Why we have to be careful about losing the forest for roads

Protected forests are meant to be biodiversity repositories but all too frequently automobiles speed and trains thunder through them. Tall electric pylons, deep concrete-lined canals and pipelines carrying gas, petroleum or water carve up the forests even further. Everything from insects and amphibians to elephants get injured, maimed or killed while trying to cross these barriers.

A full forest is better than the sum of its parts. Reuters

The few estimates of road-kills may be underestimates as many injured animals drag themselves off to die in the nearby shrubbery. Some carcasses are scavenged by other animals, which also fall prey to speeding vehicles. The total number of animals being killed on roads running through parks is unknown. Despite the problem being recognized and proposals for more such projects being tabled, there are no national guidelines for the construction and maintenance of these structures in forested areas. In an effort to set this situation right, T.R. Shankar Raman of the Nature Conservation Foundation, Mysore, drafted a background paper for the National Board of Wildlife.

Of the different kinds of animals, amphibians and reptiles are the worst affected by roads. About ten years ago, a study conservatively estimated that 10,000 of them were squashed on a 100 km stretch in the Anamalai hills of the Western Ghats. Can these species withstand this level of mortality? We don’t know what proportion of the adult population is being killed to estimate whether this poses a dire threat to their conservation. However, in Europe, studies indict roads near breeding ponds as a major threat to some species of amphibians. Every year, volunteers of Froglife help thousands of toads cross roads in the UK and yet, an estimated 20 tons of the amphibians are run over. The US spends thousands of dollars building frog tunnels under highways.

Besides the danger to animal lives caused by roads, railways and electric pylons, linear structures reduce the area available to wildlife even within these safe refuges. Bandipur Tiger Reserve has 800 km of roads. With an average width of 10 metres, that’s 8 sq km of forest lost. Additionally, 30 to 40 metres of vegetation are cleared on the shoulders to allow greater visibility. So the forest area lost to roads is three to four times higher.

Any clearance allows the sun to blaze into tropical forests, causing temperature and humidity fluctuations. During storms, wind currents whip through roads, railway lines and other “wind tunnels,” snapping branches and toppling trees. The opening up of the forest heats up the ground that some sensitive plants are unable to tolerate. It is estimated that the effects of cutting through forests can extend up to 100 metres on either side of the clearing. In all, Raman reckons the 874 sq km Bandipur Tiger Reserve has lost about 80 sq km, a tenth of the area, to roads. In other words, every km of road ruins about 10 ha of forest.

That’s not all. About 2000 km of firebreaks slice the Park. With an average width of 25 metres, an additional 50 sq km of forest is gone. While it may be argued that this degradation is for the larger good of the preserve, a study in neighbouring Mudumalai Wildlife Sanctuary concluded that firebreaks are not the best defense against a conflagration. Fire-lookout camps are more effective. Raman also observes that firebreaks are hacked even through wet evergreen rainforests such as Chimmony Wildlife Sanctuary where the risk of fire is low leading to unnecessary loss of forest.

Any of these straight line clearings and structures bifurcate territories and oust animals from them. Smaller animals whose home range is cleared for the road or canal may lose their ability to survive entirely. Where there are no canopy connections above roads, primates like lion-tailed macaques are forced to dodge traffic at great risk to life and limb. Or if it is high tension electric lines that cut through the forest crown, the primates may try to use the cables as a bridge and get electrocuted.

Roads with railings can become insurmountable barriers for animals. The ones especially along hillsides are the worst. Animals are trapped between the steep slope on one side and a concrete parapet wall, the commonest form of railing, on the other. Whether they are slow moving animals like pangolins and turtles or faster ones like jackals and mouse deer, they have to trot several km before a break in the railing allows them to escape. However, many panic, run helter-skelter and get killed.

Any clearing in a forest is like an open sore, an entry point, all too readily exploited by foreign weeds, like Eupatorium and Lantana that do not allow forest plants to grow. The seasonal clearing of vegetation along the edges of roads, firebreaks, and under electric pylons, helps the weeds spread far and make inroads into the surrounding forest. Roads along hill slopes destabilize the soil causing landslides while debris from the construction is frequently dumped downhill smothering the forest below.

Raman also suggests ways of minimizing the damage caused by such engineering feats. Wherever possible, realigning the road or structure outside the forest should be considered first. Even existing roads and pathways that cause heavy damage should be realigned outside forests. This additional investment would immeasurably boost the conservation value of the forest. If more than one pathway has to be cleared, then they should all follow the same alignment rather than slicing the entire forest into many little slivers.

Where realignment is not possible, mitigation measures need to be planned right at the drawing board stage. The website of the Australian World Heritage Management Authority provides detailed guidelines for such structures. Other recommendations have also been made by the Elephant Task Force, Wildlife Trust of India and Wildlife Institute of India.

Efforts at mitigation are already underway in some parts of the country. The collaboration between Wildlife Trust of India, the Railways and the state government of Uttarakhand to prevent the death of elephants on railway lines involved several actions such as leveling steep embankments, talking to train drivers and railway staff, as well as monitoring the movement of elephants. From 20 elephants being mowed down by trains over 15 years in Rajaji National Park, there has been no death for the last nine years.

Where roads already run through parks, a complete ban on night traffic is necessary. Several nocturnal animals are blinded by the bright headlights and sit suicidally motionless in the middle of the road. Daytime travel through forest areas should have speed limits so animals have time to react and get out of the way. Better still would be to dissuade people from using the forest road by imposing a Conservation Contribution Charge.

Raman makes the case for preserving old, native, road-side trees. Their shade suppresses the growth of weeds, their roots prevent soil erosion, and their branches and trunks shelter the road from driving rain. Their canopies allow arboreal species to cross over without having to take great risks. Where there are gaps, artificial bridges can help tree-living animals commute.

The construction work force cannot be allowed to billet in forest areas and should be transported in every day. All building materials need to be sourced from outside and not excavated or harvested from the jungle. These may seem obvious but are unfortunately normal practice. It’s likely that each project may have its own peculiarities that require consideration and field visits by wildlife scientists and ecologists ought to be conducted before granting approval.

While implementing these recommendations would promote the integrity of forests, the best case scenario is to prevent such pathways from cutting across these fragile and protected ecosystems. By allowing these structures to carve up our limited forests, we are only negating our conservation investment in them. A forest is better whole than the sum of its many parts.


Published Date: Nov 27, 2011 08:47 am | Updated Date: Nov 28, 2011 05:33 pm


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