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| Last Updated:: 17/10/2022

Longwood Shola forest is a water source for villages in the Nilgiris, maintains biodiversity



by Gretta on 14 October 2022, Mongabay India




  • Longwood Shola, the only urban shola forest in the Nilgiris, is a 116-hectacre forest patch interspersed with grasslands.


  • The shola forest has proven to maintain the hydrological regime of the region, capturing rainwater through marshes and releasing it via streams.


  • Home to the threatened Nilgiri marten and other rare fauna and flora, the forest patch is rich in biodiversity.




The Longwood Shola, the last and the only urban shola forest in the Nilgiris district of Tamil Nadu was recently granted the Queen’s Commonwealth Canopy (QCC) accreditation, a forest conservation programme across the commonwealth countries to conserve unique indigenous forest patches. Even before this accreditation, Longwood Shola, a reserve forest patch in the heart of the Kotagiri town in the Nilgiris has played a significant role in maintaining the biodiversity and hydrological cycle of the town.




This 116-hectare forest patch has been the drinking water source for 18 villages with 30,000 families in the town, apart from wild animals, birds and livestock, as well as a water source for agriculture, according to a study by the Nilgiris Forest Department, says Nilgiris District Forest Officer Sachin Bhosale Thukkaram. “We found that a swamp or wetland area in Longwood Shola captures water and acts as a water source downstream,” he told Mongabay-India.



Classified as ‘southern montane wet temperate forest’ in the book A Revised Survey of the Forest Types of India (P278), the sholas are found in the upper reaches of the Nilgiris, Anamalai hills, Palani hills, Kalakadu, Mundanthurai and Kanyakumari in the states of Tamil Nadu and Kerala. This is a unique system, seen at an elevation range of 1400-2700 km, where “the vast grassland is interspersed with forest made up of evergreen native trees which are dwarf in nature and hill slopes covered with native grass species.” The vegetation is a double-layered storey with a closed canopy.  Various features of shola (shola derived from Tamil solai meaning tropical rainforest) forests, such as persistent cloud cover, and moisture-capturing capabilities, make them play a critical role in hydrology and biogeochemistry.





The shola-grassland ecosystem is one of the most diverse but threatened landscapes of the Western Ghats. India has lost 30 percent of its forests in the last few decades and continues to lose 0.28 percent every year, with over 50 percent of shola forests having been lost since 1850. These ecosystems are very sensitive to climate, making them vulnerable to climate change. They have been degraded by many natural and anthropogenic pressures like land use changes to facilitate agriculture and infrastructure.




A study on tropical montane forests across the world suggests that “in addition to providing cover and reducing erosion potential, the net precipitation (the precipitation reaching the ground) in tropical montane forests is often greater than 100 percent and can even be as high as 180 percent. These high precipitation levels have been attributed to condensation of wind-driven fog on tree crowns, called fog drip.” The study goes on to say that the protection of tropical montane habitat helps hydrological regulation for downstream consumers—evident in the Western Ghats, where major rivers originating in the shola-grassland ecosystem mosaic provide hydrological services to consumers.





Like other shola forests, Longwood Shola is nestled between two hills and acts as a perched aquifer, retaining the water that flows from these two hills and letting it flow towards the slope land area, says Nilgiris-based hydrogeologist Gokul Halan. He says that generally, soil can purify water, and it also helps in controlling floods and acts as a carbon sink. Studies in the United States found that in temperate forest ecosystems, the amount of carbon stored in soils is often greater than the amount stored above ground in living and dead plant biomass. Although the relative amounts of organic carbon in plant and soil components vary by climate and region, below-ground carbon is a substantial carbon pool.





Ecologist Godwin Vasanth Bosco says that Longwood Shola is an ancient forest that has nutrient-rich soil formed over hundreds of years. “The soil is dark and has high water retention capacity. Even in case of high rainfall, the soil has the capacity to absorb that water and release it in small amounts throughout the year,” he says. He adds that this property of the soil prevents flood situations in the forest and maintains the perenniality of streams by managing water levels in them.



The ecology of the Nilgiris was “essentially a mix of grasslands and shola forests before anthropological interventions altered it,” says Bosco. Sholas and grasslands here have more than 1200 species of plants, shrubs, ferns, grass and alga types, some of which are vanishing from other parts of the world, he adds.




Longwood Shola, at the height of 1700 metres asl, has trees that can grow up to 15 metres in height, says forester A. Vivekanandan of Kotagiri Range, Nilgiri Forest Division. “In case of heavy rainfall, the trees in this area and the soil can absorb it and regulate it,” he says. Since Longwood Shola is a reserve forest, the marshes are not destroyed. “The water that comes down from the mountain will get collected in the marsh area, which helps recharge groundwater. Similarly, it fills the streams that flow into the villages,” says Vivekanandan.




The ecosystem services provided by Longwood Shola make a case for the urgent need to preserve urban forest patches across the world. In a study conducted in a sacred forest patch in Karnataka’s Shimoga district to understand the impact of conservation of isolated sacred forest patches, it was found that conserving these forests increased species richness and carbon sequestration, among other positive impacts.