Data from: A few large roads or many small ones? How to accommodate growth in vehicle numbers to minimise impacts on wildlife

Roads and vehicular traffic are among the most pervasive of threats to
biodiversity because they fragmenting habitat, increasing mortality and
opening up new areas for the exploitation of natural resources. However,
the number of vehicles on roads is increasing rapidly and this is likely
to continue into the future, putting increased pressure on wildlife
populations. Consequently, a major challenge is the planning of road
networks to accommodate increased numbers of vehicles, while minimising
impacts on wildlife. Nonetheless, we currently have few principles for
guiding decisions on road network planning to reduce impacts on wildlife
in real landscapes. We addressed this issue by developing an approach for
quantifying the impact on wildlife mortality of two alternative mechanisms
for accommodating growth in vehicle numbers: (1) increasing the number of
roads, and (2) increasing traffic volumes on existing roads. We applied
this approach to a koala (Phascolarctos cinereus) population in eastern
Australia and quantified the relative impact of each strategy on
mortality. We show that, in most cases, accommodating growth in traffic
through increases in volumes on existing roads has a lower impact than
building new roads. An exception is where the existing road network has
very low road density, but very high traffic volumes on each road. These
findings have important implications for how we design road networks to
reduce their impacts on biodiversity.

道路与机动车交通是对生物多样性最普遍的威胁之一，因其会破坏栖息地的连续性、提高死亡率，并为自然资源的开发开辟新区域。然而，道路上的车辆数量正迅速增长，且这一趋势在未来可能持续，给野生动物种群带来更大压力。因此，一个主要挑战在于规划道路网络以适应车辆数量的增长，同时最大限度减少对野生动物的影响。尽管如此，目前我们几乎没有可指导现实景观中道路网络规划决策以降低对野生动物影响的原则。我们通过开发一种方法来解决这一问题，该方法可量化两种适应车辆数量增长的替代机制对野生动物死亡率的影响：（1）增加道路数量；（2）提高现有道路的交通流量。我们将此方法应用于澳大利亚东部的考拉（Phascolarctos cinereus）种群，量化了每种策略对死亡率的相对影响。我们发现，在大多数情况下，通过提高现有道路流量来适应交通增长的影响低于新建道路。例外情况是现有道路网络密度极低，但每条道路的交通流量极高。这些发现对我们如何设计道路网络以降低其对生物多样性的影响具有重要意义。