Herbivore size matters for productivity‐richness relationships in African savannas: Commentary on Burkepile et al . (2017)

Since the Late Pleistocene, human impact has increasingly resulted in defaunation, or human-caused animal loss, leading to largely impoverished vertebrate communities (Dirzo et al. 2014; McCauley et al. 2015). These extinctions are not random, but are strongly size-selective with large animals going first. This trend is continuing, with native large herbivores being currently increasingly threatened around the globe (Ripple et al. 2015). As a consequence, native herbivore communities both lose their largest members, hence, decreasing in average size, but simultaneously decrease in diversity. This may have strong consequences for the herbivore’s impact on biodiversity, ecosystem functioning and landscape structure (Dirzo et al. 2014; Bakker et al. 2016a). However, field tests of the effect of size-selective loss of vertebrate herbivores remain rare. Burkepile et al. (2017) performed such a test and address the question how the loss of vertebrate herbivores affects plant species richness in African savanna. They incorporated the size-selectivity of herbivore extinctions in their design by using size-selective exclosures to separate the effect of losing only the larger herbivores as elephant, zebra and wildebeest from that of losing all vertebrate herbivores >1 kg together. They subsequently replicated this design across a 10-fold gradient in plant production within Kruger National Park, South Africa.