Restoration of plant-animal interactions in terrestrial ecosystems

Ecosystem restoration is one of the most promising strategies for conservation in the Anthropocene. Within ecosystems, plant-animal interactions are critical to their functioning, biodiversity and to restoration success. However, there is no systematic assessment of such interactions across restoration efforts. We reviewed 127 articles that examined habitat restoration and trophic rewilding to synthesize knowledge on restoration of four key plant-animal interactions: seed dispersal, herbivory, pollination, and seed predation. We conducted a metaanalysis using a subset of 56 studies, which compared restored systems with degraded or reference systems. We addressed four questions: (i) To what extent are interactions recovered in restored sites compared to degraded and reference sites? (ii) Which management practices enhance interaction restoration? (iii) Which interactions and animal taxa were most frequently studied? and (iv) Is interaction restoration being studied in areas deemed critical for conservation? Seed dispersal was the most studied interaction, followed by herbivory, pollination, and seed predation. Mammals were the most studied group, followed by birds, insects, and reptiles. Importantly, occurrence of seed dispersal and pollination was more frequent in restored than degraded sites. While several studies were conducted in critical conservation sites, some biodiversity hotspots, particularly in Southeast Asia, have been understudied. Future research should focus on understudied interactions (e.g., seed predation) and taxa (e.g., insects and reptiles), so this information can be incorporated into practice. Considering the available studies, we find that both habitat restoration and trophic rewilding are effective in bringing seed dispersal and pollination to a better state than in degraded areas.