Finding a middle path: While roads and highways are indeed critical for development, those passing through forests cause heavy collateral damage

by Pavithra Sankaran & M. D. Madhusudan

The gaur have been trying to cross the highway for a while now. They stand in an alert huddle, their dark coats gleaming in the headlights of trucks and cars passing through Bandipur Tiger Reserve. This stream of traffic between Ooty and Bangalore seems unending and the speed limit seems irrelevant. Dusk falls fast and it is soon night. Forty-five minutes later, the gaur are still waiting for a pause in the traffic, simply to get across this ten-metre strip of road, in a Reserve where they are supposed to be able to roam fearlessly.

The road that brings vegetables to Calicut, tourists to Ooty and seafood to Bangalore also slashes the forests of Bandipur in two. On this narrow 15-kilometre strip of asphalt, the lives of thousands of animals–from dragonflies and deer to tortoises and tigers–have been lost under the wheels of passing vehicles. But the same road also allows hundreds of wide-eyed travellers, like us, to experience the beauty of a deciduous forest and catch a glimpse of its inhabitants.

To be sure, roads do serve the country and its people in critical ways. They are indicators of development, providing access to education, healthcare, markets and even a platform for people to hold protests simply by sitting on them and staging a rasta-roko.

But for a while now, conservationists in India have been holding their own form of rasta-roko. In several of our sanctuaries and national parks, roads have become the subject of much controversy. Thousands of kilometres of roads weave through our forests, posing all manner of threats to our wildlife. As gashes in the habitat, roads open up dense and closed forests to invasive plants, to pollution from vehicles and to the garbage that always trails people. Trees along roads are also known to die off faster because of exposure. Retaining walls and safety barricades make parts of the forest inaccessible to small animals like turtles, which are unable to cross these barriers and sometimes die trying. All this, of course, in addition to the roadkills that smoother roads and faster vehicles inevitably leave behind.

While standing together with conservationists in defending our parks against highway projects of other government agencies, the Forest Department is itself often involved in expanding road networks within reserves. Some length of dirt roads are certainly needed for patrolling and controlling fires, but some of our parks have a road density—one kilometre for each square kilometre of forest—that parts of rural India would certainly envy!

What conservationists have been asking for is a more thoughtful planning of roads through forested areas. The Mysore-Mananthavady highway through Nagarhole Tiger Reserve is a case in point. A World Bank funded project to widen and resurface the highway raised concerns about the safety of wildlife in the Reserve. Rather than simply oppose the road, conservationists and local people suggested a diversion that skirted the forest instead of cutting through it. For a small increase in budget and a three-kilometre increase in length, this diversion would also provide highway access to 11 villages along the Reserve boundary. The alternative plan, predictably, was resisted by the government and only after protracted negotiation, finally approved.

Just as we have set limits on what we can take out of our forests, mustn’t we also watch what we put in them? Evidence for the damage that intrusions like highways, pylons, canals and pipelines cause to our sensitive natural areas and their wildlife is indeed compelling. What we need now is a strong and clear policy to regulate their construction and ensure that, while getting the infrastructure our country needs, we do not fray the fabric of our forests further.

An edited version of this article appeared in The Times of India dated 28th January 2011

An endangered lion-tailed macaque lies dead on the road in a rain forest fragment in the Western Ghats. (Photo: Kalyan Varma)

Crunch! Splat! Thud! A daily massacre is occurring under the wheels of our vehicles. Thousands of lives are snuffed out tragically, instantaneously, and yet, we hardly notice.

Around India, as in other parts of the world, millions of animals risk daily encounter with increasingly fast vehicles plying on an expanding meshwork of roads and highways. Roads through our countryside and forests and the people who drive vehicles on these routes cause the highest toll. This is a toll of actual lives—a headcount of animals crushed to death or else greviously injured and mutilated. Even leaving aside domestic dogs and cats, an indiscriminate diversity of wild species from butterflies, squirrels, lizards, and partridges to more threatened species such as leopard cats to tigers and lions, mouse deer to sambar and elephant, lorises to langurs and lion-tailed macaques, and sheildtail snakes to king cobras come to a sticky end.

