Associate Editor, Sharif A. Mukul discusses the recent article by Polak et al. Optimal planning to mitigate the impacts of roads on multiple species.

Road development is a continuous process that takes place even in the most remote parts of the world. In recent years the number and extent of the road have expanded dramatically worldwide. Road development can affect biodiversity, particularly wildlife, through habitat loss, habitat fragmentation and direct mortality. Such consequences, however, have rarely been taken into consideration in most road development projects. Using decision theory with a metapopulation model, Polak and colleagues have tried to identify the optimal planning strategy to reduce the effects of road development on wildlife population based on cost-effectiveness of different mitigation strategies.

Wildlife corridor fencing
Building wildlife corridor with fencing could facilitate wildlife movement in areas with high diversity value.
Photo: Tropical North Queensland, Australia by Sharif A. Mukul

In their study, the authors have considered a hypothetical landscape with three mitigation options:  1) no action, 2) fences without wildlife crossings and 3) fences combined with wildlife crossings. Their objective was to maximize the expected number of wildlife species persisting in their hypothetical landscape with habitat patches subject to wildlife mitigation measures and separated by roads. Three different planning strategies were tested: 1) single species, 2) two focal species with different life history traits and 3) comprehensive multispecies planning. The authors then performed a trade-off analysis between the probability of persistence of each wildlife population and total mitigation costs.

The single species strategy was found to be very inefficient, while multispecies planning strategy was seen to maximise the number of persisting species. It also provides the most robust and cost-effective planning strategy in the study. Focal species with the largest home range can provide a reasonably cost-effective result when there is not enough time, money or insufficient information to perform a multispecies analysis.

In a world of expanding road networks, declining biodiversity and limited resources available for conservation, suitable tools for road mitigation are essential. Although it uses a hypothetical landscape and mostly Australian species set, this article by Polak et al. represents an important advancement where systematic planning can be applied to choose the most cost-effective measure and reduce the impacts of road networks on wildlife populations. It will be now exciting to see how this approach can be applied to other landscapes, in more complex situations and with different species sets.

Read the full article, Optimal planning to mitigate the impacts of roads on multiple species in Journal of Applied Ecology.