Mitigating the impact of roads on biodiversity requires implementing effective measures to minimize and compensate for impacts. However, ecological mitigation decisions are often constrained by the availability of finances and the feasibility of action. Whilst our research has revealed there are large gaps and biases in the available information on the effectiveness of actions, there are an increasing number of resources available to access relevant information. Available cost information can however be very limited, missing important costs and not provide enough detail to understand it’s relevance to different mitigation contexts. I will start by outlining some of the complexities of cost reporting for road mitigation decisions, discuss potential barriers to providing cost data, and potential solutions that could improve the status quo. Appropriate collation of costs and benefits can reveal important trade-offs, and improve the apparent cost-effectiveness of some mitigation measures. Whilst cost-effectiveness is a vital component of decision making, designing mitigation requires complex trade-offs on effectiveness for specific biodiversity mitigation targets, financial costs and benefits, effects on other environmental and social priorities, as well as the feasibility and acceptability of action to local stakeholders. Tools are available to help combine information, for robust transparent decision making. Failures to test or use the available literature evidence wastes money and effort and also undermines confidence in mitigation and expert knowledge. Continuous progress and innovation are important in mitigation designs but they should be carefully tested and monitored before large-scale adoption in practice.