The scale of the problem is imposing. India boasts of having the second largest road network in the world, second only to the United States. According to India’s National Economic Survey of 2007 ― 08, this is no less than 3.34 million kilometres [1]. Although only around half of this is surfaced and less than 2 percent of this comprises National Highways, the latter alone account for 40% of our total traffic. Like many things in India, the ‘total’ in that expression is a very large number indeed. In 2006, India already had around 86 million registered motor vehicles. A study [2] from IIM, Lucknow, records that the distance travelled in a year by a person in India (averaged across the entire population) soared from 285 km in 1950 — 51 to 3,470 km in 2000 — 01. At the time of writing, even this has nearly doubled. The study also estimates a staggering total motorized traffic volume of around 5,600 billion passenger-kilometres per year, currently. With an annual rate of increase hovering around 7 – 8%, this is poised to skyrocket to nearly 13,000 billion passenger kilometres by 2020.

With such traffic, it would be scarcely surprising if animal kill rates were high, too. Roads passing through forest and other natural areas such as grasslands and wetlands are of greater concern from a conservation point of view. The few studies that are available from Indian forests indicate a grave situation already. Studies have documented kills ranging from dragonflies and butterflies, to many larger mammals and birds including carnivores [3]. Around noon in Nagarahole – Bandipur in southern India, as 50 – 100 vehicles zip past every hour, a study patiently documented around 40 kills of insects such as butterflies and dragonflies for every 10 km every day, doubling over the weekends with increased traffic. A rough calculation indicates that vehicles here kill around 15,000 animals every year in just that 10 km of road [4]. In the Anamalai hills of southern India, a study of road kills of reptiles and amphibians found that around 6 were killed per 10 km of road every day during the monsoon [5]. Conservative extrapolation would suggest that a 100 km stretch of road through forests here witnesses an annual slaughter of around 10,000 amphibians and reptiles. Even this estimation is based on a study carried out 10 years ago when traffic volumes were much lower. Widening of roads and unregulated, ill-planned tourist influx has, if anything, made things worse.

Reptiles, such as this vine snake, and amphibians are among the worst hit in road kills. Photo: Kalyan Varma

Species struggle to survive

Such patterns of death on the highways are a common feature wherever roads traverse our forests, grasslands, and wetlands. Along the Western Ghats alone—a hill range much touted as a centre of amphibian and reptilian diversity with so many new species even now being discovered and described—hundreds of thousands are probably killed every year. These numbers should not make us proud that we have so many animals to subject to such wanton slaughter—that would merely be a dangerous assumption, a form of denial, or sheer ignorant optimism. Neither can we take heart from areas where few deaths are now seen along roads, until we can be certain that this is not due to populations having already been pushed over the brink.

Planners and managers neglect to take the problem seriously. Even when they are aware of the issue, they feel nothing needs to be done because they believe that while many are killed on roads, many others escape and the species can survive. What they fail to understand is that the additional mortality on roads can tilt the demographic scale against a population that already grapples with various natural factors and human-caused disturbances for survival. Studies from elsewhere have revealed that the negative effects of high traffic density can be as serious as direct loss of forest cover for amphibians and traffic needs to be avoided or maintained at low density for up to 2 km around breeding ponds if frog diversity is to be conserved in the landscape [6]. Another study estimates that even if 10% or more of the adults annually risk being killed by vehicles along roads near breeding areas, the population will eventually perish [7].

In most cases, all that the animal is trying to do is, like the proverbial chicken, to get to the other side. The road surface and corridor itself is of little use to most animals. Perhaps a dove or myna would find some fallen scraps of food worth eating, a lizard or snake may be attracted to bask on the hot surface, as to a rock on a sunny day. Dragonflies and mayflies may be attracted to the polarized light emanating from the asphalt, a form of light pollution that fools them into believing that they are over the surface of a water body [8]. As they fly around to feed or defend territories or even try to lay eggs on the water-road, they imperil their own survival. And then the road becomes an ecological death-trap [9], where the very adaptations evolved over millenia to enable these species to locate their food and thrive in their environment now nudge them to their death.

