Western Ghats: Native habitats reduced to one-third and hydrological regulation disrupted, says review article

The Western Ghats are a biologically rich region in India and one of the world’s major biodiversity hotspots. Their importance comes from exceptional variety, high endemism, and a long evolutionary history. They contain ancient plant and animal lineages alongside species that evolved more recently within the region.

The range harbours 30% of India’s plant and animal species. Many narrow-ranged species occur nowhere else. This combination makes the Western Ghats both a living record of earlier evolutionary history and an active centre of species formation.

The hotspot is also densely populated and heavily used. Plantation expansion, dams, roads, climate extremes, invasive species, urbanisation and other infrastructure have reduced native habitats to one-third of their original extent. Conservation therefore must protect biodiversity, ecological connections and evolutionary history, not only individual species.

The Western Ghats have lost most of their original native habitat. The review estimates that only one-third of the original extent remains. This means roughly two-thirds has been altered, converted or otherwise removed, leaving less space for species and weakening the ecological functions of intact landscapes.

Natural forest cover declined by an estimated 40% between 1920 and 2010. The decline was steeper in the northern Western Ghats and shallower in the southern areas. Plantation expansion, infrastructure and other land-use changes contributed to this long-term reduction.

These figures describe related but different measures. Native habitat includes natural ecosystems beyond forest, while forest cover concerns forests specifically. The remaining habitat is under further pressure from climate extremes, invasive species, urbanisation and infrastructure, making restoration and connectivity increasingly important.

Over roughly two centuries, commercial plantations, dams, roads, railways and other infrastructure changed native Western Ghats ecosystems. Plantation expansion began strongly under British colonial rule and continued afterward. Natural forests and other biodiversity-rich habitats were converted into production landscapes, reducing habitat and altering ecological connections.

Coffee began around 1860, while tea and rubber expanded in the colonial period. Today, coffee covers about 3,000 square kilometres, tea 1,134, cardamom over 730 and rubber 5,000. Rubber increased by more than 600% in 70 years. Cashew also spread across nearly 53,500 hectares in the northern region, threatening lateritic plateaus.

Dams and infrastructure added further pressure by changing water systems and dividing habitats. Roads, railways, canals and power lines cut through landscapes. The result was forest loss, fragmentation, disrupted wildlife movement and weaker ecological regulation across the region.

Hydrological regulation means the way ecosystems capture, store, filter and gradually release water. Forests, soils, streams and wetlands influence when water enters rivers, how much is retained, and how quickly it moves downstream. This matters because the Western Ghats are critical to peninsular India’s water security.

Land-use change, dams and infrastructure can alter these natural processes. Replacing native vegetation with plantations or built surfaces changes runoff and water storage. Fragmentation can also interrupt connected catchments. The review links habitat loss and development with disrupted hydrological regulation, although it does not quantify each project’s individual effect.

When regulation weakens, water availability can become less reliable and intense rainfall can produce greater flood and landslide risks. Protecting native habitats and ecological connections therefore supports both biodiversity and the water systems on which peninsular India depends.

Linear infrastructure means long, narrow developments such as roads, railways, canals and power lines. In the Western Ghats, they cut across connected habitats rather than replacing all habitat at once. This creates fragmented patches and makes movement between them more difficult for wildlife.

The region has 26,400 kilometres of roads, 10,042 kilometres of railways, 2,621 kilometres of canals and 132 kilometres of power lines. These structures interrupt ecological connectivity and wildlife movement. Animals attempting to cross transport corridors can be killed by vehicles or trains, producing wildlife mortality.

Fragmentation is especially serious for narrow-ranged endemic species because their remaining habitat is already limited. Conservation planning therefore needs to maintain connectivity among landscapes, alongside protected areas and community reserves. Without connected habitats, species may struggle to move through changing conditions or maintain viable populations.

Climate change is adding new stress to ecosystems already altered by plantations and infrastructure. Historical observations show total rainfall has declined since the 1950s, while the future direction of the monsoon remains uncertain. At the same time, global warming is increasing extreme rain events in the region.

This means a place can receive less rainfall overall but get a larger share in intense bursts. Events exceeding 900 millimetres per day or 100 millimetres per hour can trigger landslides, even in forests. Projections indicate annual maximum rainfall may rise substantially at lower elevations and more modestly at middle elevations.

Warming and rainfall anomalies are projected to be highest in the north. These changes could intensify floods, landslides and stress on species already facing habitat loss, invasive species and urbanisation. Conservation must therefore account for changing climate conditions, not only current habitat boundaries.

Endemic species live in restricted regions, so damage to their habitat can threaten their entire global range. Evolutionary lineages and phylogenetically distinctive species represent unique branches of biodiversity. Climate or evolutionary refugia are places that sheltered life through past change and may remain important for persistence.

The Western Ghats combine all these values. They are a “museum” of ancient lineages and a “cradle” of recently evolved endemic species. Many endemics have narrow ranges, so protecting only large, charismatic animals can leave irreplaceable plants, small animals and evolutionary history unprotected.

The review recommends systematic conservation planning beyond simply expanding protected areas. Plans should include community reserves, landscape connectivity, patterns of endemism, phylogenetic distinctiveness and evolutionary refugia. This broader approach can protect biodiversity’s variety, history and future resilience under climate and land-use pressure.