- India’s biodiversity hotspots are being increasingly fragmented by roads, dams, plantations, and urbanisation, which disrupt the complex interdependent relationships among species.
- This fragmentation leads to reduced habitat areas, increased isolation, and adverse ecological impacts, including declines in species that require large, undisturbed habitats.
- Experts emphasise the need for improved implementation of existing policies, enhanced zoning regulations, and landscape-scale conservation strategies and species-oriented conservation plans, to mitigate these impacts and protect biodiversity.
Imagine a continuous, thick forest with centuries-old trees, endemic plants, animals, birds and insects that you can’t find anywhere in the world. The relationship between these species is complex and they depend on each other to survive and thrive. Now, envision this forest being sliced into pieces by roads, dams, plantations, infrastructure and energy projects and expanding villages and towns.
In a rapidly urbanising India, once-pristine habitats are increasingly fragmented by unsustainable natural resource management decisions. Some anthropogenic activities disrupt the ecological balance of ecosystems in more ways than we understand. Some studies around the world single out ‘fragmentation’ as the most important factor in the decline of biodiversity.
India hosts significant parts of four global biodiversity hotspots out of the 36 identified, within the Western Ghats; the Andaman and Nicobar Islands; the western Himalayas; and the eastern Himalayas. While patches of them are legally protected, much of these regions have turned into mosaics of native habitat peppered with anthropogenic landuse changes.
How did the hotspots start fragmenting?
The fragmenting or breaking up of habitats leaves a more complex web of consequences compared to a total loss, as in the case of deforestation. A 2003 study on habitat fragmentation observes four major signs of fragmentation – a reduction in habitat area, an increase in the number of habitat patches, a decrease in the size of these patches and an increase in the degree of their isolation.
“Studies looking at historical maps and satellite imagery have shown that much of fragmentation in the Western Ghats occurred in the 20th century, largely due to the expansion of commodity crops,” says Anand M. Osuri, a scientist working with Nature Conservation Foundation’s (NCF) Western Ghats programme. “The southern ranges of the Ghats such as the Nilgiris, Anamalais and Coorg were among the first to be transformed for crops such as tea and coffee, while cashew and rubber have expanded more recently in the northern Western Ghats.”
Divya Vasudev, an ecologist with Conservation Initiatives, a non-profit based in Guwahati, has worked extensively in Assam, Meghalaya and Nagaland. Her work has focused on connectivity and landscape-scale conservation, which are closely tied to fragmentation. She reveals a history similar to that of the Western Ghats. “The Brahmaputra floodplains have seen forest loss and fragmentation in the past due to large-scale tea expansion and agriculture. There is still high forest cover, but this is being lost to and fragmented by monoculture plantations and other reasons. In Garo hills, for instance, there is extensive arecanut plantation, and in some places, rubber. In the Khasi hills, broomgrass plantations are expanding,” she says. Vasudev adds that oil palm remains a threat, though it is not extensive in places where she works, which may not be ideal for its growth. Such monoculture plantations tend to exist alongside patches of fragmented forests and settlements, creating a mosaic landscape.
In more recent times, various forms of urbanisation drive fragmentation – hydroelectric and irrigation projects, mines, roads, railways and so on. Development of roads and settlements is varied and can be more of a threat in some areas as compared to others. “The highway running south of Kaziranga National Park blocks the connectivity of animals, especially in this current flooding season, and the department puts in a lot of effort to ensure animals can cross,” Vasudev adds. Jaintia Hills, Meghalaya, a mineral-rich region that is acutely exploited for mining, also has observed an increasing number of patches.
A study in the northwestern Himalayas ran satellite data from Ranikhet forest range in Uttarakhand (1976 to 2013) through a geospatial mapping tool. Here too, cropland, fallow land and urban settlements grew the most in the previous century, from 1976 to 1990. The area of perforated (having small clearings) forests increased throughout the period. Core areas grew smaller – those under 100 hectares tripled and those over 100 hectares nearly halved.