Even quick-footed species, such as this leopard cat, get killed with the increasingly faster traffic. Photo: Kalyan Varma

Deadly break in tree cover

The roadkill threat is not something only ground-dwelling face. The threat of roadkills is particularly acute for many tree-dwelling species that do not normally cross on the ground. With roads mercilessly slicing through our forests and government departments and road contractors recklessly widening roads and slashing all vegetation, including regenerating trees and saplings on either side, the tree cover breaks over the road. Besides loss of natural vegetation and native species typical to each area, this causes increased soil erosion and landslides. This leads to further expenditure in road maintenance—providing further opportunity for ecological damage. All of this adds to wastage of public money, while also wrecking the tree cover that would have allowed many species to safely cross the road overhead.

Unable to cross overhead using the overlapping branches of intact forest canopies, the animals now face a permanent problem—a serious, life-threatening challenge—of a gap caused by the break in tree cover over the road. That crossing, even if takes only a few seconds or minutes, can be an agonisingly long and threatening one for an animal trying to cross even a moderately busy road. In the absence of tree cover, arboreal animals are sometimes forced to use electric wires of powerlines to cross, leading to the double jeopardy of electrocution deaths for species such as lorises and lion-tailed macaques [10]. The roads and powerlines through our forests are increasingly turning into graveyards of tree-dwelling species such as monkeys, lorises, civets, squirrels, and tree shrews.

Animals may also be seriously stressed or change their behaviour in the vicinity of roads. Studies from Africa on elephants and chimpanzees, have shown how they tend to avoid roads and change their behaviour, due to the associated risks as one would expect from such highly intelligent species [11].

An elephant mother uses her body to shield her calf from an approaching vehicle as they cross the road. Photo: Kalyan Varma

Other factors may compound the road problem. The building of culverts, fencerails, barricades, chain-link and barbed-wire fences, and other concrete and metal structures along roads makes the crossing even more difficult. Parapet-like walls running without a break for hundreds of metres or kilometres along roads, especially on hill roads, become insurmountable obstacles for species such as porcupines, pangolins, turtles, young birds and mammals, to name just a few. On hill slopes disfigured by such roads, even large animals such as sambar and elephants have to negotiate the upper slope, cross the road, and try to somehow step or jump over roadside walls and culverts to step or land safely on the steep lower slope. Another compounding factor is the attraction of animals to road-killed carcasses, which may lead to further deaths from speeding vehicles until the carcass is safely disposed away from the road.

As roads become wider and busier, the number of animals crossing and the rate of roadkill usually increases, but beyond a point it may actually begin to decrease [12]. This usually happens when roads become four-laned highways or expressways catering to tens of thousands of vehicles every day. The reduction may be due to the decimation of wildlife populations along the road as well as a ‘barrier’ effect, where many animals actively avoid the road and avoid crossing it [13]. A road like this passing through a forest or key natural habitat essentially cleaves it into two pieces. For many species, this is an added fragmentation of an already fragmented habitat [14].

Impact of ecological changes

In addition, roads are now well known to cause various ecological changes, leading to a wide range of impacts including many, often unnoticed, detrimental effects on wildlife [15]. The disturbance associated with roads and the opening created by the road corridor does favour some species; unfortunately, these are mostly undesirable ones. Alien weeds spread along roads using them as highways to invade into ecosystems [16]. The exposure along the road dessicates and dries vegetation, making it more prone to fires. Trees are more exposed, too, and may fall due to high wind speeds along the road or suffer from stress related to altered ecology. All of these contribute to permanent and chronic changes in the environment and habitat, thereby affecting wildlife and ecosystem health.

