Effects of mammalian herbivore declines on plant communities

Dr. Hillary Young and colleagues have a paper in the Journal in Early View titled Effects of mammalian herbivore declines on plant communities: observations and experiments in an African savanna. Read the paper here.

The authors have provided a short synopsis of the paper, and some great photos in the field during their study.

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Anthropogenic impact is leading to significant changes in large herbivore populations globally. While we know that changes in the abundance of large herbivores often cause dramatic changes to plant community composition and structure in natural and managed systems, the magnitude and even direction of plant responses to such changes can vary strongly across studies and sites.

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In this paper, we demonstrate that environmental and anthropogenic contexts explain some of this variation in plant community responses to changes in abundance of large wild and domestic herbivores in an African savanna landscape.   We examine this using both experimental manipulations of wild and domestic herbivore densities, and more typical, anthropogenically driven gradients in wild and domestic herbivores across the landscape.  We find that environmental context, particularly mean rainfall, drives much of the variation seen in plant community response to herbivore changes, with stronger responses occurring in lower rainfall environments.  We also find that effects of changes in herbivore abundance on plant communities varied strongly between experimental and landscape contexts, as did the importance of environmental context in modulating plant responses to herbivores. This is at least partially due to the fact that, in practice, wild herbivore decline is often accompanied by large increases in livestock, which can obscure or even overwhelm the effects of changes in wild herbivore abundance.

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Our results underscore the importance of including environmental and anthropogenic contexts in predicting the effects of wild herbivore declines on landscapes.  They also suggest we need to be cautious in using results from experimental manipulations to predict likely consequences of wild herbivore decline as it typically proceeds in Anthropocene landscapes.

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