- In the upper plateau of the Palani Hills, the native shola-grassland ecosystem has been systematically disturbed since the time the British administration moved in, during the mid 1900s. The process has accelerated in the last four decades.
- Using satellite images to track land cover changes in the region and through field surveys to verify these changes, researchers found that a staggering 66 percent of the grasslands and 31 percent of shola forests have been lost in the past four decades.
- Looking at the grasslands more carefully, the study found that agriculture chomped at the grasslands from 1993 to 2003, while marauding plantations captured them between 2003 and 2014.
- The study found that in the Palani Hills, 250 square km of grasslands were lost between 1973 and 2014, bringing down the area they covered from 71 percent to 24 percent. Overall, plantations had increased 12 times while agriculture grew from 31 square km to 105 square km.
Almost smack in the centre of the Palani hill range that forms the eastern spur of the Western Ghats, lies the hill station of Kodaikanal. This once sleepy idyllic getaway now, like many others, bustles with tourists, vehicles and is overrun by indiscriminate construction.
Situated at an elevation of over 2000 meters, Kodaikanal was once surrounded by pockets of sky island sholas nestled amidst hills of rolling grasslands on rocky mountain cliffs. The upper plateaus of the Western Ghats, rising above 2000 m, serve as sky islands because they are pockets of temperate climate nestled within tropical latitudes. Thus, they support unique biodiversity.
This was until the British administration moved into the hills in the later part of the 19th century. Terming the vast grasslands as barren, the British reshaped the Palani hills by planting exotic woody trees like black wattle (Acacia mearnsii), eucalyptus and pine. The policy of planting these trees, which could be used as pulp for paper and rayon industries, continued even later with the Tamil Nadu Government’s policies.
In the last century, these foreign imports have run such a riot in the region that they have taken over the shola forests and annexed the grasslands.
A recent study by a team of researchers from the Indian National Trust for Arts and Heritage (INTACH), Kodaikanal; Indian Institute of Science Education and Research (IISER), Tirupati; Vattakanal Conservation Trust, Kodaikanal; Ashoka Trust for Research on Ecology and Environment (ATREE), Bengaluru and others examines how native vegetation in Palani hills changed spatially and over time in the last 40 years.
Using satellite images to track land cover changes in the region and through field surveys to verify these changes, the researchers found that a staggering 66 percent of the grasslands and 31 percent of shola forests have been lost in the past four decades.
Grasslands have become fragmented bits
Although the popular perception is to focus on the loss of forest, this study shines the spotlight on the high montane grasslands in the Palani hills that have taken the hardest hit. Grasslands that once spread extensively, with connections to neighbouring areas of Kurinjimala Sanctuary in Kerala and Anaimalai hills in Tamil Nadu, have been reduced to small disjointed specks.
“What used to be the major land cover type in the landscape, that is the grassland, has been reduced to very fragmented bits,” says Arundhati Das, an independent researcher and one of the authors of the study. “This has happened in a relatively short span of time of 40 years. Ecologically, that is a major change that has taken place very rapidly. This has serious implications for major ecosystem processes such as hydrological cycles, and for organisms that depend on grasslands, including people.”
The study finds that the main culprits for these losses have been the permeating plantations and the expanding agriculture. “We found that big patches of grasslands were being converted for agriculture but smaller patches were transformed into plantations,” says Milind Bunyan, a scientist at ATREE and one of the co-authors of the study.
Quantitative analysis of habitat loss
“This is probably the first long term assessment of grassland status in the Palani hills and the results are robust,” says Srinivas Vaidyanathan, a researcher with Foundation for Ecological Research and Learning, who was not part of the study.
The seeds of the study were sown when Robert Stewart and Tanya Balcar, longtime residents of Kodaikanal who have extensively surveyed and documented the Palani hills landscape and initiated the Vattakanal Conservation Trust, noticed the changes that the native vegetation was undergoing. Then back in 2014 Ian Lockwood, an educator and another longtime resident of Kodaikanal, put together a visual analysis using landsat images of these changes in a blog post that he maintains.
Taking off from this blog post, Das, Bunyan and V. V. Robin of IISER-Tirupati put together a team to assess the changes in a more scientific fashion. “To us it was very clear that something had happened in this landscape and nobody had actually studied this,” observed Bunyan.
