Roads and wildlife: the need for evidence-based decisions; New Zealand bats as a case study

Roads and associated land transport activities can affect a wide range of indigenous terrestrial vertebrate species. National legislation, particularly the Resource Management Act 1991, requires that developers ‘avoid, remedy or mitigate’ the adverse environmental effects of their activities. How these effects are identified and managed in New Zealand varies because regulators and land transport contractors deal with these issues on a case-by-case basis. In recent years, the effects of new road projects on long-tailed bats (Chalinolobus tuberculatus) have been receiving attention. In this review, we summarise evidence on likely road infrastructure impacts on bat populations and the efficacy of mitigation approaches, used both internationally and in New Zealand. Our findings indicate that most mitigation methods have little, if any, scientific evidence of their effectiveness. We recommend that such evidence is essential to guide investment in mitigating road effects on bats in New Zealand. Given that such evidence is rare, future investment should be guided by an adaptive management framework that is justified by strong, inferential, evidence-based logic, and accompanied by robust, appropriately designed monitoring planned, in advance, to allow an objective assessment of a method’s effectiveness in mitigating an impact. Because such monitoring may be beyond what a single development project can realistically achieve, we suggest the development of a collaborative funding model for supporting the testing and development of mitigation methods. This work is likely to have a significant influence on the future planning and design of road infrastructure projects to minimise the impacts on bats and, more generally, on any native wildlife populations under threat from infrastructure development.