A simple model predicts how warming simplifies wild food webs

Abstract

Warming increases the metabolic demand of consumers1, strengthening their feeding interactions2. This could alter energy fluxes3,4,5 and even amplify extinction rates within the food web6,7,8. Such effects could simplify the structure and dynamics of ecological networks9,10, although an empirical test in natural systems has been lacking. Here, we tested this hypothesis by characterizing around 50,000 directly observed feeding interactions across 14 naturally heated stream ecosystems11,12,13,14,15. We found that higher temperature simplified food-web structure and shortened the pathways of energy flux between consumers and resources. A simple allometric diet breadth model10,16 predicted 68–82% of feeding interactions and the effects of warming on key food-web properties. We used model simulations to identify the underlying mechanism as a change in the relative diversity and abundance of consumers and their resources. This model shows how warming can reduce the stability of aquatic ecosystems by eroding the structural integrity of the food web. Given these fundamental drivers, such responses are expected to be manifested more broadly and could be predicted using our modelling framework and knowledge of how warming alters some routinely measured characteristics of organisms.

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Fig. 1: The effect of temperature on the properties of food webs.
Fig. 2: Temperature effects on energy flux.
Fig. 3: Effect of randomizations on temperature dependence of food-web properties.
Fig. 4: Key determinants of food-web properties.

Data availability

The data that support the findings of this study are available from E.J.O. on reasonable request.

Code availability

The R code that supports the findings of this study is available from E.J.O. on reasonable request.

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Acknowledgements

We thank G. M. Gíslason for providing research support and laboratory facilities; R. L. Kordas (Imperial College London, UK), G. Adams (University College London, UK), E. J. Cox and L. M. Cachazo (Natural History Museum, London, UK), I. Hansen and S. O. Helgason (Marine and Freshwater Research Institute, Iceland), and P. C. Furey (St Catherine University, USA) for help with taxonomic identification. We acknowledge funding from NERC (NE/I009280/2, NE/F013124/1, NE/L011840/1 and NE/M020843/1), Imperial College London’s Masters in Ecology, Evolution and Conservation, and the University of Zurich Research Priority Programme Global Change and Biodiversity.

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E.J.O., O.L.P. and G.W. were responsible for funding applications, research design and planning of the experiments. E.J.O., K.J.F., B.G., T.A.C.G., J.N.-C., J.S.Ó., D.E.P. and M.S.A.T. collected the data. E.J.O and O.L.P. analysed the data. All authors wrote the paper.

Corresponding authors

Correspondence to Eoin J. O’Gorman or Guy Woodward.

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Peer review information: Nature Climate Change thanks Micael Jonsson, Oswald Schmitz and other, anonymous, reviewer(s) for their contribution to the peer review of this work.

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Supplementary Methods, Supplementary Figs. 1–16, Supplementary Tables 1–7 and Supplementary References.

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O’Gorman, E.J., Petchey, O.L., Faulkner, K.J. et al. A simple model predicts how warming simplifies wild food webs. Nat. Clim. Chang. 9, 611–616 (2019). https://doi.org/10.1038/s41558-019-0513-x

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