More roads, fewer tigers, study suggests

Nearly 24,000 kilometres of new roads will be built in Asian tiger habitat by mid-century, potentially increasing the risk of the animal’s extinction, according to a new study.

Researchers led by conservation ecologist Neil Carter, from the University of Michigan, US, used a new global roads dataset to calculate the extent and potential impact of existing and planned road networks in 13 countries.

Road construction often exacerbates all three of the main threats to tigers – prey depletion, habitat degradation and poaching – they write in a paper in the journal Science Advances.

But, they add, major projects such as China’s Belt and Road Initiative (BRI) could be partners in tiger preservation by adopting biodiversity conservation as a core value.

Carter and colleagues say there are already 134,000 kilometres of roads in Tiger Conservation Landscapes (TCLs) – blocks of habitat that are considered crucial for recovery of the species. 

In all, 43% of the area where tiger breeding occurs and 57% of the area in TCLs are within five kilometres of a road.

Road densities are, on average, 34% greater in unprotected portions of TCLs than in strictly protected parts, indicating that road density increases with the relaxation of protection status.

But densities vary widely between countries. China’s mean road density in TCLs is nearly eight times greater than Malaysia’s, for example.

“Tiger habitats have declined by 40% since 2006, underscoring the importance of maintaining roadless areas and resisting road expansion in places where tigers still exist, before it is too late,” says Carter. 

Despite a broad commitment to protect tigers, exemplified by an international initiative called TX2, few studies have assessed the impacts of roads on tigers and their recovery, Carter adds, thus hampering conservation planning.

Most previous studies have focused on localised patterns of wildlife mortality or behaviour associated with road design, rather than specifically estimating the impact of roads at broad scales.

“This research opens the door to build partnerships at the regional scale to better mitigate existing roads and to develop greener road designs for the next century of infrastructure development,” says co-author Adam Ford, from the University of British Columbia, Canada.

The researchers say their metrics provide tools to support sustainable road development, enabling rapid risk assessment for roads passing through tiger habitat, including roads planned as part of the BRI.