With the agenda set, the team wanted to find out how the distribution of grasslands, forests, plantations and agriculture had changed over space and time. They were especially interested in figuring out what the driving factors were for the manner in which grasslands were being lost. And finally, how the native vegetation has been conserved in this landscape that has witnessed many historic changes.
To begin with the researchers procured landsat images for every ten years from 1973 to 2014 of the Palani hills. As the cloud cover is low and the difference between green cultivated fields and dry grasslands is stark in the drier months, the researchers collected data only for this period.
The researchers also obtained information on plantation drives carried out by the Tamil Nadu Forest Department from 1993 to 2003. And lastly, they classified the landscape into shola-grasslands, shola forest, plantations, settlements, agriculture and fallow lands and water bodies. They mapped boundaries of roads and the Kodaikanal wildlife sanctuary.
To verify these boundaries the researchers had charted, two members of the team, M. Arasumani and Danish Khan, carried out field surveys. “We surveyed 555 locations in the landscape to check if the classification is correct or not at the ground level,” said Arasumani, the lead author who is affiliated with IISER-Tirupati. “And we got an accuracy of 96 percent.”
At first it was agriculture, then plantations
Putting together data from both – the landsat classifications and their own ground-truthing surveys – the researchers found that plantations in the neighborhood were more likely to invade grasslands than if they were at a distance. They discovered many small, irregular grassland patches taken over by plantations, suggesting that natural dispersion was responsible for grassland loss.
On the other hand, large well-defined blocks of agriculture closer to roads and settlements suggested that grasslands were converted by a more skilled hand at work. However, grasslands away from roads were more likely to be planted with timber.
Analysing their data, the researchers found that 250 square km of grasslands were lost between 1973 and 2014, bringing down the area they covered from 71 percent to 24 percent. Overall, plantations had increased 12 times while agriculture grew from 31 square km to 105 square km.
Such dramatic increase in plantation and agriculture is steepest in the past two decades making them most culpable for maximum grassland loss during this time. However, disaggregating the timeline, the study found that agriculture chomped at the grasslands from 1993 to 2003, while marauding plantations captured them between 2003 and 2014.
“Irrespective of the timeframe you consider – 1973 to 2014 or 1993 to 2014 – the results show drastic decline in grasslands,” said Vaidyanathan. “This issue has been discussed in various conservation fora, but no quantitative estimates were available to understand the magnitude of change.”
The possible reason for the increase in agriculture could be the settlement of Sri Lankan repatriates under the India-Sri Lanka (then Ceylon) agreement of 1964, signed by the Indian Prime Minister Lal Bahadur Shastri and Sri Lankan Prime Minister Sirimavo Bandarnaike. Under this pact, thousands of Tamil families working in the tea estates of Sri Lanka were repatriated to India. To find sustainable employment for them the Tamil Nadu Government started the Tamil Nadu Tea Plantation Corporation (TANTEA) under the Tamil Nadu Forest Department. TANTEA established tea estates in the upper plateaus of the Western Ghats.
But the softwood and timber plantation increase could be attributed to the nationwide ban issued in 1996 on felling of green trees. Although this arrested felling of trees, new plantations continued to take root. The researcher’s estimates for these were corroborated when they cross-checked with the records of the plantation drives by the Tamil Nadu Forest Department. Such factors have rendered the native vegetation, especially grasslands vulnerable to further impacts.
Can grasslands be conserved?
To conserve the remnant grasslands and resurrect the native vegetation, the study lists out four recommendations. One, to identify and conserve grassland areas covering hillocks, streams, marshes and tucked away in plantations. Two, grasslands lightly invaded by exotics can be physically removed from multiplying further. Three, experts like Stewart and Balcar have observed that removing mature plantations makes them come back with vengeance. So, instead of the blanket felling of mature plantations, localized removal could be experimented. Four, the spread of agriculture can be checked and fallow fields can be revived into marshes.
Sky island grasslands support numerous endemic species of plants, amphibians and are the last footholds of birds like the Nilgiri pipit that depend on them. But mankind needs these life-supporting habitats too as places where rivers originate.
CITATION:
Arasumani, M., Khan, D., Das, A., Lockwood, I., Stewart, R. Kiran, R. A., Muthukumar, M., Bunyan, M., & Robin, V. V. (2018). Not seeing the grass for the trees: Timber plantations and agriculture shrink tropical montane grassland by two-thirds over four decades in the Palani Hills, a Western Ghats Sky Island. PLoS ONE, 13(1): e0190003. https://doi.org/10.1371/journal.pone.0190003.