A country-wide study by Centre for Wildlife Studies (CWS) India, found this happening everywhere, especially due to high tension power transmission lines and roads. In fact, it found the presence of some kind of linear infrastructure through 70% of protected areas assessed.
Read more: A toolkit to identify high conservation-value areas
What happens to biodiversity in a fragmented ecosystem?
Experts note a lower probability of species presence in fragmented habitats in the northeast. “Some of the more vulnerable species are only found in low disturbance, larger, good quality forests. Hoolock gibbon, India’s only wild ape, needs a closed canopy for survival. Other large-bodied species such as gaur and sambar are also found more in intact forests,” says Vasudev. Similarly, she notes that species with a lower dispersal capacity may be sensitive to forest quality (preferring thicker forests), like the pale-chinned flycatcher.
Osuri echoes a similar sentiment, sharing the example of a study performed by his team on bird communities in the coffee estates of Chikmagalur. Estates that were closer to patches of native forest hosted higher biodiversity than those that were not. Pockets of remnant forests interspersed with coffee had a positive impact on birds, especially those that were range-restricted or highly threatened. However, they held no comparison to an unfragmented forest.
“We found that forest specialist species – that is, tree species characteristic of undisturbed rainforests – went missing from forest fragments,” he says. According to him, these included many long-lived species that grew large, sported dense wood, and offered large seeds dispersed by large animals such as primates and hornbills. Fragments, on the other hand, mainly had smaller tree species with lower wood density that were dispersed by wind or smaller animals.
The value of small patches shouldn’t be discounted all the same. “Some species, which one may consider as specialists, even gibbons, are sometimes seen in small fragments,” says Vasudev.
In the higher altitudes of the western Himalayas, wide-ranging, naturally restricted species such as the snow leopard, feel the impacts of fragmentation quite harshly. Snow leopards tend to need up to 200 sq. km. per individual, and also do not venture far below the peaks of mountains. Many areas have high altitudinal gradients, like the peaks in Jammu and Kashmir that fall into low valleys. “Around Kishtwar National Park, there are huge dams being built on the Chenab river, and this can limit the accessibility of the snow leopards who don’t venture to the valleys, only using the upper limits,” says Munib Khanyari, who is a researcher of NCF’s High Altitudes programme. Infrastructure, coupled with fast melting glaciers, are rapidly reducing the range of the snow leopard. When the ecosystem loses this apex predator, it can potentially lead to a sudden increase in meso-predator populations, according to Khanyari. “The meso-predators of this landscape are the red fox, Himalayan stoat, and a few species of weasels like the pale weasel, among others.”
Fragmentation in the Andaman and Nicobar archipelago looks different from the mainland. The marine ecosystem naturally offers better connectivity. However, Vardhan Patankar, a conservationist at GVI, an organisation that curates biodiversity conservation programmes, who spent years monitoring corals in the islands, explains that terrestrial fragmentation on the islands themselves impacts the seas. “Fragmentation on the islands coupled with extreme weather events such as heavy rainfall, leads to a much higher run off of sedimentation into coastal marine waters,” he explains.
“Additional run off from the land to the ocean leads to changes in the ocean chemistry, like pH level. This affects variety of marine animals including crustaceans and mollusc, whose calcium carbonate structures decompose faster. Excess sedimentation also chokes corals, whose mucus layers can filter out only moderate levels of sediments,” he adds.
How does invasive flora impact fragmentation?
Another persistent issue in our natural spaces, invasive flora, often gains an advantage from drivers of fragmentation such roads and other linear infrastructure.
“Invasive alien plant species such as Lantana camara, which do well in open and disturbed conditions, easily colonise and proliferate along the edges of forest fragments,” explains Osuri. In such cases, the weed outcompetes and suppresses the growth of native tree saplings. Removing the invasives and re-establishing native canopy cover may help keep them at bay, he suggests.
Coffee, in some parts, is turning invasive too, even deep in the forests in the Western Ghats. When this shade-loving crop is eaten by monkeys and civets, the animals pollinate the seeds as they move from farms to forest spaces, where they can thrive in the understory.
