Megaherbivores transition along an Andean elevational gradient

Abstract

Historically, herbivory by large native mammals was replaced by domestic livestock. The Andes is not exception: following the European arrival, large herbivores communities (mostly camelids and deer) were largely replaced by sheep, cattle, goats, horses and donkeys. Due to current trends towards human population urbanization and dis-intensification of agricultural marginal areas, this trend could be reversing in different regions, with important ecological consequences. Here, we describe the patterns along the elevational gradient of subtropical mountains of northwest Argentina. In lowland montane forests, tree communities show an expansion of herbivory-sensitive species, likely due to the low herbivores density resulting both from decreasing livestock (cattle) pressure and a slow recovery from past defaunation (e.g. Mazama deer, Tayassu peccaries). In middle elevation tree-grasses ecotones, decreasing sheep density without rapid recovery of native fauna, implies a higher availability of fine fuels and resulting increase in fire frequency. In high elevation Puna desserts, decreasing livestock is being rapidly replaced by expansion of native camelids. These specific change could have consequences for both herbivory and predation; which begins to be reflected in Puma-livestock conflicts. Overall, this diversity of “megaherbivory transitions” resembles the well studied processes of “forest transition” as a mayor land change resulting from socioeconomic modernization, and we discuss the variety of socioecological drivers and consequences.