Idea and Perspective
Understanding patterns and processes in models of trophic cascades
Article first published online: 27 OCT 2013
© 2013 The Authors. Ecology Letters published by John Wiley & Sons Ltd and CNRS.
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
Volume 17, Issue 1, pages 101–114, January 2014
How to Cite
Ecology Letters (2013) 17: 101–114
- Issue published online: 16 DEC 2013
- Article first published online: 27 OCT 2013
- Manuscript Accepted: 19 SEP 2013
- Manuscript Revised: 10 SEP 2013
- Manuscript Revised: 25 JUL 2013
- Manuscript Revised: 19 JUN 2013
- Manuscript Received: 10 MAY 2013
- Marine Alliance for Science and Technology for Scotland. Grant Number: HR09011
- National Science Foundation. Grant Number: OCE-1258667
- density dependence;
- food chain;
- food web;
Climate fluctuations and human exploitation are causing global changes in nutrient enrichment of terrestrial and aquatic ecosystems and declining abundances of apex predators. The resulting trophic cascades have had profound effects on food webs, leading to significant economic and societal consequences. However, the strength of cascades–that is the extent to which a disturbance is diminished as it propagates through a food web–varies widely between ecosystems, and there is no formal theory as to why this should be so. Some food chain models reproduce cascade effects seen in nature, but to what extent is this dependent on their formulation? We show that inclusion of processes represented mathematically as density-dependent regulation of either consumer uptake or mortality rates is necessary for the generation of realistic ‘top-down’ cascades in simple food chain models. Realistically modelled ‘bottom-up’ cascades, caused by changing nutrient input, are also dependent on the inclusion of density dependence, but especially on mortality regulation as a caricature of, e.g. disease and parasite dynamics or intraguild predation. We show that our conclusions, based on simple food chains, transfer to a more complex marine food web model in which cascades are induced by varying river nutrient inputs or fish harvesting rates.