Severe conservation risks of roads on apex predators

A study in nature conducted by a team of international researchers from Spain, Colombia, South Africa, Guatemala, Brazil, Nepal, and France assessed the risks of roadways to top predators and found that, of the 10 most at-risk predators, two occur in South America. The Andean bear currently suffers from habitat fragmentation due to the high density of linear infrastructure in the north of the Andes mountain range. By inhabiting open ecosystems, the maned wolf is greatly affected by mortality on the roads. Particularly in the Brazilian Cerrado, more than 900 maned wolves have been killed by collision since 1994.

Other top predator species inhabiting the Americas are not at extreme risk from roads today, thanks to their broader distributions in areas such as the Amazon Basin. The Amazon is currently one of the largest roadless areas in the world; however, the proposed road expansion includes 16,700 km of new roads and the paving of another 19,800 km of existing gravel roads.

This study shows that, if built as planned, almost all of the proposed 36,500 km of highways in the Amazon will be built within the range of pumas, ocelots, and jaguars (see Figure). In addition, future highways will cross 175 protected areas, including indigenous lands and sustainable use reserves. One of the largest tropical forest national parks, the Tumucumaque mountains, will be crossed by 700 km of new roads. These developments will promote rapid forest loss and push the frontiers of deforestation, which will affect populations of top predators with a high affinity for closed-canopy forests, such as jaguars, ocelots, and pumas. Unfortunately, the proposed highways will increase the mortality of these species, increasing the risk of being run over and poached.

The authors call for rigorous road development planning, avoiding natural areas and areas important for conservation. Simultaneously, future highways must adopt mitigation measures such as safe crossing zones for wildlife.

The figure shows the potential impact of future highways in the Brazilian Amazon. The bubble sizes indicate the percentage of road length belonging to each impact level. The bar graphs show the impact of future roads on top predators: the length of future roads (FRL) that will cross the range of the species and the proportion of length in relation to the total distribution of the species. The percentage next to the bars indicates the percentage of the road length that crosses the distribution of the species in relation to the total length of road development. All silhouettes were purchased from PhyloPic (http://www.phylopic.org/).

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