nature's secrets

How Indian ecologists are finding unknown treasures hidden in the canopies of trees

In the Western Ghats, a bunch of intrepid researchers are climbing up trees to peek into an unexplored world.

Walking into a forest is probably one of the most immersive ecological experiences. It isn’t like walking into any other landscape like a mountain or a desert, both of which introduce their marvels at a deliberate pace. When you step into a forest, it is almost as if the edge zips shut behind you. The trees sieve the bright sunlight into twinkling stars, the soggy ground softens your step and the foliage pushes against the world outside.

Standing under a lofty Cullenia tree, in an evergreen forest in the southern tip of the Western Ghats, I felt less like an observer and more like the observed. Spiders poked out from under leaf litter, and speedy movements caught the corners of my eyes. There was a vague sense that life was apace elsewhere. Somewhere here, a long time ago, Soubadra Devy had stood staring up into the canopy under a shower of half-eaten flowers that rained down on her. The Cullenia held her in its gaze.

The Western Ghat canopy.

Devy is a fellow at the Bengaluru-based Ashoka Trust for Research in Ecology and the Environment, or Atree, and over the past quarter century, neither the tree nor Devy has broken the stare. Her delight in this landscape is unmistakable. She tells stories at every bend of the road up to the forest that is as familiar to her as a well-worn neighbourhood path.

The Cullenia is one of the dominant species in the Kakachi-Kodayar forests in the Kalakad-Mundanthurai Tiger Reserve in Tamil Nadu. Devy specialises in canopy science, an understudied field that investigates what goes in the canopy, the topmost layers of trees: what this mystical space is like, who uses it, how its resources are divided, and how it is changing.

The canopy is a continent unto itself, and the way in which a few Indian scientists have been intrepidly exploring it mimics the manner in which the first visitors might have inspected life on a new land.

First come the surprise encounters and novel experiences; then a survey of the land; thereafter, the discovery of complexities within the new landscape.

Devy, her Atree colleagues T Ganesh and R Ganesan, and their students have been the pioneering scientists from India who have mastered the skills to climb into and explore this last biotic frontier. Thanks to new techniques to access the canopy and the enthusiasm of a few individuals, Indian science is finally able to part the leaves to peek into the curious world up there.

The roof of the forest harbours a major portion of its biodiversity. It is the epicentre of several ecological chains and a critical interface of biomass and gas exchange processes between our planet and the atmosphere: photosynthesis, carbon storage, climate regulation. The canopy is a teeming reservoir of life. The canopy research of Terry Erwin, an entomologist at the Smithsonian Institute who worked in the 1970s, helped revise the global estimate of arthropod species from 1.5 million to 30 million.

Despite its obvious relevance to Earth’s wellbeing, canopies have long gone unseen by scientists. We sent probes to outer space and the deep sea long before we realised that the forest cannot be deciphered from the ground. “It was simply overlooked,” Margaret Lowman, an American pioneer of canopy ecology, said. “People were challenged to dive or travel to outer space but they never quite realised that looking at the base of a tree was extremely different from getting into the canopy. It was only after a few of us did it for the first time, that we were able to exclaim, ‘Wow, this is almost like another planet up here!’”

Tree climbing 

Space explorers

The desire to get on top of things seems fundamental. Citadels, mountaintops, forts, watchtowers: a view from the top is the ultimate domination. It explains scale. To be able to see a whole mountain range, or miles and miles of a jungle, or giant mining pits places our race in context and weighs our impact on this planet. For some, it conveys the fragile nature of our landscape and its sublime beauty. A photo of Earth taken by the crew of Apollo 17, nicknamed the Blue Marble, evoked this sentiment from American scientist James Lovelock: “Suddenly, as a revelation, I saw the Earth as a living planet. The quest to know and understand our planet as one that behaves like something alive, and which has kept a home for us, has been the Grail that beckoned me ever since.”

A similar quest encouraged Seshadri KS, a National University of Singapore researcher who worked with Devy, to get to the canopy starting in 2008. “When you are there, you start seeing things a little differently. You know how little you are. It is a 100-foot tree that has been there for 300-400 years. To me it felt like, I am a human creature who has been around for very little time in the evolutionary timescale.”

Canopy science began with observation, through binoculars and telescopes trained upwards, or by studying scraps of evidence that floated down. It soon led to a few eccentric or risky methods: by training monkeys to collect samples, cutting down trees, some untrained climbing. Such extrapolations were not exactly precise science. Our ancestors might have frolicked in the trees, but it took our species a surprisingly long time to figure out how to get back there.

In the 1970s, the first safe, inexpensive and stable system to access the canopy was devised: the Single Rope technique. A catapult slings a rope across a high branch, which is then used to ascend with the help of carabiners. SRT, however, didn’t make it to India till early this century. It was Lowman who first imparted the skill of climbing to Devy and others. Before that, Devy had employed local tribals, used to climbing tall trees to harvest honey and lichens, to hitch ladders on trees and build platforms up top. In Kalakad-Mundanthurai Tiger Reserve, I saw one tree that still had the remains of an ancient ladder nailed to its trunk.

Rope climbing technique 

Surprise ahoy!

Landings on the continent of the canopy are so novel that the animals don’t scurry away. Devy remembers the first time her head of curls poked through the foliage. “Because the animals don’t expect human beings up there, they are not alarmed. Animals we rarely spotted from the ground were all around.” The encounter rates for every species are significantly higher in the canopy: insects, millipedes, beetles, frogs, squirrels, and birds.

