Shola landscape - Bob & Tanya

Not all aliens are villains: Shola Grasslands, Bob, & Tanya

If you grew up in the 80s or 90s in southern India, or watched movies from there (or even Bollywood), chances are you've seen a romantic song picturised on rolling grassy hills. Very likely, this is the Shola forest-grassland habitat. The landscape is spectacular — rolling grasslands with forests scattered through them — and this is probably what drew the film industry here in the first place. Tamil director Mani Ratnam set several classics, including Thiruda Thiruda, Dil Se, and Kannathil Muthamittal, in this landscape. Most people encountered the Shola through movies, watching protagonists run through grassy hills and between pine trees. This story is about some of my own observations on the intricacies of this landscape.


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'Shola' describes wet evergreen forests, and more specifically the high-elevation, mountain-top cloud forests of the Western Ghats. These cloud forests draw most of their moisture directly from clouds through orographic effects, skipping the intermediate step of rainfall. It's common to go days without rain here and still see streams gushing from the highest mountains — water moving straight from cloud to mountain. Over time, this cool, wet climate has produced a fascinating habitat matrix: forest patches in the valleys, grasslands spread across the landscape. Together, they're known as Shola.
Both features — forest and grassland — are natural and have existed for thousands of years, and recent research shows that the specific contours of the mountains shape how much of an area becomes forest versus grassland. The habitat's ecological value lies not only in the unique biodiversity it holds but in the fact that it is the source of several south Indian rivers.
Today, people strongly associate the Western Ghats with pine and eucalyptus. Some even assume the name Nilgiris comes from eucalyptus, since eucalyptus oil is popularly sold as 'Nilgiri oil'. In fact, neither pine nor eucalyptus is native to southern India — both were planted here alongside several species of Acacia, first by colonial forest managers and later by us, to feed various timber industries. It was done with the best intentions of the time, but unfortunately, without accounting for the fact that we were planting some of the world's most aggressive invasive species (by IUCN's current classification). Before long, large parts of the landscape — originally grassland — had been taken over by these timber trees.
People like Rom Whitaker and Ian Lockwood, who trekked these hills in the 70s and 80s, walked through rolling grasslands that have since become dense woodland. The change wasn't sudden — it unfolded over decades. It occurred in the Nilgiris and in Munnar too, but nowhere as drastically as in the Palani hills. These are three separate mountain ranges, each anchored by its own hill station: Ooty in the Nilgiris, Munnar in the Anamalais, Kodaikanal in the Palanis. In the Palani hills, over 60% of the landscape shifted from grassland to timber stand.
Conservation through the 80s and 90s was largely focused on protecting forests — rainforest conservation, in particular, was considered paramount. Two travellers from the UK, Robert Stewart and Tanya Balcar, settled in the Palani Hills, inspired by the botanical work of Father K.M. Matthew, and began restoring degraded forest patches. But the longer they spent in the landscape, the more they noticed. The exotic timber trees — Acacia, eucalyptus, pine — weren't staying put; they were spreading across the Palani hills, mostly into the grasslands. Eventually, Bob and Tanya decided the grasslands needed help and began restoring them too — one of the few such efforts at the time, likely inspired in part by parallel work at the Nilgiris' Gurukula Botanical Garden. These observations, in turn, led to sharper ecological insights.
They also noticed something else: native Shola trees had begun growing in the understorey of these exotic stands. Over decades, in some timber plantations, these native seedlings grew tall enough to break through the canopy. These are 'pioneer' species — fast-growing generalists that typically colonise forest edges. In 2012, while I was doing fieldwork in the landscape, Bob and Tanya took me to one such patch, Blackburn Shola. Native and non-native trees stood side by side, sometimes at similar heights and girths — ecological succession happening in fast-forward. This kind of rapid change is rare in Shola habitats, where trees are thought to grow painfully slowly. Walking through the stand, the questions piled up: could we even call this a forest? Some of it had been planted, yet many native trees were thriving in its understorey, in turn supporting other biodiversity. Did the landscape's threatened, endemic species even register the difference between native and non-native?
Bob and Tanya also told me how hard it was to explain ecological succession to forest managers. A few years later, they had me invited to a meeting with several of them. It became clear immediately that the story in most managers' minds was very different from the one Bob and Tanya had pieced together on the ground. The prevailing view was that alien, non-native species were encroaching on and taking over natural forests — not entirely wrong, but missing crucial detail. Many managers believed exotic invasives were invading Shola forest itself. Bob and Tanya, from their own observations, argued this was impossible: what looked like invasion was in fact native, forest-edge species growing rapidly in the shade of the exotics, eventually outgrowing them. To an untrained eye, a mix of native and non-native trees looked like exotics taking over natives. Bob and Tanya believed the opposite was closer to the truth.