Yet, this is only a small part of the story. No study has yet comprehensively addressed all animal taxa from invertebrates such as snails and ants to large creatures such as peafowl and elephants. Even the studies carried out so far may underestimate the true damage. Many animals are struck and badly wounded by vehicles along roads but manage to flee or drag themselves away from the road corridor to die unseen and unrecorded by researchers some distance away. It is not unusual for road-killed animals to be removed off the road or consumed by scavengers, including people, and thereby the kills go unrecorded. Even when dead animals on the road are noticed, other pervasive problems related to the road within forest areas are overlooked. This includes animals killed during road construction, earthwork and annual maintenance operations, particularly slow-moving and burrowing species such as turtles, snakes, and soil fauna.

Poor data on forest roads

No study has yet even catalogued the extent of roads through natural areas, especially forests, across India or the loss of forest cover due to roads. A notable exception, from Garo Hills in Meghalaya, showed that just in this region the 456 ha of biodiversity-rich forest was lost to roads between 1971 and 1991 [17]. Another long-term aspect is the issue of increased access: people moving in and settling or polluting otherwise remote areas.

While more studies on road ecology are required in India, there is also urgent need to use existing information and experiences from other countries to begin to reduce and avoid this carnage [18]. This requires the immediate attention and close coordination of ministries and departments related to roads and forests (or other natural ecosystems). Most important, it requires the attention of the citizen, the casual driver, the tourist—particularly the vehicle-based ‘eco-tourist’—whose individual initiative, sensitivity, and care could save thousands of animal lives.

A range of measures could help remedy the situation. Some are merely engineered quick-fixes that can help in certain locations or in the short-term, such as artificial ‘canopy bridges’ for movement of arboreal mammals [19]. Other measures include proper deployment of speed breakers in roads through forests, creation of underpasses and overpasses that are well-designed keeping in mind the ecology and behaviour of the species whose mortality rate is sought to be mitigated. Signboards informing people to look out for and allow wildlife to cross and measures to check overspeeding may also be implemented. Such short-term measures, if implemented based on research that has identified roadkill ‘hotspots’ can have very positive effects. For example, the installation of just four speed-bumps along 1.5 km of highway passing through a forest in Zanzibar, helped reduced the mortality of threatened red colobus monkeys by 85% in first nine months itself. Prior to this, every year, vehicles used to kill 15% of the colobus monkey population living near the road [20]. Slowing down vehicles at key locations is a very crucial aspect that reduces likelihood of road kill while providing greater reaction time for drivers and animals to evade a collision.

Longer-term and more sustained measures require a deeper understanding of the landscape through which roads pass and a greater sensitivity to the species we share this world with. The number, extent, and width of roads passing through forests and wetlands should be strictly regulated. Improvements to the quality of the road surface and adequate signages should be the emphasis for driver comfort and safety, not increasing the number of lanes or width of the road or the speed with which vehicles can traverse these crucial stretches. As there is virtually no understanding of these issues among planners, land managers, and the wider public, despairing conservationists today regard narrow, bad roads as a great boon, one that is surpassed only by the complete absence of roads.

Encourage vegetation growth

A key long-term measure is to encourage natural vegetation on either side of the road. Currently, vast amounts of public money is wasted in slashing all vegetation on either side of thousands of kilometres of road, with the spurious claim that this improves visibility or makes the road safer. In fact, dense weed growth rapidly chokes up the opened spaces on roadsides, replacing more pleasing and open, natural, native vegetation. In forest areas where tree cover would have naturally shaded out weed growth—performing a public service at no cost and with considerable aesthetic benefits—the opened spaces with obnoxious weed growth now represent a wasteful annual cost of repeated slashing in the guise of road maintenance. The lack of any understanding that good, stable, and safe roads really need consideration of ecological aspects as well, is one of the glaring failings of the government and road construction companies.

