathogen transmission mode and how host competence scales with body size. Dilution effects were detected for most frequency-transmitted pathogens and amplification effects were detected for density-dependent pathogens. Amplification effects were also observed over a particular range of habitat loss in frequency-dependent pathogens when we assumed that host competence was greatest in large-bodied species. By contrast, only amplification effects were observed for density-dependent pathogens; host competency only affected the magnitude of the effect. These models can be used to guide future empirical studies of biodiversity–disease relationships across gradients of habitat loss. The type of transmission, the relationship between host competence and community assembly, the identity of hosts contributing to transmission, and how transmission scales with area are essential factors to consider when elucidating the mechanisms driving disease risk in shrinking habitat.

Copyright information:

© 2017 The Author(s) Published by the Royal Society. All rights reserved.

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