Assessing costs and cost-effectiveness across the mitigation hierarchy: An example considering the reduction of bird mortality at power lines

There is an increasing expectation for companies to revise their activities to minimize impacts on biodiversity, as well as undertake compensatory and proactive actions to restore biodiversity. To contribute towards global biodiversity goals, such actions need to be both ambitious and effective. Yet, implementation of mitigation actions to avoid impact is often poor or omitted, and actions to minimize and restore can be of varying effectiveness. The financial costs of actions are often seen as a barrier. Here we argue that mitigation costs, both costs incurred or avoided, are often overlooked or over-simplified when designing mitigation strategies. This includes limited quantification of management costs, the costs of potential impacts, assumed counterfactuals (i.e., what would happen without mitigation?), the distribution of costs between stakeholders, and the value gained by enhancing biodiversity. A more detailed and nuanced understanding of the economic costs and benefits of mitigation actions can both help prioritize resources more efficiently and reveal the true cost-effectiveness of mitigation at the project and portfolio levels, particularly for actions that avoid damage to biodiversity. This could improve the implementation of the mitigation hierarchy, as project developers or decision makers have a better understanding of the actual costs and benefits of different potential mitigation strategies. We exemplify this thinking with a detailed case study that determines the costs and effectiveness of a range of actions to reduce bird collisions on power lines.