Edges of fragments are also areas where soil health deteriorates drastically, as found in several studies. Temperatures of the soil are higher, thus making them drier. Nutrient cycling and litter decomposition rates are known to decline along edges. One such study of soil health along fragment edges in shola grasslands found that soil temperatures decreased as distance from the edge increased.
Edges also release more carbon. Osuri points to studies that reveal forest edges with fewer large, hardwood trees storing less carbon than intact forests. Carbon is also released more rapidly into the atmosphere as more trees are felled along exposed edges.
Tourism can have unexpected effects on hotspots too. In the Andaman Islands, when the influx of tourism began shooting up a few decades ago, the Indian bullfrog arrived along with tourists. Ever since, it has turned into an invasive fauna, feeding on native amphibians. Conservationists say that the Great Nicobar Island Development Project, which aims to build a mega port, city, airport and other infrastructure, is expected to have cascading effect of sedimentation as Patankar pointed out being just one example.
Read more: Ain’t no mountain high enough: alien invasive plants increasing in higher elevations
How can we combat fragmentation?
Law and policy measures are already in place. Experts say that the implementation must improve. Patankar explains how communities understand this in some ways in the Andaman archipelago, where compliance can sometimes look like superstitions or taboos which prevent fishing at certain times of the year when species are breeding. There are about 105 protected areas in the islands, some of which are being denotified to pave the way for megaprojects.
Renu Suyal, a senior researcher at CEDAR Himalaya, points to several gaps in the western Himalayas as well. “Current policies often fall short in addressing unique ecological disruptions effectively. For instance, road expansion projects frequently lead to habitat fragmentation, disrupting wildlife corridors and breaking large habitat areas into small, isolated patches. These small populations lose genetic diversity and face an increased risk of local extinction,” explains Suyal.
Additionally, roads create noise and vibrations that interfere with the ability of reptiles, birds, and mammals to communicate, detect prey, or avoid predators. According to Suyal, Environmental Impact Assessments or EIAs often lack comprehensive measures to mitigate these impacts. Furthermore, forested areas are increasingly converted for urban and agricultural use due to inadequate zoning regulations and enforcement mechanisms.
She adds, “Currently, there is no specific, overarching policy dedicated solely to addressing habitat fragmentation in the western Himalayas. A region-specific policy would be highly beneficial.” Suyal highlights the example of the Rajaji-Corbett ecosystem, where roads and settlements have led to fragmentation. She points to some gaps: “There is a lack of stringent zoning regulations that delineate protected areas and buffer zones around national parks. Roads and highways passing through or near these parks also often lack wildlife crossings or other mitigation measures.”
In the Brahmaputra floodplains, securing remnant forests, which may be reserved forests or protected forests, is critical, shares Vasudev. In places where land and forests are largely community managed, for instance in Nagaland or Meghalaya, conservation efforts need to be supported and incentivised. “Government intervention in the case of illegal activities can also help, as seen in the Supreme Court ruling against mining in Kaziranga National Park.”
Osuri makes a similar point for the Western Ghats. All monoculture plantations may not be restored to their original native habitat, but functional connectivity through these areas can be improved.
However, Khanyari opines that conservation action in general tends to focus on small sites. “There was initially a lot of focus on small, individual sites that may not even cover the range of one or two snow leopards,” he says. “For example, some forest departments focus their work on districts, when in reality, many species like the snow leopard move across districts, states and even country borders. Government structures and policy measures need to address this for more species, similar to what is being done for tiger and elephant corridors.”
When it comes to the higher altitudes of the western Himalaya, Khanyari observes a positive trend in recent management, which is moving towards coordinated action for larger landscapes. As the drivers of fragmentation warp these hotspots, experts highlight the need for protecting the habitat and the biodiversity that are interconnected.
Banner image: Roads contribute to the fragmentation of tiger habitat in the Sahyadris. Image by A. J. T. Johnsingh, WWF-India and NCF via Wikimedia Commons (CC BY-SA 4.0).
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