An Uphill Task

In India’s Nilgiri Mountains, ecologists are working against time to undo colonial forestry practices that have damaged this unique landscape.

FROM THE TOP OF A HILL just a short drive outside Ooty, a small city nestled in southwest India’s Nilgiri Mountains, grassland washes over the landscape like a spilled can of emerald paint. It pools around clusters of stunted, broccoli-like evergreen trees known as “shola” forests with which it has struck an ecological balance that has lasted for more than 20,000 years. The landscape’s bright and inky greens seem to pop even more against August’s relentless gray monsoon rains, as though the grasses and trees know they have to try a bit harder to splash color across the rolling ground.

It is impossible for an untrained eye to discern in the middle of a downpour, but the Nilgiri Mountains contain a unique variety of life. More than 3,000 flowering plants make their home in the region, including a shrub called neelakurinji (Strobilanthes kunthiana) that blooms every dozen years, bathing the hillsides in bluish purple. According to some accounts, these mountains are named after the flower: Nil = blue, giri = mountain. More than 500 species of birds sing in these hills, flying alongside about 300 types of butterflies. Leopards and tigers slink around trunks of the evergreen sholas, while the few remaining lion-tailed macaques ruffle the canopies above. The goat-like endangered Nilgiri tahr trot through the open grasslands, unaware that soon they may not have much open space left to roam.

WITH PEAKS AND PLATEAUS ranging from 1,700 to 2,600 meters above sea level, the Nilgiri massif, which connects the two mountain ranges on either side of the Indian peninsula — the Western Ghats and the Eastern Ghats — is among the highest mountains in southern India. Over 5,000 square kilometers of the Nilgiris and its surrounding environments were declared a UNESCO Biosphere Reserve in 1986. Several Indigenous communities call the region home.

As the Nilgiris have lost grasslands, they have also lost animals that depend on this unique habitat, including the endangered Nilgiri tahr. Photo by Krishanu Seal.
As the Nilgiris have lost grasslands, they have also lost animals that depend on this unique habitat, including the endangered Nilgiri tahr. Photo by Krishanu Seal.

The plateau’s high altitude limits tree growth, making the native grassland-shola mosaic possible. Typically, these shola forest clusters have an overstory of small trees, including a variety of threatened and endangered species endemic to the Western Ghats, such as kattu shanbagam (Magnolia nilagirica), and kaatu karruwa (Cinnamomum wightii). The understory is frequently thick with endemic mosses, shrubs, and ferns, several of which are also endangered, such as the shrub Strobilanthes lanata. Grasses such as Andropogon polyptychus and Eriochrysis rangacharii spring from the open terrain that washes around the sholas, and their existence, too, is in peril.

When British foresters first came upon these ancient grasslands in the 1800s, they mistakenly believed Indigenous communities had destroyed what were once forests by burning, logging, and buffalo-grazing. They spent a century trying to “reforest” the area with exotic tree species such as eucalyptus, pine, and acacia (black wattle) that they hoped to use for timber. The colonists also set up vast tea bush plantations on the higher slopes of the mountains. After independence, the government of India continued with commercial tree-planting, adding more acres of eucalyptus, acacia, and pine. These non-native trees have since flourished, conquering a huge amount of grassland in the Nilgiris and similar nearby ecosystems — 23 percent just from 1973 to 2017, according to a 2019 study published in Biological Conservation — endangering what little grass remains in this mosaic of montane forest and open terrain. Invasive trees now threaten many endemic plants and animals that rely on these grasslands. They’re also eroding a watershed that feeds several South Indian rivers, including the Kaveri, on which millions in Bengaluru, Mysuru, Chennai, and other cities rely for drinking water, and on which farmers depend for irrigation.

In the Nilgiris, acacia has proven especially voracious, and is likely to become more so. According to a study by three ecologists from the Bengaluru-based National Centre for Biological Sciences that was published in the Journal of Ecology last year, acacia is poised to sprout even faster as the world warms.

This ecological threat at the intersection of climate change and lingering colonial ineptitude is just one such danger that could take a huge toll on India’s ecosystems as temperatures climb. Non-native shrubs like scotch broom (Cytisus scoparius) and lantana (Lantana camara) — a flowering shrub the British brought to India in 1807 — have grown so thick in parts of South India’s montane grasslands and woodland savannas, respectively, that they choke off space for animals to move. Lantana, in fact, has already begun to creep as far north as the warming Himalayas.

In the Nilgiris, foresters and ecologists have tried to rebalance the landscape for decades, but conflicting ideas about how this should be done, and the complexities of the ecosystem itself, have hampered much of the effort. Atul Joshi, coauthor of the Journal of Ecology paper, says there’s still no clear way to control acacia. One of the only things that’s certain — as another of the paper’s coauthors, Jayashree Ratnam, says — is that beating back these trees won’t be enough.

“We know grassland restoration is not as simple as removing the invaders,” she says.

