The Editor’s Choice for issue 55:2 is written by Associate Editor, Jörg Müller. The selected article is Livestock activity increases exotic plant richness, but wildlife increases native richness, with stronger effects under low productivity by David J. Eldridge et al.
Browsing and grazing by wild ungulates and livestock affect the vegetation layer in complex ways, creating many management conflicts in silviculture, restoration and conservation. However, certain types of herbivory can have positive as well as negative effects on plant diversity or ecosystem functions.
We live in a world full of altered herbivore communities: while some native species are extinct in many places, others have increased by anthropogenic promotion – the introduction of only sometimes functionally similar livestock – elsewhere. All of this can be seen in plant communities consisting of both native and exotic species. Such complexity hampers general implications about ecological consequences of herbivory, but is required by managers (Putman 1986; Bernes et al. 2015).
Today, Australia is characterized by a strong variation in local densities of non-native herbivores, such as feral goats and rabbits, as well as native species, such as kangaroos. Both have been identified as challenging for ecosystems. In their recent study, Eldridge et al collected data on climate, plant productivity, grazing intensity and herbivore type at 451 sites within an impressively large area in eastern Australia. Taking into account this study design, livestock and wild herbivores, along a climate and productivity gradient, opened the avenue to disentangle direct and indirect effects on native and exotic plant species via structural equation modelling. The strongest effect of herbivory was found under low productivity. Overall the study shows that livestock increases exotic plant species richness and reduces native plant richness. In contrast, grazing by the native kangaroos increases plant species richness in environments with low productivity. These findings provide a strong message for managers and decision makers: the coexistence of livestock and native plant species is not critical from a conservation perspective, only in more productive environments.
The results demonstrate the power of large-scale survey data, collected along large environmental gradients, together with structural equation models, to identify direct and indirect effects of herbivores on plant communities. The intricacies of the complex relation of herbivore type, productivity and plant species richness underline the importance of context-dependent management decisions about livestock grazing with respect to conservation of biodiversity. An improved understanding of the multiple interactions of environmental gradients and biotic interactions in a climatically changing world area is of particular importance in guiding managers and policy makers. Moreover the study might stimulate similar research in other parts of the world with different environmental gradients and mixtures of native and exotic herbivores.
Read the full article, Livestock activity increases exotic plant richness, but wildlife increases native richness, with stronger effects under low productivity in issue 55:2 of Journal of Applied Ecology.
Find out more about Editor’s Choice articles here.