Western Ghats: Original habitat reduced to one-third and hydrological regulation disrupted, says review article
The Western Ghats, the world’s most densely populated biodiversity hotspot, not only harbor 30% of India’s plant and animal species, but are a ‘museum’ of ancient plant and animal lineages and a ‘cradle’ of recently evolved species endemic to the region.
Yet two centuries of plantation expansion, dams, roads and infrastructure development, now joined by climate extremes, the accelerating spread of invasive species, and urbanization and infrastructure, have reduced native habitats to one-third of their original extent, disrupted hydrological regulation critical to water security in peninsular India, and caused contractions among narrow-range endemics, a new Biodivity Review paper reports Wednesday.
“Origins, Threats and Conservation of Biodiversity in the Western Ghats” is authored by Kamaljit S. Bawa, Jagdish Krishnaswamy, Jahnavi Joshi, Ayyappan Narayanan, Kiran Mathramkot Chandrasekharan and Lokesh Bagepalli Subramanyam. from the Department of Biology, University of Massachusetts, Boston, MA, USA, School of Environment and Sustainability, Indian Institute for Human Settlements, Bengaluru, CSIR-Centre for Cellular and Molecular Biology, Hyderabad, India/Academy of Scientific and Innovative Research, Ghaziabad, India, Department of Ecology, French Institute of PoIFREIFREIFUM CNRS-MEAE, Puducherry, respectively Geo-spatial Laboratory, Indian Institute for Human Settlements, Bengaluru.
Incidentally, the review is dedicated to the late Madhav Gadgil amid a deeply divisive debate on conservation measures for the Western Ghats, including the provisions of the Gadgil and Kasturirangan Committee reports and the Centre’s latest draft notification on the proposed Ecologically Sensitive Area (ESA) in the Western Ghats.
Threats
Talking about threats to the Western Ghats, the article says that several of these pressures began during the expansion of coffee and tea plantations under British colonial rule and have continued ever since.
“Cultivation of woody cash crops is the main driver of land-use change in the region. Coffee plantations were started around 1860 and tea and rubber in the early 19th century. Coffee now occupies about 3,000 km2 and tea occupies 1,134 km² at mid-altitude, mostly in high rainfall areas, Keralana and Karta, Tamil ecosystems rich in biodiversity,” it says him. It is further reported that cardamom covers more than 730 square km at an altitude of 600 to 1,200 m above sea level, which are areas traditionally formed by natural forests. Rubber has an area of 5,000 km2, mainly in west-facing valleys, including 3,226 km2 in Kerala, with more than 600% expansion in the last 70 years. Introduced by the Portuguese, cashew has spread to nearly 53,500 ha in the northern Western Ghats alone, posing a threat to the lateritic plateaus and their ecosystems. Arecanut, once confined to the humid uplands, has now spread to irrigated drier areas, he adds.
As a result of land-use changes, the Western Ghats lost an estimated 40% of its natural forest cover between 1920 and 2010, with steeper declines in northern areas and shallower declines in southern areas, the company said.
Apart from direct land conversion, linear infrastructure is the main driver of fragmentation, the article states, pointing out that the Western Ghats has 26,400 km of roads, 10,042 km of railways, 2,621 km of canals and 132 km of power lines, which disrupt ecological connectivity and wildlife movement and cause wildlife mortality.
Climate change
It also warns of rapidly changing climate dynamics, in particular the future of the Western Ghats monsoon remains uncertain, with historical observations showing total rainfall decreasing since the 1950s, while most climate models have simulated and projected an increase in the recent past and into the future.
Despite the complexity of annual rainfall trends, which is one of the consequences of global warming, the Western Ghats are already seeing an increase in extreme rainfall events, so in areas where there has been a slight decrease in annual rainfall totals, more of the rainfall has been received as more intense rain, he says.
“Extreme rainfall (over 900 mm per day and more than 100 mm/h) in the Western Ghats can trigger landslides, even in forested areas. Some future projections suggest that annual maximum rainfall will increase substantially at lower elevations and more modestly at mid-elevation, consistent with increasing flood risks. In addition, precipitation and warming anomaly highest in the north.
The review article says that systematic conservation planning, in addition to considering the expansion of protected areas, community reserves and enabling connectivity between landscapes, must take into account patterns of endemism, phylogenetic divergence and evolutionary refugia.
“…Current conservation is disproportionately focused on charismatic megafauna and does not reflect the spatial distribution of unique evolutionary lineages or data-poor taxa,” it says. “Effective conservation requires three mutually reinforcing elements: spatial prioritization anchored in biogeographic gradients, climate-resilient management and habitat restoration, particularly for sky islands, lateritic plateaus, and freshwater ecosystems, and inclusive management of land-saving and land-sharing conservation interventions,” the study adds.