Forest fragmentation is the breaking of large, contiguous forested areas into smaller forest patches, separated by roads, agriculture, utility corridors or other anthropological developments.
It is a gradual process which starts with smaller, discontinuous patches in an otherwise unbroken forest or grassland. When the forests are highly fragmented, the size, integrity and connectivity of the remnants deteriorate beyond, making the area no longer an adequate home for the native plants and wildlife.
Forest fragmentation can be induced by natural causes like lava flows and other natural calamities or by man-made causes like the conversion of forest to farmland, and infrastructure development in Protected Areas. The anthropogenic fragmentation of pristine terrestrial habitats is occurring at an accelerating rate globally.
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Fragmentation affects biodiversity by decreasing the habitat, and because of the opening up of the once extant habitat, now we have changes in physical and biological properties, and the disruption of movement and dispersal patterns of the native wildlife.
Habitat destruction, defined as the elimination of the conditions necessary for animals and plants to survive, not only impacts individual species but the health of the global ecosystem.
Loss of habitat is one of the biggest ramifications of forest fragmentation. When a forest area is fragmented, the plant and animal species in that area are rendered shelter less. This could endanger many endemic species and can even lead to its extinction. This has far-reaching impacts on the planet’s ability to sustain life.
For example, if we consider the Himalayan ranges, a study by WWF shows that habitat loss is extensive in the region with - over 75% of the original habitat destroyed or degraded.
The pressures are ever increasing due to unsustainable extraction of resources and the incursion of linear infrastructure such as roads in this geologically and ecologically fragile region.
Fragmentation leads to increased light levels, higher daytime temperatures, higher wind speeds, and lower humidity. It changes and disrupts the microenvironment at the fragment edge. Species which are sensitive to these changes such as temperature and humidity can be wiped out from these fragments.
Moreover, these factors also contribute to forest fires, which is a grievous threat to biodiversity. Fire can also spread to these fragments from nearby agriculture fields or other human settlements. In this process, many species will be eliminated.
These patches also tend to be vulnerable towards invasive species, leading to altered ecosystems.
Disruption of Movement
Forest fragmentation divides a larger forest into two estranged forest patches. This would obstruct the free movement of animals from one region in the forest to another. When there is no other route for movement between landscapes the animals try to move through human-dominated landscapes which often leads to conflict with the animal getting killed, loss of life, livestock or property.
Due to lack of habitat for wildlife to move, human-wildlife conflict with tigers, leopards, elephants, wild boars and other ungulates are on the rise. From the perception of wild animals, areas of human settlement or agricultural lands are nothing but part of the larger habitat that existed in the past.
Retaining or restoring connectivity between fragmented forests is of greatest importance. Ensuring connectivity between forests and Protected Areas is what we call corridors. As mentioned earlier, loss of connectivity between forests results in human-wildlife conflict as wildlife especially long-ranging animals such as elephants and tigers come out of the forest into human-dominated landscapes that result in crop-raiding, damage to life, property and live-stock causing animosity towards wildlife on part of communities residing adjacent to the forests. Lack of connectivity also often results in local extinctions of species, inbreeding, lack of genetic diversity and non-adaptation to climate change.
These corridors provide a safe travel route for animals moving from one region int the forest to another. Thus, animals are not forced to wander into the human-settlements, thereby mitigating conflict.
Wildlife corridors may be natural or artificial. Natural corridors are usually thin strips or a series of small clumps of high-quality habitat that connect the isolated patches. Artificial corridors are generally constructed where there is a lot of human activity. 'Land bridges' or underground tunnels are artificial wildlife corridors that provide a safe way for animals to cross a road throughout the day.
Article by Gokul G K
Illustrations by Radha Pennathur
- Habitat Fragmentation and Landscape Change An Ecological and Conservation Synthesis by David Lindenmayer, Joern Fischer