Endangered tigers face growing threats from an Asian road-building boom



Female tiger crossing track, Bandavgarh National Park, India.
David Tipling/Universal Images Group/Getty Images

Neil Carter, University of Michigan

Tigers are one of the world’s most iconic wild species, but today they are endangered throughout Asia. They once roamed across much of this region, but widespread habitat loss, prey depletion and poaching have reduced their numbers to only about 4,000 individuals. They live in small pockets of habitat across South and Southeast Asia, as well as the Russian Far East – an area spanning 13 countries and 450,000 square miles (1,160,000 square kilometers).

Today Asia is experiencing a road-building boom. To maintain economic growth, development experts estimate that the region will need to invest about US$8.4 trillion in transportation infrastructure between 2016 and 2030.

Major investment projects, such as China’s Belt and Road Initiative – one of the largest infrastructure projects of all time – are fueling this growth. While roads can reduce poverty, especially in rural areas, many of Asia’s new roads also are likely to traverse regions that are home to diverse plants and animals.

To protect tigers from this surge of road building, conservation scientists like me need to know where the greatest risks are. That information, in turn, can improve road planning in the future.

In a newly published study, I worked with researchers at the University of Michigan, Boise State University and the University of British Columbia to examine how existing and planned Asian roads encroach on tiger habitats. We forecast that nearly 15,000 miles (24,000 kilometers) of new roads will be built in tiger habitats by 2050, and call for bold new planning strategies that prioritize biodiversity conservation and sustainable road development across large landscapes.

Economic growth in Asia means more roads will be built into tiger habitat. Planning at the outset can make these projects more tiger-friendly.

Letting humans in

Road construction worsens existing threats to tigers, such as poaching and development, by paving the way for human intrusion into the heart of the tiger’s range. For example, in the Russian Far East, roads have led to higher tiger mortality due to increased collisions with vehicles and more encounters with poachers.

To assess this threat across Asia, we focused on areas called Tiger Conservation Landscapes – 76 zones, scattered across the tiger’s range, which conservationists see as crucial for the species’ recovery. For each zone we calculated road density, distance to the nearest road and relative mean species abundance, which estimates the numbers of mammals in areas near roads compared to areas far from roads. Mean species abundance is our best proxy for estimating how roads affect numbers of mammals, like tigers and their prey, across broad scales.

We also used future projections of road building in each country to forecast the length of new roads that might be built in tiger habitats by 2050.

Overpasses and underpasses, like this one in Florida, help wild animals traverse highways safely.

More roads, fewer animals

We estimated that more than 83,300 miles (134,000 kilometers) of roads already exist within tiger habitats. This is likely an underestimate, since many logging or local roads are missing from the global data set that we used.

Road densities in tiger habitat are one-third greater outside of protected areas, such as national parks and tiger reserves, than inside of protected areas. Non-protected areas averaged 1,300 feet of road per square mile (154 meters per square kilometer), while protected areas averaged 980 feet per square mile (115 meters per square kilometer). For tiger populations to grow, they will need to use the forests outside protected areas. However, the high density of roads in those forests will jeopardize tiger recovery.

Protected areas and priority conservation sites – areas with large populations of tigers – are not immune either. For example, in India – home to over 70% of the world’s tigers – we estimate that a protected area of 500 square miles, or 1,300 square kilometers, contains about 200 miles (320 kilometers) of road.

Road networks are expansive. Over 40% of areas where tiger breeding has recently been detected – crucial to tiger population growth – is within just 3 miles (5 kilometers) of a nearby road. This is problematic because mammals often are less abundant this close to roads.

In fact, we estimate that current road networks within tiger habitats may be reducing local populations of tigers and their prey by about 20%. That’s a major decrease for a species on the brink of extinction. And the threats from roads are likely to become more severe.

Estimated road densities for 76 tiger conservation landscapes (colored zones), with darker red indicating more roads per unit area.
Neil Carter, CC BY-ND

Making infrastructure tiger-friendly

Our findings underscore the need for planning development in ways that interfere as minimally as possible with tiger habitat. Multilateral development banks and massive ventures like the Belt and Road Initiative can be important partners in this endeavor. For example, they could help establish an international network of protected areas and habitat corridors to safeguard tigers and many other wild species from road impacts.

National laws can also do more to promote tiger-friendly infrastructure planning. This includes keeping road development away from priority tiger populations and other “no go” zones, such as tiger reserves or habitat corridors.

Zoning can be used around infrastructure to prevent settlement growth and forest loss. Environmental impact assessments for road projects can do a better job of assessing how new roads might exacerbate hunting and poaching pressure on tigers and their prey.

Funding agencies need to screen proposed road developments using these tiger-friendly criteria before planners finalize decisions on road design, siting and construction. Otherwise, it might be too late to influence road planning.

