Prehistoric and historic baselines for trophic rewilding in the Neotropics

Abstract

A promising, but also controversial approach to ecological restoration is trophic rewilding, i.e., species introductions to restore top-down trophic interactions and associated trophic cascades to promote self-regulating biodiverse ecosystems. To provide historically-informed base-lines for trophic rewilding in the Neotropics, we aggregate data on late-Quaternary (last 130,000 years) large-bodied (megafauna, here: ≥10kg body mass) mammals to estimate two base-lines: megafaunas including historically (post-1500 AD) extinct species and accounting for regional extirpations of extant species (historic base-line), and megafaunas additionally including Late Pleistocene-Holocene prehistorically extinct species (prehistoric base-line). The historic base-line is less controversial, while the prehistoric base-line is more relevant from an evolutionary, long-term perspective. The estimated potential distributions indicate strong scope for trophic rewilding, with high levels for the prehistoric baseline (with >20 species missing in many regions and biomes), but also considerable values for the historical baseline. Many areas have strongly reduced diversities for a range of functional and phylogenetic subgroups. We discuss implications, highlighting the need for a more nuanced view on non-native megafauna species as they may sometimes represent taxon substitutions for missing species. We emphasize that trophic rewilding should be implemented flexibly and in dialogue with society, e.g., handling human–wildlife conflicts and ensuring benefits for local livelihoods.