Wildlife Corridors are strips of protected habitats linking larger protected areas, constructed to facilitate uninterrupted movement of wild animals, birds ,amphibians and reptiles between larger protected areas.
These wildlife areas are designed to keep native animal species from encroaching human populations in areas of high interaction between the two. They also keep animals out of harm’s way on freeways, highways and other places where their movement patterns intersect with man-made areas.
Why do we need wildlife corridors?
Wildlife corridors are often used as key conservation tools, as they allow movement between habitat patches. These connectivity paths can facilitate human wildlife coexistence as they provide safe access to required resources by reducing interactions between people and wildlife.
To understand the importance of these corridors, one must fully grasp, the threat of habitat fragmentation and habitat loss.
Habitat fragmentation occurs when large patches of land used by wildlife, is split into smaller patches due to urbanization.
Effects of habitat fragmentation
Most threatened species on the planet are being affected by habitat fragmentation. (World Conservation Monitoring Centre,1992). Habitat fragmentation involves two processes, a reduction in total habitat area and creation of separate isolated patches from a large continuous distribution, causing a reduced connectivity within populations.
Landscape species such as the Indian tiger and the American grizzly bear are among the first to disappear in fragmented landscapes. They are often found only in the largest natural protected areas, such as national parks. Without corridors, these populations are isolated and prone to random events such as virus spread, starvation, forest fires and interspecies encounters.
The influence of man-made objects on animal movement is a major focus of movement-based of landscape connectivity. Facilities such as highways reduce communication by restricting movement due to avoidance behavior and also increase the number of deaths from vehicle accidents when animals cross roads.
For example, in coastal southern California, intensive development over the past century has fragmented the landscape and has helped create a‘‘hotspot’’ of endangerment and extinction in the region (Myers 1990).
Roadways influence the movement of reptiles such as snakes, salamanders, lizards etc. Snakes can hear through their jaws and can perceive vibrations from cars passing 50 m away. These vibrations may confuse the snake and cause it to avoid the area within 50 m of a road.
Roads also divide large habitats into separate regions, isolating different animal populations, reducing genetic diversity, increasing the chance of extinction. Poachers find the forest easily accessible for illegal trade once roads are developed.
Studies indicate, cars collide with large animals over 1 million times per year in the U.S., costing over $8 billion in repairs and injuries.
Why do animals move and why landscape connectivity is necessary?
Taylor et al. (1993) defined landscape connectivity as ‘‘the degree to which the landscape facilitates or impedes movement among resource patches.’’
The reasons for movement of animals, birds or reptiles from one habitat to another are:
- Food: Scarcity of food, prey population forces species to migrate.
- Climate change: As animal and plant ranges shift in a changing climate, species and populations will need to be able to relocate over the span of years and decades. Those unable to move may die out.
- Breeding
- In search of partner: In case of small populations, species need to migrate to a neighbouring habitat for mating.
- Escape natural disasters such as diseases, forest fires, severe drought.
When environmental changes are large, usually the only options are to evolve or become extinct. Genetic diversity is required for species to evolve. Inbreeding can lead to extinction.
Thus, migration is the key behavioral adaptation that allows certain animals, birds and reptiles to thrive.
For example, each male tiger requires 20-30 sq. miles to mate, hunt and roam. A male tiger in Kanha National Park, India can migrate and mate with a female from nearby Pench Tiger Reserve or Melghat tiger reserve. They can also migrate to Satpura tiger reserve or Bor Wildlife Sanctuary. This movement facilitates genetic dispersal, keeping the genetic pool of all five tiger reserves healthy. Connectivity can also prevent human tiger conflict as it reduces tiger movement in urban landscapes.
Are wildlife corridors effective?
The success of a corridor depends upon available land, cost effectiveness, behavior of wildlife, local political involvement and wildlife friendly design. When suitable habitat is scarce, corridors are pushed into marginal areas. Managers should focus on studying animal behavior ,encouraging dispersal and migrating wildlife to utilize these corridors. Worse, it was studied that many poachers use eco corridors for camping wherever there is no proper law enforcement.The opening of the Kuthiran twin tunnels has inadvertently opened doors for human-wild elephant conflict in Kerala, India. The heavy traffic prevented the elephants from crossing the road to the Machad Mountains, but with the traffic being diverted through the tunnel, a new elephant corridor was formed in Kuthiran.
However, the question was, Will the elephants stick to the corridor? Will they get distracted and enter the farms?Recently, many villagers complained regarding this movement of elephants, who are now viewed as crop raiding menaces.
