Opportunities, research gaps, and risks in allogenic ecosystem engineer mimicry.

In an age of anthropogenically driven species loss and increasingly novel ecosystems, ecosystem engineer restoration is a process-based approach to supporting ecosystem function. Many ecosystem engineers have low or declining population sizes. When feasibility and costs impede reintroduction of ecosystem engineers, an alternative may be artificial mimicry of ecosystem engineer structures. Research on mimicry of autogenetic ecosystem engineers, whose physical structure shapes habitat availability and complexity (e.g., tropical corals whose hard skeletons create complex reefs that provide habitat), spans many process scales. However, mimicry of allogenic ecosystem engineers, which shape habitat availability through their behavior (e.g., beavers building dams that influence hydrology), is less well explored. We reviewed the literature to examine the efficacy of artificial mimicry of allogenic ecosystem engineers and gaps in the research. Emerging findings suggest that artificial mimicry could restore physical processes, support focal species, alter biological communities, deliver benefits to landowners and ecosystems, and promote population recovery. However, some studies document the potential for unintended negative consequences for ecosystem engineers or species that use engineered structures or respond to environmental cues produced by engineered structures. Topics requiring additional research include assessing the efficacy of artificial structures as compared with natural structures, evaluating the scalability and cost-effectiveness of mimicry projects, and investigating the potential for unintended consequences with mimicked structures.