An example of a good forest road, used even by trucks and buses, with unbroken canopy over the road. Photo: NCF

The design and adoption of regulations is urgently needed. Forest roads should mandatorily retain and maintain tree canopy connectivity over the road. Where such connectivity has been lost, at a minimum, for every 200 metres of road, a 50-m-wide stretch needs to be marked off with signs and speed breakers and the tree canopy with overlapping branches re-established overhead. Efforts to establish and maintain such stretches should begin as a top priority along all roads through our wildlife sanctuaries, national parks, tiger reserves, reserved forests, and their buffer zones.

Guidelines need to be involved keeping specific species and landscape considerations in mind. For instance, in tropical forests of equatorial Africa, the home of the highly endangered great apes (gorillas and chimpanzees), the IUCN has prepared best-practice guidelines on a range of issues, including road planning [21]. This includes recommendations to plan roads at least 5 km away from protected area boundaries, reduce road width of primary roads to less than 7.5 m (less than 12.5 m including graded portion and shoulders) and width of secondary roads to less than 4.5 m (8.5 m including shoulders), avoiding road construction in closed-canopy forests, minimising the number of secondary roads, and re-using old roads rather than build new roads. There has been some effort to develop such guidelines in India [22], but there is much more to be done.

Forest areas around the world, including in India, are transected by a large number of old, unused, and unnecessary roads (e.g., old logging coupe roads, roads built during dam construction, or as ‘game’ roads for hunting). It is time to undo the damage wrought by these roads by actively removing these roads and ecologically restoring natural vegetation. Although the methods available for road removal may cause some short-term disturbance, research has clearly established the conservation benefits in the medium- and long-term [23].

An overarching need, although perhaps the most difficult one, is the sensitisation and involvement of individual drivers. A vast majority of drivers probably have no deliberate will to kill animals. They presumably have no wish to cause lasting harm to the environment or to the public exchequer by insisting on roads made and managed by ecologically illiterate and insensitive agencies. When individuals become aware and begin to care it can have two useful effects. As drivers, they can adopt more responsible driving practices, watch out for and respect animal crossings, and avoid other unsavoury practices such as feeding animals by roadsides. This, as a direct contribution, can help save hundreds to thousands of animal lives over an average driver’s lifetime. Second, by example, by persuasion, or ultimately by their vote in a ballot box, they can indirectly influence others to save thousands of lives, minimise ecological damage, help to improve roads, and make the driving experience along roads through natural areas infinitely more pleasant. When the paths of people and animals cross, each can then go their own way, leaving behind not a flattened carcass but the memory of a pleasant encounter.

Footnotes

[1] Economic Survey 2007-2008, Ministry of Finance, Government of India. Link accessed 17 April 2009.

[2] Singh, S. K. (2008) CO2 emissions from passenger transport in India: 1950-51 to 2020-21. Proceedings of the Better Air Quality 2008 Workshop, Bangkok, Thailand. Link accessed 17 April 2009.

[3] Chhangani, A. K. (2004) Frequency of avian road-kills in Kumbhalgarh Wildlife Sanctuary, Rajasthan, India. Forktail 20: 110-111.

Kumara, H. N., Sharma, A. K., Kumar, M. A., and Singh, M. (2000) Roadkills of wild fauna in Indira Gandhi wildlife sanctuary, Western Ghats, India: implications for management. Biosphere Conservation 3: 41-47.

Sundar, K. S. G. (2004). Mortality of herpetofauna, birds and mammals due to vehicular traffic in Etawah district, Uttar Pradesh, India. Journal of the Bombay Natural History Society 101: 392-398.

Radhakrishna,S. Goswami, A. B. and Sinha , A. (2006) Distribution and Conservation of Nycticebus bengalensis in Northeastern India. International Journal of Primatology 27: 971-982.

Areendran, G. and Pasha, M. K. S. (2000) Gaur Ecology Project, Report, Wildlife Institute of India, Dehradun.

Johnsingh, A. J. T., Sankar, K. and Mukherjee, S. (1997) Saving prime tiger habitat in Sariska Tiger Reserve. Cat News 27: 3-4.