I remember them laying all this out at a day-long informal meeting in Bangalore in 2014. Several of us who had spent years working in Shola habitats were there — Milind Bunyan (ATREE), Arundhati Das (now at NCBS), Jayashree Ratnam (NCBS), Nandini Rajamani (IISER Tirupati) — yet none of us had made these detailed natural history observations, or noticed the intricacies Bob and Tanya described. Everything they said made sense, but we were still a little disbelieving. There was no scientific data behind any of it yet. Was this really true? Could it be? And if it was — what did it mean for the habitat and the species living in it? Could we ever set it right? Should we even try?
The questions split along two lines — some purely scientific, others philosophical. What counts as native, non-native, or even 'original' habitat? The Shola's inherently complex nature made this harder still. Research has long shown the habitat is biphasic — both forest and grassland states are natural, and both have existed for millions of years. But the landscape has never been static: forests and grasslands expand and contract over millennia as the climate shifts through ice ages. In drier periods, grass dominates and forest recedes; in wetter ones, the reverse. This has been beautifully demonstrated by researchers who cored into the soil and reconstructed past habitats from the pollen preserved at different depths. So 'original' is relative to whatever point in time you choose. This also undercuts the old idea of a 'climax' community — a term ecologists had largely abandoned, though it lingered in casual use for the Shola. We now know most locations here have been forest at one point and grassland at another.
What was strangely missing, though, was a clear picture of the habitat's current state. How much forest actually remained, and at what sizes? Such data was hard to come by in the late 90s and early 2000s — Google Earth wasn't yet offering high-resolution imagery for this part of the world, and satellite data was expensive. I remember trying, unsuccessfully, to convince several labs with the right expertise to invest in detailed field-survey-based mapping of the landscape.
The spread of woody invasives — Acacia, eucalyptus, pine — added another layer to the puzzle. By 2015, some satellite imagery had become freely available, and Ian Lockwood published a compelling blog post visually interpreting imagery from Kodaikanal to trace timber plantations across the landscape. Inspired by his work, and by Bob and Tanya's descriptions, several of us from the Bangalore meeting teamed up with Ian and two students to run a satellite-based analysis of the region. The questions were simple: what was the current state of the grasslands? Had forests been cleared to make way for timber? After a year and a half of fieldwork and analysis, the answers were striking. From the 1970s to 2017, forest cover had remained essentially stable, and almost every timber plantation had been established on grassland, not forest. But not all of it had been planted by us. A second key finding was that these stands kept expanding even after planting had stopped — clear evidence of ongoing invasion. Tree felling itself had ended in 1996, after the Supreme Court of India's landmark ruling that defined 'forest' broadly enough to halt felling even outside protected areas. Once felling stopped, forest departments stopped planting these trees too, meaning any spread afterward was almost certainly invasion. Fittingly, one of the species most widely planted, Black Wattle (Acacia mearnsii), was declared one of the world's most invasive trees in 2007.
The findings had real management weight. The conservation instinct of the day, one many of us shared, was to restore forest — remove the timber trees, replant native forest species. That work had already begun in several places. But our data pointed the other way: these invaded areas should be restored to grassland, not forest. Historically, grasslands had been dismissed as 'wastelands', unworthy of conservation attention, so this was a genuine paradigm shift — one that state forest departments seemed to be gradually adopting. In Kerala, the devastating floods of 2017 helped push this shift, strengthening the case for landscape-wide removal of exotics and grassland restoration. In Tamil Nadu, a public interest litigation before the Madras High Court sought the removal of exotic species from the hills; the Court, recognising the complexity involved, appointed a scientific committee to advise on invasive species management.
That still left the trickiest category: mixed stands of invasive timber and native Shola trees, complicated both ecologically and in terms of what to do about them. Understanding how they formed might help. Researchers like Arundhati Das (now at NCBS) and Ravi Kiran (now at BSI) had built entire PhDs studying plant communities in Shola forests, and never once found invasive timber species inside intact native forest patches. Their work wasn't designed to test Bob and Tanya's hypothesis directly, but it fit: the structure of the timber stands they studied showed young native Shola trees regenerating within them — not the other way around.
