Rewilding – the practice of reintroducing wild flora and fauna into their natural habitats – is a conservation strategy gaining traction worldwide. Carlos Navarro and colleagues have examined rewilding on the Argentine Puna, a high-altitude grassland ecosystem. They wanted to know, how does rewilding, specifically the replacement of domestic herbivores with their wild counterparts, affect biodiversity, particularly in plants and macroinvertebrates?
Historically, the Argentine Puna was home to llamas, vicuñas, and guanacos – South American camelids that grazed these lands for millennia. However, in the past few centuries, European settlers introduced sheep and cattle, displacing the native herbivores. Now, conservation efforts are reversing this trend, reintroducing native camelids and removing domestic livestock. Navarro and colleagues examined the peatlands of the Argentine Andes, to see if the return of wild herbivores is healing the Puna.
The answer is complex.
Paradoxically, peatlands dominated by domestic herbivores, such as cattle and sheep, appear to have higher diversity of wild herbivores, and richer plant and aquatic macroinvertebrate communities. It seems counterintuitive, but it underscores a crucial distinction: high biodiversity does not necessarily mean a healthier ecosystem. It’s the balance of species that counts.
The reason for the difference in biodiversity lies in the grazing patterns. Domestic livestock graze uniformly, eating a bit of everything. In contrast, wild camelids are selective feeders, choosing specific plants and leaving others untouched. This selective grazing can limit plant diversity by promoting certain species at the expense of others. In this way, rewilding doesn’t necessarily decrease grazing pressure; instead, it changes the type and diversity of herbivores. This shift in herbivore community structure can have far-reaching consequences for biodiversity.
Interestingly, bird diversity didn’t show a significant association with the herbivory/wilderness gradient in the study. This lack of correlation raises more questions about the multi-layered connections between different components of the ecosystem. Could mammalian predators, for instance, play a more influential role in determining bird diversity? Future research is needed to delve into these complex interrelations.
The Argentine Puna’s rewilding presents a mixed bag for biodiversity. While it fosters a higher diversity of wild herbivores, it doesn’t necessarily lead to a healthier ecosystem. Importantly, the replacement of domestic herbivores with wild ones doesn’t alleviate grazing pressure but alters it. In their article Navarro and colleagues state:
Andean peatlands are socio-ecological systems that have been managed for centuries to maintain basic hydrological functioning and, after European colonization, human land use involved the increase in herbivore diversity compared to natural ecosystems. This historical pattern of land use is compatible with a comparatively high diversity of plants and aquatic macroinvertebrates, and showed no significant effect on birds. These results contradict the generalization that rewilding necessarily results in biodiversity gains, and emphasize the importance of including human land management as a relevant contributor to biodiversity conservation in high elevation ecosystems.Navarro et al. 2023
This suggests that rewilding is not a one-size-fits-all solution for biodiversity conservation. It’s a complex process that requires a deep understanding of the interplay between different species and the specific historical and ecological context. As the Argentine Puna’s example shows, embracing this complexity is key to the success of future rewilding projects.
READ THE ARTICLE
Navarro, C.J., Carilla, J., Acosta, O.O., Nieto, C., Ovejero, R. and Grau, H.R. (2023) “Herbivore rewilding does not promote biodiversity in Argentine Andean peatlands,” Anthropocene, 42(100382), p. 100382. Available at: https://doi.org/10.1016/j.ancene.2023.100382.