When to Restore: Human-assisted (active) restoration is often but not always more cost-effective than monitored natural recovery (passive restoration); thus, it is wise to evaluate whether active restoration is necessary. Pursuing restoration as early as possible will help prevent ecosystems from transitioning to undesired alternative stable states, and including ecological economists early in restoration will help identify the most cost-effective approach to restoration.

What to Restore: The process of developing a restoration plan with involvement of stakeholders should determine whether the restoration goal should be remediation, restoration to historical conditions, or restoration to a hybrid or novel ecosystem. Subsequently, the plan should entail establishing measurable goals and benchmarks within a realistic range of values; selecting a combination of structural, compositional, and functional restoration endpoints; and identifying multiple reference sites that reflect the range of natural variation. If the goal is a hybrid or novel ecosystem, then ideally this ecosystem should be designed to deliver more services and be more resistance and resilient than the historical ecosystem.

Where to Restore: On-site restoration is often more desirable than off-site restoration, but off-site restoration might be necessary where compensatory restoration is required or where conditions cannot be improved in the long-term to support the targeted biodiversity and functions. Two of the biggest challenges to restoration science will be to develop restoration approaches that can address the impediment of rural poverty in the developing world, and to identify and then balance the ecosystems and regions in most need of restoration and those that are best positioned for restoration success.

How to Restore - Economics: Market-based strategies have been developed to meet the challenge of funding restoration, such as environmental insurance bonds and Payment for Ecosystem Services frameworks where ecosystem service credits can be bought and sold. Payment for Ecosystem Services systems are promising because they incentivize restoration and can produce considerable administrative cost savings, and credits can be combined to pursue larger scale restoration that can facilitate the return of apex predators.

How to Restore - Ecology: Because ecosystem engineers reduce the threshold of human effort needed to attain desired states and they often represent self-sustaining solutions, ecosystem engineers might be inexpensive, easy, fast, sustainable, and in some cases, the only feasible restoration option. Restoration success could be improved by employing proven methods for animal and plant reintroductions; more thoroughly considering site history, landscape and aquascape perspectives, species coexistence and community assembly theories; and employing a more inclusive toolbox that holistically considers alterations to propagule pressure, abiotic conditions, and biotic interactions. A more inclusive toolbox could also improve the cost-effectiveness of restoration.

Assessing Restoration Success: Monitoring restoration endpoints and reference conditions are essential to evaluating restoration progress and success. Of the restoration projects with adequate monitoring, the most successful ones have employed adaptive management; have had significant community and stakeholder involvement, an advisory committee, collaborations among scientists, managers, and practitioners; and have had formal evaluation throughout the restoration process. Overly precise restoration prescriptions enacted at broad policy or regulatory scales can often reduce success by homogenizing restored areas, thus reducing the resilience of ecosystems to environmental change. Future assessments of success should consider measuring links between composition and ecosystem functions and incorporating metagenomic and metatranscriptomic approaches for a more complete assessment of biodiversity and functions.

Conclusion: E. O. Wilson suggested that ecological restoration “is the means to end the great extinction spasm” and that “the next century will…be the era of restoration in ecology” (Wilson 1999), emphasizing the future value and prominence of restoration ecology. We hope that this overview of many of the key ecological and economic concepts in restoration ecology will help clarify the discipline. Most importantly, we are optimistic that the recommendations provided here will facilitate restoring and maintaining the services and products provided by natural capital, and thus improve human livelihoods and hope for the future of humanity.