Joachim Schmerbeck, a forest ecologist then at TERI University, and his students surveyed hundreds of vegetation plots and found the same pattern: multiple species regenerating in the understorey of timber stands, effectively using them as nurseries. This isn't a new discovery globally — conservation managers in South Africa noticed it decades ago and turned it into a restoration strategy, deliberately planting fast-growing Acacia to nurse native trees before removing the Acacia and leaving a native stand behind. It's ecological succession, harnessed for restoration — and, notably, invasion is itself a form of succession; here, managers were simply pointing it toward a better outcome.
But Bob and Tanya's model — leaving the old mixed stands alone to support native biodiversity — had an obvious catch: how would the exotics ever be removed, given they could still seed invasion elsewhere? Coincidentally, they'd also noticed that many of the older timber trees were dying, some from a pathogenic fungus, Botryosphaeria, others from natural causes. They recognised that invaded grasslands urgently needed restoring, or the landscape would keep losing ground. But their view of the mixed stands, where natives were regenerating under timber, was more conflicted. On balance, they felt the exotics were doing real damage — mainly to grasslands — while also helping native biodiversity regenerate elsewhere, and that left alone, the exotic timber might eventually die off and benefit the forest anyway. It was a nuanced position, not one everyone accepted easily — perhaps wishful, hoping for some upside from invasives; perhaps just pragmatic, since removing every exotic from the whole landscape was never realistic. Why not, then, leave alone the areas where they were doing some good?
Prasenjeet Yadav, a photographer documenting these debates, and I spent several days talking through it with Bob and Tanya, trying to distill their thinking into something like a restoration policy. What emerged were four landscape-age stages, tracking the successional path of invasion: pristine grassland, young invasion, intermediate-age stands, and mature plantation.
For Bob and Tanya, the core priority was protecting intact grassland from further invasion. Next came young invasion — grassland with newly established saplings — since these would soon mature and choke out the grass beneath them, and since removing small saplings was cheap and easy, restoring large areas for relatively little effort. In some places, old plantings still had grass surviving on the floor; removing the trees here would let the grass recover quickly too. Last on their list, and the most contentious, were the old, mature timber stands with no grass left underneath. Bob and Tanya believed these would largely resolve themselves over time, and worried that large-scale removal here would also destroy native biodiversity that had since taken root. Much of this thinking took shape on paper, in a bar in Munnar, after a long field day with Prasenjeet and Uma Ramakrishnan — still just an idea at that point, with no clear path to the ground. That changed in a meeting with the Dindigul Conservator, who was blunt: without a map clearly showing high- versus low-priority areas, none of this was actionable for a forest manager.
That feedback sent us back to the satellite imagery team, where Milind Bunyan (ATREE) found clever ways to distinguish young from old invasion, aligning the mapping with Bob and Tanya's restoration stages. The numbers were striking: there was twice as much invaded land to restore as there was intact native grassland left. We shared the data with forest departments in Kerala and Tamil Nadu, and I later had the chance to serve on the Madras High Court's invasives committee, through which this data reached the Tamil Nadu government as well. Both states drew significantly on it in shaping restoration policy, and today both run large grassland-restoration sites, testing various methods of removal and replanting. How it all plays out remains to be seen.
Meanwhile, my team at IISER Tirupati began working in the Palani Hills on several fronts. Jobin Varughese has led work on how native birds use invasive timber stands. Ashwin Warudkar is studying how the changed landscape might affect disease spread, and Chiti Arvind is looking at whether bird song itself is shifting with it. Several master's and undergraduate students have chipped in on smaller pieces of the puzzle too. But while all of this progress unfolded by 2022, Bob and Tanya weren't around to see it. Tanya passed away in 2017, Bob two years later, in 2019.
For Bob and Tanya — 'aliens' themselves in this landscape — the demonisation of exotic species and the calls for their wholesale removal must have struck close to home. After three decades spent conserving the Shola, their hardest fight wasn't ecological but bureaucratic: the constant fear of being asked to leave India, and the repeated obstacles they hit trying to gain citizenship despite years of conservation work and several awards. We never spoke about it directly, but I sometimes wonder if they saw something of themselves in the exotics of this landscape — arrivals shaped by circumstance, who nonetheless made it home. They gave so many of us researchers extraordinary clarity through their natural history observations, before quietly making their way out.
Two decades after my PhD fieldwork, walking through the same grasslands where Mani Ratnam's cast once ran, I found myself thinking: they certainly couldn't run here now. Much of the landscape has disappeared into dense stands of invasive trees.