• DOI:10.1073/pnas.1915769117
• Corpus ID: 214627869

Introduced herbivores restore Late Pleistocene ecological functions

@article{Lundgren2020IntroducedHR,
  title={Introduced herbivores restore Late Pleistocene ecological functions},
  author={Erick J. Lundgren and Daniel Ramp and John Rowan and Owen S Middleton and Simon D. Schowanek and {\'O}scar Sanisidro and Scott P Carroll and Matt Davis and Christopher J. Sandom and Jens‐Christian Svenning and Arian D. Wallach},
  journal={Proceedings of the National Academy of Sciences},
  year={2020},
  volume={117},
  pages={7871 - 7878}
}

• Erick J. Lundgren, D. Ramp, +8 authors Arian D. Wallach
• Published 23 March 2020
• Environmental Science, Geography
• Proceedings of the National Academy of Sciences

Significance Humans have caused extinctions of large-bodied mammalian herbivores over the past ∼100,000 y, leading to cascading changes in ecosystems. Conversely, introductions of herbivores have, in part, numerically compensated for extinction losses. However, the net outcome of the twin anthropogenic forces of extinction and introduction on herbivore assemblages has remained unknown. We found that a primary outcome of introductions has been the reintroduction of key ecological functions, making herbivore assemblages with nonnative species more similar to preextinction ones than native-only assemblages are. Our findings support calls for renewed research on introduced herbivore ecologies in light of paleoecological change and suggest that shifting focus from eradication to landscape and predator protection may have broader biodiversity benefits. Large-bodied mammalian herbivores dominated Earth’s terrestrial ecosystems for several million years before undergoing substantial extinctions and declines during the Late Pleistocene (LP) due to prehistoric human impacts. The decline of large herbivores led to widespread ecological changes due to the loss of their ecological functions, as driven by their unique combinations of traits. However, recently, humans have significantly increased herbivore species richness through introductions in many parts of the world, potentially counteracting LP losses. Here, we assessed the extent to which introduced herbivore species restore lost—or contribute novel—functions relative to preextinction LP assemblages. We constructed multidimensional trait spaces using a trait database for all extant and extinct mammalian herbivores ≥10 kg known from the earliest LP (∼130,000 ybp) to the present day. Extinction-driven contractions of LP trait space have been offset through introductions by ∼39% globally. Analysis of trait space overlap reveals that assemblages with introduced species are overall more similar to those of the LP than native-only assemblages. This is because 64% of introduced species are more similar to extinct rather than extant species within their respective continents. Many introduced herbivores restore trait combinations that have the capacity to influence ecosystem processes, such as wildfire and shrub expansion in drylands. Although introduced species have long been a source of contention, our findings indicate that they may, in part, restore ecological functions reflective of the past several million years before widespread human-driven extinctions.