Roads pose a roadblock to tiger conservation in South and Southeast Asia

Study finds proposed road construction in the continent could impact tiger populations in 13 countries.

At the beginning of the 20th century, the large-scale production of automobiles revolutionised transport and today, most aspects of daily life depend on these wagons on wheels. With an increase in the number of vehicles came an unquenchable thirst for building roads across the world. It is now predicted that by 2050, the planet could see up to 4.7 million kilometres of roads— more than ten times the distance between the Earth and the Moon! A new study now shows that tigers could be an unfortunate victim of this unprecedented surge in road construction as more roads are making inroads into their natural habitats. 

The study, published in the journal Science Advances, calculates the impacts of road networks across thirteen countries in South and Southeast Asia, which are home to the globally endangered tiger (Panthera tigris). It found that about 134,000 km of roads are found across regions which are tiger habitats, including protected areas. 

Dr Neil Carter, Assistant Professor at the University of Michigan and the corresponding author of the study was alarmed by the extent of road and rail construction in Nepal and the rest of South Asia. “I soon discovered that Asia was experiencing a road-building boom”, he says, adding that many were around tiger habitats in Nepal.

"I became interested in understanding how many roads are in tiger habitats, and was considering ways for making road development more sustainable in the future," he shares. 

Roads are an obvious problem for wildlife for many reasons.

"Roads can affect wildlife by acting as barriers to movement and reducing gene flow," explains Dr Carter. Roadkills, where animals are struck down by moving vehicles, is a significant concern in India and elsewhere.

Statistics show that between 2015-2017, about 10 tigers were killed in India due to vehicle collisions.

"Roads also facilitate human settlement growth, natural resource extraction, and hunting and illegal harvest," he adds.

Studies in the past, albeit few, have documented the impacts of roads on tiger populations. They have found to have higher mortality near roads, and their young are less likely to survive near roads. When roads cut across protected tiger habitats, they create "tiger islands" where the populations become isolated, leading to a decreased diversity in their gene pool. Besides, the availability of fewer prey animals near roads affect their abundance too.

Roads as roadblocks

The current study used a recently developed dataset of roads across the world to find out how much of them influenced tiger habitats in 13 countries in South and South Asia. These included protected areas, identified priority sites for doubling tiger populations and tiger conservation landscapes. They calculated the road density, distance to the nearest road and the abundance of mammals, like tigers and their prey, near the roads. This analysis also included roads proposed and under construction, like China’s Belt and Road Initiative (BRI).

The study found that road densities varied considerably across countries and on an average, was about 34% higher in areas that are not protected by regulations. In some countries, like Cambodia and Malaysia, road densities were higher in protected areas than in unprotected areas. In India, the densities were about the same in both protected and unprotected areas. The highest road density was at 628 m/km² in the Rajaji National Park of Uttarakhand. More than half of the tiger habitats in South and Southeast Asia were found to be within five kilometres from the nearest road.

The findings also showed that the abundance of mammals decreased by about 20% in areas where roads were present. Some regions, identified as tiger breeding areas, were found to have extensive road networks, with 14% of this area having less than half of mammal abundance as compared to regions undisturbed by roads. The researchers predict that by 2050, a whopping 24,000 km of roads will be constructed in tiger conservation areas. India, which has the most number of wild tigers in the world, tops the list. It is predicted that by 2050, 14,500 kilometres of roads will pass through tiger habitats—a 32% increase from the current levels.

Map of estimated road densities for the 76 Tiger Conservation Landscapes. The bar graph shows road densities in the protected and unprotected portions of these TCLs for each of the 13 countries. [Image Credits: Carter et al., Sci. Adv. 2020]

The road ahead

Construction of roads has been dubbed a signature of progress, and India is no stranger to the clash between this perceived development and conservation.

“Once roads are built, they have lasting impacts on ecosystems and biodiversity,” says Dr Carter. But what about livelihoods and welfare? “Humanity relies on healthy ecosystems, and therefore maintaining their health also supports social welfare. I don't think we should underestimate what is lost when ecosystems and biodiversity are degraded by roads. A better accounting of these cumulative, long-term impacts from road development can facilitate more sustainable infrastructure planning”, he argues.

The researchers of the study also suggest a few policy decisions that can help in planning sustainable road construction. Massive multinational projects, like the BRI, can adopt biodiversity conservation as one of its core values since most participating countries are signatories on the Convention on Biological Diversity and are bound to protect tiger habitats.

“That would set the stage for the BRI to plan and implement a network of protected areas and wildlife corridors that help meet, or exceed, the Convention on Biological Diversity’s targets for protection and safeguard tigers from the impacts of roads,” says Dr Carter.

Funding agencies, like the Asian Development Bank and World Bank, should mandate impact assessments of infrastructure projects, recommends the study.

Where would that leave India, which tops the list of tigers and roads into their habitats?

“I'd recommend that India embrace tiger-friendly infrastructure planning, which includes prohibiting road development from priority tiger populations and other “no go” zones, such as tiger reserves or habitat corridors,” says Dr Carter. Assessing the impacts of roads on increased hunting and poaching of tigers and their prey is vital too. “Screening proposed road developments by these tiger-friendly criteria should be done very early before it is too late to influence road planning,” he recommends.

For existing roads, banning vehicular traffic at night, closing roads in areas with significant tiger populations, road signs and construction of wildlife crossings can help, suggests the study.