There are also opportunities to reduce the negative effects of existing roads on tigers. They include closing roads to vehicular traffic at night, decommissioning existing roads in areas with important tiger populations, adding road signs announcing the presence of tigers and constructing wildlife crossings to allow tigers and other wildlife to move freely through the landscape.

Roads will become more pervasive features in Asian ecosystems as these nations develop. In my view, now is the time to tackle this mounting challenge to Asian biodiversity, including tigers, through research, national and international collaborations and strong political leadership.

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Neil Carter, Assistant Professor of Wildlife Conservation, University of Michigan

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Some good conservation news: India’s tiger numbers are going up



Spotting tigers in the wild is a difficult task.
Author provided

Matt Hayward, University of Newcastle and Joseph K. Bump, University of Minnesota

Indian tiger numbers are up, according to one of the most detailed wildlife surveys ever conducted. Tiger populations have risen by 6%, to roughly 3,000 animals.

The massive survey may set a new world standard in counting large carnivores. The encouraging results validate India’s impressive investments in tiger conservation.




Read more:
Tigers confirmed as six subspecies, and that is a big deal for conservation


A mammoth effort

Large, solitary predators hate being seen. They owe their entire existence to being able to avoid detection by prey and sneak close before attacking.

Hence, when we want to count tigers, the tigers don’t help. But accurate population numbers are fundamental to good conservation. Every four years since 2006, the Indian government conducts a national census of tigers and other wildlife.

The efforts the project team undertakes to derive the tiger population estimate are nothing short of phenomenal: 44,000 field staff conducted almost 318,000 habitat surveys across 20 tiger-occupied states of India. Some 381,400 km² was checked for tigers and their prey.

(There is an application in with the Guinness Book of World Records to see if this is the largest wildlife survey ever conducted anywhere in the world.)

The team placed paired camera traps at 26,760 locations across 139 study sites and these collected almost 35 million photos (including 76,523 tiger and 51,337 leopard photos). These camera traps covered 86% of the entire tiger distribution in India. Where it was too dangerous to work in the field (14% of the tigers’ distribution) because of political conflict, robust models estimated population numbers.

Millions of photos were analysed to create an accurate count of India’s tiger population.
Author provided

Count the tigers

Collecting this volume of data would be an utter waste of time if it were poorly analysed. The teams took advice from some of the world’s foremost experts to sort the photos: pattern matching experts who could identify whether a photo of a tiger taken in the monsoon matched that of a tiger taken in the dry season while walking at a different angle, machine learning experts to speed up species identification, and spatial analysis experts to estimate the populations of tigers and their prey.

The research team took this advice and coupled it with their own knowledge of tiger ecology to develop a census that is unique among large carnivore studies.

We were fortunate enough to be among the non-Indian scientists invited to review this process. Peer review is a crucial part of any scientific endeavour, and especially important as early Indian tiger surveys were notoriously unreliable.

Actual numbers

So how did they do? A total of 2,461 individual tigers older than one year of age were photo-captured. The overall tiger population in India was estimated at 2,967 individuals (with an error range of roughly 12%).

Out of this, 83.4% were estimated from camera-trap photos, and the rest estimated from robust modelling. Tiger numbers have increased by 6% per year, continuing the rate of increase from the 2014 census. This is a wonderful success for Indian conservation efforts.

However not all is rosy. There has been a 20% decline in areas occupied by tigers in 2014 to today, although tigers have moved into some new areas (some 8% of their Indian range is new). The coordinators of the tiger survey – Yadvendradev Jhala and Qamar Qureshi – conclude that while established and secure tiger populations in some parts of India have increased, small, isolated populations and those along corridors between established populations have gone extinct.

This highlights the need for conservation efforts to focus on improving connectivity between isolated populations, while incentivising the relocation of people out of core tiger areas, reducing poaching and improving habitat to increase prey resources.

This will be no easy task with India’s burgeoning population, but investment from private sector tourist corporations in land acquisition along corridors and the creation of community conservancies could supplement government funding for expanding protected corridors.




Read more:
Curious Kids: why do tigers have whiskers?


The success of India’s census has led the governments of Nepal and Bangladesh to employ the same project team to help estimate their own tiger populations. These methods can – and should – be employed for other iconic, charismatic species that can be individually identified, such as jaguars in South and Central America; leopards, cheetahs, and hyenas in Africa, and possibly even quolls in Australia.


This article was co-authored by Chris Carbone, Senior Research Fellow at the Zoological Society of London.The Conversation

Matt Hayward, Associate professor, University of Newcastle and Joseph K. Bump, Associate Professor, Gordon W. Gullion Endowed Chair in Forest Wildlife Research and Education, University of Minnesota

This article is republished from The Conversation under a Creative Commons license. Read the original article.