BEYOND THE MARBLED ARCH that marks the entrance to the National Centre for Biological Sciences campus, one comes upon what appears to be a forest left to run wild in the city. The trees are tall and thick enough that a visitor might be forgiven for squinting at Google Maps while driving up, thinking maybe he had accidentally tapped in the address of a park.

Behind those trees, in an open-air cafeteria, ecologists Ratnam and Joshi sit sipping coffee with their study coauthor, Mahesh Sankaran, on a late July afternoon. Joshi and Sankaran speak softly, and Ratnam often takes long pauses before responding to a question, silences that suggest she’s wary of making the science seem simple.

Grasslands restoration is much more complex than bringing back a crop of trees.

Grassland temperatures in the Nilgiris often drop much lower than in the region’s forests, according to their Journal of Ecology study. Frigid temperatures kill off tree seedlings and stop them from taking hold in grasslands, sustaining the tropical montane ecosystem of the Nilgiri plateau. Acacia, they tell me, has upset this balance because it doesn’t mind the cold as much as native trees. Now, it’s also poised to spread more quickly in the warmer years to come. The ecologists studied how invasive acacia took root in artificially warmed plots of land and saw its survival rate soar close to 100 percent.

The jump in acacia survival rates is an existential threat to a traditional livelihood of the Toda, an Indigenous community whose people have long grazed buffalo on the Nilgiri grasslands. As open space shrinks, they’ve abandoned the practice in favor of growing vegetables such as carrots and potatoes, and have found work in local tea plantations.

Shriveling grassland is also squeezing animals whose lives are intimately tied to it, such as the Nilgiri pipits — little golden-brown birds with dark streaks at the crown, which eat grass seeds and build cup-like nests on open ground — and the endemic Nilgiri tahr; only about 100 of these endangered ungulates remain in the region that gives them their name. Though roughly 1,900 Nilgiri tahrs live elsewhere in South India, the species may go locally extinct as invasive trees push into grassland on which they graze. “It doesn’t have any place to go,” Joshi says.

Non-native trees have also warped the water table. Eucalyptus sucks huge amounts of water from the ground, and according to the initial results of separate research conducted in part by Jagdish Krishnaswamy, an ecohydrologist studying the region, acacia is “definitely depressing the dry season streamflow in the Nilgiris.” This affects any animal looking to quench its thirst, and Krishnaswamy says it lowers the level of water in local streams and rivers, squeezing fish into tighter spaces.

The combination of sun, heat, eucalyptus, and acacia can also drain reservoirs that sustain local and downstream residents through the dry months, leaving them worryingly low. “We believe that exotics have significantly reduced the total amount of water that is discharged into our streams,” Ravinder Singh Bhalla, an ecologist with the Tamil Nadu-based Foundation for Ecological Research, Advocacy, and Learning who is also studying the hydrology of the Nilgiris, wrote in an email. “This has obvious effects on how much water is available for human consumption, including power generation.”

In wet months, too, acacia causes problems that native trees don’t. Initial results of research Bhalla and others are working on shows that acacia soak up less water than native shola trees during brutal downpours like the one the Nilgiris saw in August, which are likely to become more frequent as the area heats up. By retaining more rainwater during a downpour and releasing it slowly, shola forests keep the surrounding soil moist and ensure a more prolonged stream of supply to local waterbodies. By absorbing less water and releasing it faster, acacia allows precious freshwater little time to percolate into local watersheds before making its way down the mountains and out to sea. Drier watersheds mean smaller streams for rivers such as the Kaveri, which supplies water to farmers across South India and drinking water to millions of people in Bengaluru and Chennai, cities that are increasingly suffering from acute water shortages during the dry season every year.

RAIN RATTLES OFF THE ROOF of the Nilgiris South district forest office in Ooty like a stream of trucks rumbling over a metal grate. People darting from buildings to cars are immediately soaked. Just outside the front door of the office, a puddle is swelling into a lake. The office has an open layout, pale green walls, and wooden desks weighed down by tall stacks of paper stuffed into crinkled manila folders. The district forest officer for Nilgiris South, Guruswamy Dabbala, mustachioed and soft-spoken, has only been in charge here for four months. He says the forest department will probably ship him off to an unknown destination in another four. That leaves him just enough time to simply continue with the acacia-clearing that the department has practiced since the 1970s, and no opportunity to test or implement any new landscape restoration programs.

Government foresters focus on a few acacia-overrun zones at a time on state-owned land in the Nilgiris, and treat the trees like an army would treat enemy soldiers. The department cuts them down, then stamps out any new acacia in these parts for two years, while attempting to establish native grasslands in its place. When asked if these efforts had helped eliminate acacia from those patches, Dabbala grimaces and shakes his head.

“When I go to the field, I can see it is again coming up,” he says.

That’s probably because the foresters’ plan is incomplete. Ripping out acacia is a start, but Dabbala says they don’t go after the plant’s seedbeds or try to establish a blend of native grasses hearty enough to outcompete the acacia.

