Herbivore rewilding does not promote biodiversity in Argentine Andean peatlands

Abstract

The Argentine Puna is an example of rewilding of the herbivore community, with wild camelids recovering (mainly vicuñas, Vicugna vicugna and guanacos Lama guanicoe) while livestock decreases. Peatlands are the most diverse ecosystem in the region and are key resources for herbivores. Here, we tested the hypothesis that herbivore rewilding is associated with higher biodiversity of three biological groups: plants, aquatic macroinvertebrates, and birds. We sampled 50 peatlands distributed in the Argentine Puna, along an elevation range from 3200 to 4700 m asl. Using Non-metric multidimensional scaling (NMDS), we developed a “wilderness index” that combines different proxies of pastoral use (herbivore feces, “puestos”, accessibility to human settlements, field counts of herbivores). In general, the diversity of the different groups was negatively correlated with elevation and positively correlated with peatland area, thus we used the residuals of a model to control for these two variables and test for the correlation between biodiversity patterns (Shannon index and richness) and peatland wilderness index. Contrary to our expectations, diversity of plant and macroinvertebrate communities’ showed slightly negative statistically significant correlations with wilderness, while birds showed no statistical association. Potential explanations for this pattern include (1) diversity of microhabitats generated by a more diverse herbivore's community associated with livestock (e.g., different trampling, browsing, and movement patterns, effects on water quality through feces), (2) management of hydrological regimes and stocking rates to provide stability, (3) herbivory dynamics that promote the dominance of certain plants. Overall, the results reject the hypothesis that herbivore rewilding automatically results in biodiversity gains, and emphasize the importance of understanding the socio-ecological mechanisms by which human land use (including exotic livestock) contributes to the biodiversity maintenance in these key ecosystems.