C for C : Corridors for Conservation

Wildlife corridor, as NTCA defines it, is an inherent geographical linkage (through forests, river courses or other habitat attributes) which facilitate movement of tigers and other wild animals from one source area to another. Generally speaking, a corridor can be defined as

‘linear landscape elements, meant to establish/facilitate connectivity across habitats and increase survivor-ship by increasing the diversity of specific gene pools.(Varma, 2008)

 

Tiger populations across India

The Tiger population in India can be divided into three populations  viz. The Western Ghats population, The Terai arc population (spread across the Indian states of Uttarakhand, Uttar Pradesh and Bihar, and the low lying hills of Nepal) and The central Indian population (that has about 8 states majorly Madhya Pradesh and Maharashtra). The Western Ghats hold the most robust tiger population on earth. Most parks there are largely contiguous (most of the parks are connected by forested corridors) especially in Karnataka, kerala and Tamil Nadu. The best habitat for tigers is considered to be the Nilgiri biosphere reserve which pans in these three states. The Terai arc unfortunately, which is also a very good habitat for tigers, has got hampered in a big way because of fragmentation and for many other reasons. While there are some patches where you have some of the highest densities of tigers on earth like Corbett, but most of the parks are highly fragmented and they’re far from each other. The central India has very good quality tiger reserves and it extends into many states like Maharastra, M.P, Chattisgarh, parts of Gujarat and Rajasthan. Looking at the landscape, there are several protected areas but they’re all far apart. However if compared with the terai arc landscape, the corridors between these national parks are still intact. In terai arc region a lot of these corridors have been hampered because of anthropogenic reasons. The central Indian region is physically in between the terai arc and western ghats and also from the perspective of ecology of tigers, it is in between in terms of threats. 

Why corridors?  

Just like the case of human beings where if we want to go from one place to another we’ll take a road or will go for a train (railway line), meaning that we’ll follow a particular path. Similarly in the case of animals also need to travel from one place to another. But unlike in our case where we may be going toother place for say a meeting or a trip, animals need to travel from one place to another in search of basic needs like food, mate or in search for a suitable habitats (mostly in case of young animals say a tiger or a leopard) so as to stay away from stiff competition.Therefore animals will utilise some forested pathways which are corridors for wild animals, without which they can’t sustain themselves in the long run. Primarily corridors are forested areas but in some cases there might small breaks between protected areas like agricultural patch. So the corridors are sometimes mosaic of different land use types or a river/stream in between.

Why talk of corridors when there are such good protected areas with quality tiger populations?

So what happens is that tigers also disperse, taking an example of Pench National Park, say if a cub is born in pench (National Park) so what will happen when it will grow up, it will find that pench is densely populated with tigers. So this tiger is going to face a lot of competition there. It might face competition from its father or may be other tigers nearby. So this tiger will try to find a suitable territory for itself and will disperse out of the high density area. Dispersal is a one time movement, the cub may head to Kanha National Park or Melghat or anywhere, as Pench is very well connected in all four directions. So this is a natural process by which tigers disperse out; various ecological factors like competition, food etc. facilitate this dispersal. This tiger is young and inexperienced, so he wants to move out in search of a territory for himself.

NTCA has come up with some mathematical modals, which states that if a particular tiger population, if we’re calling say Kanha as a population or Pench as a population, so each population needs to have 100 individuals to maintain genetical viability in the long run. Otherwise the classic example is Sariska Tiger Reserve, which is completely isolated and there is no connectivity for a tiger to move out or in. So what will happen is that the tigers in that areas will likely to breed with close relatives that will cause genetic problems in that populations.

Coming back to the Central Indian Landscape.

Central India is probably the biggest tiger landscape in the country and has got 23 tiger reserves and some studies also estimates that there are 70 more protected areas which harbour tigers in them but these populations are very small and only 1 i.e. Pench out of these 70 protected areas will fulfill the criteria of having 100 tigers in a contiguous landscape. So none of the other populations are genetically viable on their own. They’re all dependent on corridors for the long term viability. They might survive for few years but eventually will become locally extinct. 

So to brief the above paragraphs, the parks without corridors act as isolated islands where the movement of animals are restricted (meaning there’s no immigration or emmigration) and even a single outbreak of a disease or a poaching incident can drive that particular population to go extinct. That’s why conservationists keep emphasising about corridors. The parks without corridors will become paper parks.

Some estimates say that there is enough forest in india to support 15000-20000. Because of these corridors, tigers and other mammals like elephants moved to areas where they were not found earlier. For example there was no record of elephants in Bandavgarh Tiger Reserve for more than 50 years. But because of the presence of forest patches, Elephants moved in form Odisha and parts of Jharkhand into Chhatisgarh and then moved to Madhya Pradessh and today Bandavgarh has a population of 40+ Elephants. So because there are corridors even if local extinction occurs at a protected area or a reserve, tigers can go back if there is social acceptance in that park.

So one should loose no hope on a tiger reserve even if there are very few or no tigers present in them because in future when the protection and social acceptance improves, there’s no reason why that park can’t be as good as Kanha or pench just because of the corridors.   

In central India there are 190 protected areas, 100 of them harbour tigers at the moment and 40 of them have the potential to harbour tiger and as the tiger population is increasing there are more and more records of dispersal. Like last year (2019) there was a tiger which either went from Simplipal or Palamu Tiger Reserve to Lalgadh, West Bengal where it was killed eventually.

 

Corridors in Central India   

In central India, there is still a lot of structural connectivity and and central India still harbours the maximum genetic diversity among tigers in the entire world so globally this population is very important. Central India, with the existing structural connectivity, has around 150 wildlife corridors in the central India and eastern ghat landscape, potentially allowing a tiger to walk from Maharashtra to Odisha. 

Problems With Linear Infrastructure and Corridors

Take an example of a protected forest which say almost round in shape. So if one wants to construct a road one need not to cut the forest to build the road but can bypass the road around the periphery of the forest. But since Roads and corridors both are linear in nature it’s not possible to bypass the corridor and has to cut through it in order to build a road. That brings us to the alternatives…….

Mitigation Structures 

A) Overpass :-

Which is built above the road and is mostly a feasible option in hilly terrains. Currently there are no active overpass in India.

B) Underpass :-

World's longest and India's first dedicated tiger corridor, the underpass connects two famous wildlife parks - Kanha and Penchon NH7 (44) highway that passes through the tiger dominated Kanha-Pench Corridor in Maharashtra and is the only functional example of an underpass in India at the moment which is used by many mammals like Tigers, Leopards and even Gaurs. 

C) Other options are :-

Tunnels - Road can go under the forest area like in the case of Samruddhi Mahamarg which is under-construction in Maharashtra. And other less efficient structures are spread breakers to limit the speed of vehicles.

Conclusion

There has been a large scale fragmentation of forests for the sake of mankind’s eternal hunger to acquire space without considering the ecological damage. There are thousands of pending proposals citing construction of roads, canals railway lines etc. Intervening at the right time, i.e., at the time of planning, and encouraging policy makers to mitigate their structure to avoid any damage to the corridors so that they’ve enough time to consider to doing surveys, decide the budget and the engineering plans because it’s a very complex thing getting mitigation structures onto these infrastructures and its less costly than it looks as for example the NH7 was built with a budget of 42,000 crores and the mitigation structures (9 underpasses) costed around 325 crores i.e. less than 1% of the whole project. However costs can be managed when the intervention is done at the right time and stage and the development work is completed on time because with time the costs of the materials used for the structures also increase like cost of cement, labour, steel etc.

Hope you learnt something new toady...

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Written By:-

Rajat Pandey