Introduction

Ecosystem restoration is one of the most promising strategies to mitigate biodiversity loss. Plant-animal interactions are critical to biodiversity maintenance and ecosystem functioning and consequently are essential to the success of restoration strategies. However, systematic assessments of how restoration efforts consider such interactions are lacking.

Objectives / Hypothesis

We synthesized available knowledge on restoration of plant-animal interactions by focusing on four specific questions: (1) to what extent are interactions recovered in restored sites compared to degraded and reference sites? (2) which management practices enhance interaction restoration? (3) which interactions and animal taxa are most frequently studied? (4) is interaction restoration being studied in areas deemed critical for conservation?

Methods

We reviewed 127 articles that studied plant-animal interactions in habitat restoration and trophic rewilding. These articles focused on either of four key plant-animal interactions: seed dispersal, herbivory, pollination, and seed predation. To assess whether these interactions have been restored, we conducted a meta-analysis using a subset of 56 studies that compared restored systems vs. degraded or undisturbed (i.e., reference) systems.

Results

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. Seed dispersal and pollination were recovered in restored sites as compared to degraded sites, but not in comparison to reference sites. While several studies were conducted in critical conservation sites, some biodiversity hotspots, particularly in Southeast Asia, have been understudied.

Conclusions

Habitat restoration and trophic rewilding seem to be effective in bringing seed dispersal and pollination to a better state than in degraded areas. The evidence for herbivory and seed predation is inconclusive. Interaction restoration research and implementation represent critical, pending agendas, particularly in some tropical regions.