Globally, elephant-movement behaviour is influenced by environmental factors such as water and foraging availability (Boettiger et al., 2011), and rainfall (Thouless, 1996). Additionally, elephants are increasingly affected by humans and their development into previously protected wildlife areas. Wildlife managers need to focus on elephant behaviour and the pattern of their movements to successfully mitigate this conflict.
One being that elephants tend to enter agricultural and urban settlements at night to reduce their chances of coming into contact with people. The presence of villages in the corridors and increased tourism around Jim Corbet Tiger Reserve (CTR), India resulted in limitations to free movement of tigers between CTR and Ramnagar Forest Division. Therefore, it was suggested to relocate Sunderkhal village, located in a crucial spot in the corridor.
But are village relocations always the solution?
However, not all relocations are successful. An eviction drive as a result of an order passed by Gauhati High Court in 2015, to evict people living in and around Kaziranga within a month, turned into a violent clash between police and villagers and killed two people. The proposed overpass and underpass project at Kaziranga has each flyover being 6 metres high with distance of 45 meters between columns, to accommodate the movement of elephants. The building is fitted with sidewalls to reduce glare from headlights and trees are planted to protect against noise.
While the flyovers will have a cycle track, enabling farmers and workers to commute, however those who don’t know cycling will have to walk the distance which is not being welcomed by some villagers. Road widening has killed endangered species in the Annamalai Mountains and Valparai Plateau in southern India. Measures have been proposed to local authorities to create wildlife -friendly roads. This includes installing speed breakers, maintaining roadside vegetation and tree canopies, using fences and leaving gaps in the sidewalls of hill roads to allow small animals to cross the road safely.
A review of literature by Haddad et al demonstrated that evidence shown by many studies point towards positive corridors effect on animals and plant populations. However, the evidence remains weak because of confounding effects and because some species performed more poorly in patches connected by corridors than others. There have been only a few successful studies of movement, gene flow, or population sizes. Long term studies are necessary to understand the effects of corridors on wild populations.
How can the efficacy of wildlife corridors be improved?
In the near future, due to exponential growth of human population, there may be rise in developmental projects leading to increase in human- wildlife conflicts. This issue needs to be addressed and planned accordingly.
The Trans-Amazonian Highway, built in 1972, runs through the Amazon rainforest had caused deforestation on massive scale.The Peruvian government has proposed extensions to the nation’s Transoceanic highway that would cut through Manú National Park, described by UNESCO as having biodiversity that “exceeds that of any other place on earth”
The design of flyovers and underpasses must match the way animals experience and navigate the landscape. Ecologists, architects and engineers should collaborate to design structures that mimic animal environments.
Eco-Link@BKE
One such amazing example is Eco-Link@BKE, an ecological corridor,built in 2013 to connect the Bukit Timah Nature Reserve with the Central Catchment Nature Reserve. It is the first overpass in Southeast Asia built specifically for wildlife, with an expenditure of $12.3 million. Since its completion, it has been used by the critically endangered Sunda pangolins, common palm civets, slender squirrels, glossy horseshoe bats and emerald doves.
Christmas Island rangers have built a 16-foot-tall plastic bridge to guide red crabs across busy streets to facilitate their mating.
The Role of Technology
Technology can be used to predict behavior of wildlife and their movements. Paul Beier et al, used simulation models to predict minimum areas and levels of immigration needed for population of mountain lions in Santa Ana, California to become extinct.
Advances in wildlife telemetry technology have enabled collection of very accurate and frequent location data for individual animals.
Cushman & Lewis (2010) used satellite telemetry data to show that American black bears (Ursus americanus) choose movement paths that avoid roads and human residences and concentrate activity in forested areas at middle elevations.
Reproduced from WWF – Human Wildlife conflict manual
Elephant movements need to be considered in future landuse development plans, if they are not, then humans and elephants will be forced into closer contact with one another, which will result in increased negative interactions
Conclusion
Whenever there’s a road construction project in an eco-sensitive area, the government should plan for the inclusion of a wildlife structure. This could be reducing vehicular load, decreasing highway encroachment on wildlife and restoring space for animals to roam freely.
With the increased uptake and use of wildlife corridors all over the world, begs the question how much surrounding human pressure can wildlife handle to continue using the corridors and how do we factor this into our future wildlife management plans.
Understanding how wildlife adapts to increased human pressures associated with urban and agricultural expansion is fundamental to all kinds of future conservation planning.
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Written by: Dr. Nupur Sawant