[4] Rao, R. S. P. and Girish, M. K. S. (2007) Road kills: Assessing insect casualties using flagship taxon. Current Science 92: 830-837.

[5] Vijayakumar, S. P., Vasudevan, K. and Ishwar, N. M. (2001) Herpetofaunal mortality on roads in the Anamalai Hills, southern Western Ghats. Hamadryad 26: 265–272.

[6] Eigenbroda, F. Hecnarb, S. J., Fahrig , L. (2008) The relative effects of road traffic and forest cover on anuran populations. Biological Conservation 141: 35–46.

[7] Gibbs, J. P. and Shriver, W. G. (2005) Can road mortality limit populations of pool-breeding amphibians? Wetlands Ecology and Management 13: 281–289 .

[8] Horváth, G., Kriska, G., Malik, P. and Robertson , B. (2009) Polarized light pollution: a new kind of ecological photopollution. Frontiers in Ecology and the Environment 7; doi:10.1890/080129.

[9] Robertson, B. A. and Hutto, R. L. (2006) A framework for understanding ecological traps and an evaluation of existing evidence. Ecology 87: 1075-1085.

http://en.wikipedia.org/wiki/Ecological_traps

[10] Radhakrishnan, S. and Singh, M. (2002) Conserving the Slender Loris (Loris lydekkerianus lydekkerianus). Pages 227-231, National Seminar on Conservation of Eastern Ghats, March 24- 26, 2002, held at Tirupati, Andhra Pradesh; personal observations.

[11] Hockings, K. J., Anderson, J. R., Matsuzawa, T. (2006). Road crossing in chimpanzees: A risky business. Current Biology 16: R668-670. Watch movie here.

Blake, S., Deem, S. L., Strindberg, S., Maisels, F., Momont, L. Isia, I., Douglas-Hamilton, I.,Karesh, W. B., Kock, M. D. (2008) Roadless wilderness area determines forest elephant movements in the Congo Basin. PLoS ONE 3(10): e3546. doi:10.1371/journal.pone.0003546

[12] Seiler, A. (2003) The toll of the automobile: wildlife and roads in Sweden. PhD thesis. Swedish University of Agricultural Sciences, Uppsala. Link accessed 11 Feb 2009.

[13] Laurance, S. G. and Gomez, M. S. (2005) Clearing width and movements of understory rainforest birds. Biotropica 37: 149–152.

Laurance, S. G., Stouffer, P. C. and Laurance, W. F. (2004) Effects of road clearings on movement patterns of understory rainforest birds in Central Amazonia. Conservation Biology 18: 1099–1109.

Goosem, M. (2001) Effects of tropical rainforest roads on small mammals: inhibition of crossing movements. Wildlife Research 28: 351–364.

[14] Goosem, M. (2007) Fragmentation impacts caused by roads through rainforests. Current Science 93: 1587-1595.

See also this article by Rhett Butler on roads as enablers of rainforest destruction.

[15] Noss, R. The ecological effects of roads. Link accessed 17 April 2009;

Spellerberg , I. F. (1998) Ecological effects of roads and traffic: a literature review. Global Ecology and Biogeography Letters 7: 317-333;

Forman, R. T. T. and Alexander, L. E. (1998) Roads and their major ecological effects. Annual Review of Ecology and Systematics 29:207-231;

Trombulak, S. C. and Frissell, C. A. (2000) Review of ecological effects of roads on terrestrial and aquatic communities. Conservation Biology 14: 18-30;

Donaldson A. and Bennett A. (2004) Ecological effects of roads: implications for the internal fragmentation of Australian parks and reserves. Parks Victoria Technical Series No. 12. Parks Victoria, Melbourne.

Fahrig, L., and Rytwinski, T. (2009) Effects of roads on animal abundance: an empirical review and synthesis. Ecology and Society 14(1): 21.

[16] Gelbard, J. L. and Belnap, J. (2003) Roads as conduits for exotic plant invasions in a semiarid landscape. Conservation Biology 17: 420–432.