Government attempts to replant shola forests have also failed because foresters lacked basic knowledge about the ecosystem they were trying to revitalize. According to Godwin Vasanth Bosco, a Nilgiris restoration expert and founder of the ecosystem revitalization group Upstream Ecology, foresters tried to plant shola trees in areas that had long been grassland, where the already-established grasses gave trees little chance to survive. Bosco —author of Voice of Sentient Highland, a book on the Nilgiris’ ecology — says he has propagated around 4,000 shola trees, though various factors including frost and prolonged dryness make it hard for these natives to thrive. For both him and the government, grassland restoration is a greater priority than shola reforestation in the Nilgiris.

Ecologists have tried to reorient the government’s acacia-tackling policies for years, but it’s hard to establish new practices when district forest officers are always rotating. “Anyone trying to work in grassland restoration is going to have to work with the forest department, and it depends on if the authorities are friendly or not,” says Bob Stewart, a grassland restoration expert who has worked in the Nilgiris for years. “They’re not really used to working with grasses. They’re all tree people.”

Grassland restoration is much more complex than bringing back a crop of trees, say Stewart and Bosco. First, it requires a lot more plants. Bosco says he uses 5,000 to 8,000 plants per acre of grassland, whereas five acres of forest would require maybe half that many trees. Nilgiri grasslands also contain roughly 110 types of grass, according to Bosco, whereas shola forests comprise around 90 species of trees.

“To try and recreate the complexity of grassland is almost impossible from scratch,” Stewart says. Doing so might not be much use in the Nilgiris either, given that the region’s combination of native grasses has done little to stifle the creep of acacia. Still, there are several hardier grass species that can outcompete acacia, and Bosco believes he’s come up with a mix of native grasses that might be able to hold off their much taller adversaries. These grasses are big, by grass standards, and their roots take up a lot of space, crowding out acacia seedlings.

Years of restoration attempts on privately owned land in the Nilgiris have shown that beating back acacia is possible with, as Stewart says, “a lot of labor” and time. Restorationists start by ripping out acacia from a patch of ground, plucking the tree’s seedlings, and replacing them with native grasses, a strategy Bosco echoed. Then come years of visiting the site several times a week to collect any new acacia seeds that have found their way to the designated plot, though Bosco said the amount of landscape intervention after the initial acacia-clearing “does taper down drastically over the years.” By year six, Stewart found that the restored patch needed to be checked only once a week to make sure the invasive tree wasn’t sprouting fresh roots.

Of course, six years is about three times longer than the forest department ever spends on physically maintaining the roughly 9 percent of the Nilgiris that is state-owned — yet another gap between policy and what science shows is necessary to eliminate acacia and clear space for grassland.

Years of grassland restoration efforts on privately owned land in the Nilgiris have shown that beating back invasive trees like acacia is possible. Photo by Arjun Cheyyur.
Years of grassland restoration efforts on privately owned land in the Nilgiris have shown that beating back invasive trees like acacia is possible. Photo by Arjun Cheyyur.

Frustrated by these bureaucratic inefficiencies, Bosco spent years working independently, but started advising the forest department last year through a court-appointed team tasked with halting the spread of invasive species in the Nilgiris. (Tamil Nadu’s high court set up the expert team to advise the state on how to tackle invasive species in the Western Ghats in January 2019 following a series of lawsuits by environmental groups seeking to restrain the cultivation of eucalyptus and acacia for commercial purposes.) Bosco now plans to work with foresters on a 20-year effort to remove acacia and eucalyptus from the Nilgiris and the nearby Palani Hills, and replace these trees with grasslands and shola forests. The project will be undertaken in phases, roughly 250 acres at a time. “This scale and this type of work hasn’t been done,” Bosco says.

Nobody can guarantee that this plan will work. More than 20 district forest officers could rotate through the Nilgiris over the next two decades, and there will certainly be some who are less dedicated to the project than others. Governments will flip back and forth every election season, and so will the projects those governments believe are important. Even if the work remains a priority, over the past half century, much of the Nilgiris has morphed into a fundamentally different ecosystem. Even with dedicated restoration efforts in the coming years, it is unlikely that this landscape will ever return to its pre-colonial state.

Still, looking out over the rivers of grass that even now seem to run endlessly around islands of bunched shola forest, it’s clear that this kind of public-private partnership is vital to the survival of not just the Nilgiris, but all threatened landscapes. Fusing the expertise of conservationists like Bosco and Stewart with the state’s resources and manpower could help transform the efforts of an often-misguided forest department into a vast and purposeful machine.

Given the immense terrain of the Nilgiris, the only restoration efforts that will prove successful are the ones that take the long view — plotted over decades, capable of surviving different governments, researchers, stakeholder conflicts, and whatever other unforeseen problems make it easy to shelve such projects for a later day. If anything about environmental restoration in the twenty-first century is true, it’s got to be that the only way forward is to try things that have little precedent.

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