Biodiversity conservation is currently facing extraordinary challenges but remains severely limited by funding. Thus, the importance of cost-effective conservation is being increasingly realised – requiring information on both the effects and costs of actions taken to conserve biodiversity. Yet, despite progress in collating and using evidence on the effectiveness of conservation in decision-making, the recording and use of cost data has received far less attention.

This PhD aims to help bridge this gap by investigating the collection and use of economic data for conservation decision making, as part of wider research into evidence-based conservation. The research presented is structured into several stages: i) investigate the current state of cost reporting and the use of evidence (including costs) in conservation decision making, ii) develop frameworks and approaches to help improve the reporting of the economic costs and benefits of conservation actions, and the use of evidence in decision-making around biodiversity impact mitigation. Lastly, I then apply this thinking to two detailed case studies where I assess the costs and cost-effectiveness of different conservation interventions.

Reviewing the published literature on conservation interventions, I identified low rates of detailed cost reporting. Reported costs often lacked important contextual detail necessary to interpret the data and apply it in different contexts. Where detailed costs were provided, they showed considerable variation, with differences in how costs were reported likely to explain much of this variance. I then conducted an interview-based study investigating the use of evidence in business-biodiversity decision making. This revealed a wide range of themes including the high reliance of professionals on experts, policy and guidance as a stamp of cost-effective, evidence-based practice. Several challenges to integrating biodiversity in the private sector were also noted, including the need for better understanding the economic costs and benefits of mitigation action.

Building on these studies, I then developed i) a step-by-step framework for the standardised reporting of economic costs and benefits of conservation action, and ii) a set of principles for the use of evidence (including data on costs) to guide actions that businesses and consultants can take to minimize and compensate for their impacts on biodiversity.

To demonstrate the complexities and importance of using cost data in decision-making, I then provide two case studies. The first of these studies assesses the costs and cost-effectiveness of actions to avoid and minimize the impacts of power lines on at-risk bird species in Spain. The study identified large variations in the effectiveness and cost-effectiveness of different actions to prevent collisions with at-risk bird species. Changing how cost is measured, by including the costs associated with negative impacts, can improve the apparent cost-effectiveness of mitigation measures, particularly those more effective measures which avoid impact at the outset.

In the second case study, I used a dataset of field-level costs of commonly applied agri-environment interventions in the UK to investigate actions to protect and restore biodiversity in farmland. I identified a high variation in costs both between and within different conservation actions. Costs and cost-effectiveness varied depending on the inclusion of several inputs (e.g., fertilizer, pesticide) during implementation, field size, as well as the types of cost and benefit included. Understanding the variability in costs within actions, and how costs and cost-effectiveness are calculated, are critical considerations when assessing the feasibility of different actions to protect and restore biodiversity.