Habitat Fragmentation and Wildlife Corridors
Habitat Fragmentation and Wildlife Corridors
Habitat loss and fragmentation are the two main contributors to continuing biodiversity decline across the landscape. A holistic approach is required across both public and private lands to protect and manage natural ecosystems and ensure connectivity between remaining habitats.
- A wildlife corridor is a link of wildlife habitat, generally native vegetation, which joins two or more larger areas of similar wildlife habitat.
- Corridors can consist of
- a sequence of stepping stones across the landscape (discontinuous areas of habitat such as paddock trees, wetlands and roadside vegetation)
- continuous lineal strips of vegetation and habitat (such as riparian strips, ridge lines etc.),
- they maybe parts of a larger habitat area selected for its known or likely importance to local fauna.
There are three divisions of corridor according to their widths:
- Regional– (>500m wide); connect major ecological gradients such as migratory pathways.
- Sub-regional– (>300m wide); connect larger vegetated landscape features such as ridgelines and valley floors.
- Local– (some <50m); connect remnant patches of gullies, wetlands, ridgelines, etc.
How Habitat Fragmentation occurs?
- When native vegetation is cleared, fragmented patches or islands are created.
- These patches may become increasingly cut-off from other areas of habitat resulting in many plant and animal species becoming isolated, especially when land between the patches is permanently altered for human activities.
- As these vegetation patches are reduced in size and become increasingly isolated, the on-going viability of ecosystems and individual populations of species within them is severely affected.
- This ultimately leads to a break down in ecological processes such as species migration, dispersal, recycling of nutrients, pollination of plants and other natural functions required for ecosystem health.
- The likely result is severe biodiversity decline and local extinction of sensitive species.
Why Animals need them?
- Corridors are critical for the maintenance of ecological processes including allowing for the movement of animals and the continuation of viable populations
- By providing landscape connections between larger areas of habitat, corridors enable migration, colonisation and interbreeding of plants and animals. This allows an exchange of individuals between populations, which may help prevent the negative effects ofinbreeding and reduced genetic diversity (via genetic drift) that often occur within isolated populations.
- Corridors play an extremely important role in the maintenance of biodiversity, but they can only partly compensate for the overall habitat loss produced by the fragmentation of the natural landscape. It is important therefore, that vegetation remnants and vegetated corridors are maintained and enhanced as a network across all lands both private and public. In this way private landscapes can contribute to wider landscape conservation efforts by enhancing and linking existing reserves and conservation networks.
- Corridors may also help facilitate the re-establishment of populations that have been reduced or eliminated due to random events (such as fires or disease).
- Habitat corridors may be defenceless against a number of outside influences, but they are still an efficient way of increasing biodiversity. Strips of land aid in the movement of various animal species andpollen and seed dispersal, which is an added benefit to the intended one (M. 2002). For example, when insects carrying pollen or birds carrying seeds travel to another area, plant species effectively get transported, as well.
- Another positive aspect of corridors is that they allow both animals and humans to occupy virtually the same areas of land, and thus co-exist where without the corridor this would not be possible.
- Large animals such as bears can be attracted to residential areas in search of food due to lack of natural resources because of habitat fragmentation. A corridor would provide a passage for the bears to forage in other locations, so that they would not pose as much of a threat to humans.
A major downfall to habitat corridors is that not much information has been gathered about their success. Due to the lack of positive data, many agencies will not allow corridors to be established because they are unsure of their effectiveness. Another problem with corridors is that they are not as useful as simply preserving land so that it cannot be fragmented. However, it is becoming very difficult to set aside land for nature reserves when road-building, industry, and urban sprawl are all competing for space.
Even if corridors are sought as a solution, it does not necessarily mean that animals will use them. Especially in the case of overpasses, research shows that animals do not like to use them to get to another remnant area of land. Usually overpasses are built over busy highways, and many species are too timid to expose themselves in front of all of the traffic. As more roads and buildings arise, there becomes less space to try to preserve.
Habitat corridors need to be species-specific (not every kind of animal will use every kind of corridor) and corridors can be barriers to some species. For instance plants may use road verges as corridors however some mammals will not cross roads to reach a suitable habitat.
there is a possibility that corridors could not only aid in the dispersal of native organisms, but invasive ones, as well (Beier & Loe 1998). If invasive species take over an area they could potentially threaten another species, even to the point of extinction.
Factors affecting Tiger Corridors
- The presence of many villages in the critical tiger habitat (CTH) is creating tremendous pressure on the natural resources such as fodder, fuel wood, non-timber forest produce and timber for agriculture and house construction within the sanctuary
- Although most of the mining activities are banned inside the sanctuary, there are number of mines operating around and very close to the sanctuary. The area is rich in shale and sandstone, which is extensively mined in this part of Rajasthan. Illegal mining activities are rampant in the forests adjoining the sanctuary. There have been occasional instances and reporting of poisoning of animals from the area.
- Increasing demand for water from the surrounding human habitations is the greatest threat to the river systems. It faces severe extractive and disturbing pressures in the form of dams, water impoundment and abstraction, sand and stone mining, infrastructural development, water pollution, over-fishing, poaching, livestock grazing, riparian chemical agriculture related activities and water diversion.
- Tiger corridors are influenced by National Highways, tourism etc. which cuts across the forests. It leads to accidents and poaching.
- Tiger is a territorial animal which can’t breed in small and fragmented habitats and 80-100 tigers require an area of 1000 km2 , otherwise they would kill and maim each other in order to prove their dominance.