Recognizing and mitigating key uncertainties about the future in ecological restoration planning

Introduction Ecological restoration is about futures that no one has seen. This introduces fundamental uncertainties to the planning process, even in the case when historical or existing reference states of the ecosystems are well documented. Objectives I explain how uncertainties and ignorance could be incorporated into deciding about restoration interventions. Methods Literature synthesis of the main uncertainties documented in restoration and risks of their misjudgment. The risks and their mitigation options are framed according to three basic ethical principles: avoiding environmental harm, understanding natural dynamics, and avoiding moral pollution. Results I describe three classes of socio‐ecological uncertainties related to: (1) alternative post‐restoration ecosystem trajectories; (2) partial recoveries in a foreseeable future; (3) up‐ and downscaling of knowledge. These are complemented by three classes of socio‐cultural uncertainties: (4) alternative human–environment relationships to facilitate; (5) uncertainties of future governance; (6) socio‐cultural spillover effects of restoration. Conclusions Restoration projects could gain from a more complete and explicit assessment of key uncertainties, but also from setting norms and procedures for reducing undesirable outcomes that are due to our inevitably limited knowledge. The potential benefits include allocating restoration efforts more effectively, maintaining credibility of the “precautionary approach” in environmentalism, and avoiding suppression of alternative ecological futures.