[17] Bera, S. K., Basumatary, S. K., Agarwal, A. and Ahmed, M. (2006) Conversion of forest land in Garo Hills, Meghalaya for construction of roads: a threat to the environment and biodiversity. Current Science 91: 281–284.

[18] Forman, R. T. T., Sperling, D., Bissonette, J., Clevenger, A., Cutshall, C., Dale, V., Fahrig, L., France, R., Goldman, C., Heanue, K., Jones, J., Swanson, F., Turrentine, T., Winter, T. (2002) Road Ecology: Science and Solutions. Island Press, Washington, D. C. Read review here.

http://www.wildlifeandroads.org

http://www.peopleandwildlife.org.uk/biblio.shtml#road

[19] Weston, N. (2002) Why did the ringtail cross the road? Using Rainforest Research, Cooperative ResearchCentre for Tropical Rainforest Ecology and Management, Australia.

Goosem, M., Izumi, Y. and Turton, S. (2001) Will underpasses below roads restore habitat connectivity for tropical rainforest fauna? Ecological Management and Restoration 2: 196–202. See also this article about faunal underpasses.

Laurance, W. F., Goosem, M. and Laurance, S. G. W. (in press) Impacts of roads and linear clearings on tropical forests. Trends in Ecology and Evolution in press.

[20] The Zanzibar Red Colobus Monkey: behavior, ecology, and conservation. DVD documentary, T. T. Struhsaker, Department of Biological Anthropology and Anatomy, Duke University, USA.

[21] Morgan, D. and Sanz, C. (2007) Best practice guidelines for reducing the impact of commercial logging on great apes in Western Equatorial Africa. IUCN SSC Primate Specialist Group (PSG), Gland, Switzerland. 32 pp.

[22] Rajvanshi, A., Mathur, V. B., Teleki, G. C., Mukherjee, S. K. (2001) Roads, sensitive habitats and wildlife: environmental guidelines for India and South Asia. Wildlife Institute of India, Dehradun.

[23] Switalski, T. A., Bissonette, J. A., DeLuca, T. H., Luce, C. H. and Madej, M. A. (2004) Benefits and impacts of road removal. Frontiers in Ecology and the Environment 2: 21-28.

A bird's eye view of Hollongapar Gibbon Wildife Sanctuary (Courtesy: Google Earth)

A death trap…

This railway track is an important one that connects several important commercial towns of upper Assam (Dibrugarh, Tinsukia, Digboi and Duliajan) to Guwahati and the rest of India. It was laid down during the 1930s basically to streamline the transportation of tea, coal, oil and important timbers from upper Assam to Guwahati. In this process the Hollongapar Gibbon Wildlife Sanctuary  became fragmented into two unequal chunks of forests. In addition to scores of other problems, this track has always posed a major threat to the wildlife of this isolated and fragmented 20.98 km2 sanctuary, most popularly known for its staggering primate community and possibly one of the highest primate density areas in the world.

Hollongapar Gibbon Wildlife Sanctuary showing the railway track in between two compartments (Courtest: Google Earth)

During one of the field-days, when I was venturing into the forest, I saw a troop of capped langurs feeding on the ripe fruits of Hoanlu (Litsea monopetala), a few of them on the tree and the rest on the ground along the railway line. On my way back in the evening, I hit upon something on the track. It was the carcass of a sub-adult capped langur, one of the members of the same troop that I saw feeding in the morning. This unfortunate individual probably forgot that speed is not its forte while on the ground.

A capped langur hit by a running train

For primates like the arboreal hoolock gibbon, which never descends to the forest floor, this track is an extreme barrier. There are three groups of hoolock gibbons, consisting of 11 individuals, which have been trapped in the smaller forest chunk of about 2 km2 (Compartment 1, as it is administratively known) of the sanctuary. Assuming that the population was trapped after the construction of railway line (in the 1930s) and the fact that the patch was already dismembered from the contiguous forest at the time of the construction, the gibbons are probably fighting their battle of survival in the patch for last 80 years!

