Combining paleo-data and modern exclosure experiments to assess the impact of megafauna extinctions on woody vegetation.
Until recently in Earth history, very large herbivores (mammoths, ground sloths, diprotodons, and many others) occurred in most of the World's terrestrial ecosystems, but the majority have gone extinct as part of the late-Quaternary extinctions. How has this large-scale removal of large herbivores affected landscape structure and ecosystem functioning? In this review, we combine paleo-data with information from modern exclosure experiments to assess the impact of large herbivores (and their disappearance) on woody species, landscape structure, and ecosystem functions. In modern landscapes characterized by intense herbivory, woody plants can persist by defending themselves or by association with defended species, can persist by growing in places that are physically inaccessible to herbivores, or can persist where high predator activity limits foraging by herbivores. At the landscape scale, different herbivore densities and assemblages may result in dynamic gradients in woody cover. The late-Quaternary extinctions were natural experiments in large-herbivore removal; the paleoecological record shows evidence of widespread changes in community composition and ecosystem structure and function, consistent with modern exclosure experiments. We propose a conceptual framework that describes the impact of large herbivores on woody plant abundance mediated by herbivore diversity and density, predicting that herbivore suppression of woody plants is strongest where herbivore diversity is high. We conclude that the decline of large herbivores induces major alterations in landscape structure and ecosystem functions.
Department of Aquatic Ecology, Netherlands Institute of Ecology, 6708 PB Wageningen, The Netherlands; l.bakker@nioo.knaw.nl.
Elisabeth S
ES
Bakker
School of Biology and Ecology, Climate Change Institute, University of Maine, Orono, ME 04469;
Jacquelyn L
JL
Gill
School of Biological Sciences, University of Tasmania, Hobart, TAS 7001, Australia;
Christopher N
CN
Johnson
Community and Conservation Ecology, Institute for Evolutionary Life Sciences, University of Groningen, 9700 CC Groningen, The Netherlands;
Frans W M
FW
Vera
The Recanati-Kaplan Centre, Wildlife Conservation Research Unit, Department of Zoology, Oxford University, Tubney OX13 5QL, United Kingdom;
Christopher J
CJ
Sandom
Department of Global Ecology, Carnegie Institution for Science, Stanford, CA 94305;
Gregory P
GP
Asner
Section for Ecoinformatics & Biodiversity, Department of Bioscience, Aarhus University, DK-8000 Aarhus C, Denmark.
Jens-Christian
JC
Svenning
D063147:Animal Distribution; D000818:Animals; D001522:Behavior, Animal; D044822:Biodiversity; D049628:Body Size; D057486:Carbon Cycle; D017753:Ecosystem; D004606:Elephants / Q000502:physiology; D053476:Extinction, Biological; D005544:Forecasting; D065928:Forests; D060434:Herbivory; D049690:History, Ancient; D008322:Mammals; D056666:Mastodons / Q000502:physiology; D008954:Models, Biological; D010163:Paleontology; D063148:Plant Dispersal; D011235:Predatory Behavior; D014197:Trees
browsers; ecosystem functions; herbivore diversity; landscape structure; megaherbivore