Considering intervention intensity in habitat restoration planning: An application to Pacific salmon

Habitat restoration is a key strategy for recovering imperiled species, and planning habitat restoration activities cost effectively can help advance recovery objectives. Habitat restoration planning involves decisions about where and when to undertake restoration, and what type of restoration to undertake. This article focuses on decisions about the amount of restoration to undertake for a given type, location, and time, termed intervention intensity. A return on investment framework is developed for incorporating intervention intensity into habitat restoration planning. The framework is then applied in the context of planning habitat restoration for Pacific salmon recovery as a case study. Results showed that no single intervention type or location dominated, and several returns to scale relationships emerged across the candidate interventions. Scenarios that considered interventions across multiple intensities outperformed single-intensity scenarios in terms of total benefits and cost effectiveness. These findings highlight the usefulness of exploratory return on investment analysis for prioritizing habitat restoration interventions, and underscore the importance of systematically considering how much restoration to undertake, in addition to what to do and where.