The railway track

Amongst the other primates, the most terrestrial stump-tailed macaque and possibly the nocturnal slow loris never cross this track; this means that the resources readily available across the railway track always remains inaccessible to them. Only the rhesus macaque, owing to its mastery over ‘terrestrial matters’ is able to manage this deadly trap and a herd of 30-40 residential elephants perhaps! This herd crosses this track almost on a regular basis. Although it is heartening to know that no elephant death has ever been reported here, the credit for this must go to the elephant’s instincts, honed over million years of evolution, rather than to the lethargic forest department or the mindless train drivers for whom speed is too much to resist even as the track is dotted with elephant corridor signboards.

Death Trap-Rhesus macaque crossing the railway track

Besides these conspicuous and so-called ‘enigmatic’ animals, whose deaths invariably make news, there are numerous reptiles, amphibians and insects whose deaths go completely unnoticed, unannounced, forgotten. Even a causal walk along the track and you stumble upon the disfigured remains of hundreds of animal bodies scattered all around.

A rock python hit by a running train (Photo courtesy: Parimal Ch.Ray)

…and another

Meleng-Madhupur road

Besides the railway track, a road that runs through the sanctuary is another threat taking its toll on the wildlife of the sanctuary. This three kilometer road connects four villages adjacent to the sanctuary with the neighbouring Mariani town clogged with vehicles throughout the day. Recently this ‘deplorable’ road was repaired and was given a facelift to make it much ‘smoother’. It’s extremely agonizing to watch the reckless drivers testing their driving skills on it at a breakneck speed. The canopy above the road is wide open and it is frequently observed that arboreal primates and squirrels struggle to cross this gap. For reptiles and amphibians, crossing this gap of forest is not that an easy task, many lost their life in such attempts.

An unfortunate victim of road kill

Road ahead

Roads, railways and other linear infrastructures have made a pervasive incursion in most of the forest causing mortality of wildlife, severely disrupting animal movement, reduce the amount and quality of habitat and increase the risk of local extinction. The effect of these structures on the wildlife in some cases is glaring whereas in many it is very subtle.
To mitigate the problem of road kill and increase the permeability of roads to wildlife, management agencies and conservation organization are seeking engineering solutions. There is now an increasing use of rope bridge overpasses and various underpasses in providing connectivity to rainforest fauna worldwide.
Taking cue from such practices, the Assam Forest Department has been trying to construct two overpasses across the track in collaboration with the railways. Two steel ropes (wrapped in green plastic cover) were thus laid down over the track thus connecting two compartments. It was of course expected that the gibbons would use them and life would be fine again. It, however, just didn’t work. Nobody knows why or has made the effort to find out why. Probably the steel ropes were too artificial a lure for them. Now there is a plan to construct a full-fledged bridge over the tracks. Will this work? Nobody, of course, knows.
A similar effort was attempted in the Borajan fragment of the Bherjan-Borajan-Podumoni Wildlife Sanctuary in Assam with limited success. Canopy bridges of bamboo poles were placed in the canopy openings inside the forest. Interestingly, hoolock gibbons, capped langurs and Assamese macaques have used these canopy bridges whereas the pigtailed and rhesus macaques have never.
The feasibility of using bamboo as bridges on the long run is questionable owing to the fragile nature of the bamboo, which tends to decay over time and become a liability rather than a solution. However, it must be recognized that natural connections rather than artificial structures are more likely to be preferred by rainforest species.
The problem of roadkills is not going to go away any time soon. We need this important infrastructure for it brings with it development but we also need wildlife to be free from this threat. Our prime concern should be never to plan for roads that run through important wildlife habitats and divert the existing ones whenever possible. Even if cannot do so much, we should modify their use in certain ways, as for example, banning their use at times when roadkills are most likely. The importance of such measures for conservation and wildlife management is invaluable.