A frog in the canopy

So rich in life is the canopy that a new species can sometimes be discovered without conscious effort. Seshadri found a new frog species, Raorchestes kakachi, when he wasn’t even looking for it. His frog work started while he was looking for epiphytes: plants that grow on trees. Like several ecological discoveries, this happened serendipitously. It was a rainy month, when frogs are most active. “One day, it started raining, and as we were rushing down, I stepped on a branch and I saw something grey jump out of the tree. It was a frog,” he said. “The first time I saw one in the canopy. It occurred to me that all the calls that I was hearing around were probably frogs as well.”

That was the beginning of Seshadri’s frog research – a monitoring programme to document amphibians in the Kakachi-Kodayar forests, paying special attention to canopy frogs. His work went on to expand the list of frog species in Kalakad-Mundanthurai Tiger Reserve from 9 to 25. This was one of the first efforts to monitor amphibians for long-term population dynamics based on their calls. Frogs and toads respond to changes in atmospheric moisture and temperature, so the team wanted to analyse sound recordings, combined with readings from climate data loggers, to understand the effect of climate change on amphibian populations.

Such research is painfully nascent in India. “We are still in the stamp collecting stage, cataloguing stuff,” Seshadri said. “We have no idea how frogs interact. There are definitely three or four species more to be discovered. Someone has to go look for them.” He was demonstrating a canopy ascent as he spoke. I looked up into the canopy as he said this. We were in the quieter hours of the afternoon, and all this talk about the abundant life in the canopy left me with an intense itch to climb.

Frogs form but a small part of the canopy’s diversity. YB Srinivasa, of the Bengaluru-based Institute of Wood Science and Technology, found a new species of scorpion in south Coorg. He also found the canopy to be extremely species-rich for spiders. R Vivek, a postdoc at the National Centre for Biological Sciences, worked with Ganesh to show that the Malabar spiny dormouse, once dubbed an “elusive species”, was found most easily in the canopy. The dormouse is a small mouse-like animal with a bushy tail that is endemic to the Western Ghats. “We learnt that standalone ground-based sampling led to inaccurate generalisations and bias in estimates of richness and abundance for birds and small mammals,” said Vivek.

Other surprises have included finding a new species of arboreal ant and learning of how dependent King Cobras are upon the canopy for their food. “We’re just beginning to find out what a forest is,” Vivek said. “We’re still having ‘aha’ moments in the canopy.”

Canopy geography

How does one describe a new continent? For starters, a physical survey is necessary. What is the topography like? Where does one find shelter and food? Manjari Jain, an assistant professor at the Indian Institute of Science Education and Research in Mohali, puts the geography of the canopy in human terms. “It’s is like a multi-storey building. Each resident has a different apartment at separate levels. In some cases, these residents can move apartments up and down, and some can’t,” said Jain, who has worked in the canopy of the last remaining virgin forests in Kudremukh.

Jain set out to study canopy foliage, a landscape of leaves and branches that had received little attention in science. “We don’t know how much space for food, shelter and mating is available in each layer,” she said. “How much do the bottom and top contribute to photosynthesis? It’s hard work.” Such studies can also quantify how much foliage we have lost, especially in an area such as Kudremukh that has lost massive chunks of forest to mines.

Medinilla Bed

In the forests of Kudremukh, nearly 45% of the total foliage is held in the canopy. Jain was examining the layers of the forest – the floor, the understory and the canopy – because she was studying crickets and their calls. Crickets care a lot about forest architecture. Nearly 70% of the “sitting space” for crickets is provided by specific niches in the understory and the canopy. Some don’t even move during night time, when they are most active.

Jain collaborated with professional climbers to set up recorders in the canopy, so that she could study the “vertical stratification” of crickets –which “floors” they occupied and why. For weeks, she and her assistants hung from trees with speakers, laptops and recorders. She had thought initially that male crickets called out from particular “floors” so that no foliage obstructed their sound, but experiments proved this hypothesis wrong. Jain now thinks that the reason may have to do with food or shelter. “You ask one question and the answer will lead you to three more questions,” she said. “But that’s science.”

The canopy’s unique topography supports a unique resident – epiphytes, plants that grow on trees. It is like suspended landmass – thick mat of branches and roots of creepers trap leaf litter, dried flowers and form a kind of soil. This soil supports unique fauna distinct from that on the forest floor. “Ours was the first study in India – to look at the distribution of epiphytes in a 3D space, which cannot be done from the ground,” said Seshadri. When you look at epiphytes from the ground, you only see them in two dimensions. The canopy gives a nuanced, detailed insight into how these mini ecosystems work.

Epiphyte canopy soil

Joining the dots

Once you acquaint yourself with the landscape and inhabitants of a new continent, what remains to be studied are the complexities of their interactions. Devy’s expeditions have helped decipher the mystery of pollination of 86 tree species. For long periods of time, Devy had to laboriously hand-pollinate several trees because ham-handed assistants turned out to be imprecise. “All flowers open between 4 am and 7 am, and I had to be up there at that time. Sadly, sometimes the bees beat me to it, but it was always fun.”

From the beginning, Devy wanted to get to the top. In spite of peers discouraging her because it is risky and asking her “to work in the shrubs”, she persisted. Devy’s pioneering study unpacked the social bee pollination of canopy trees in Kalakad-Mundanthurai Tiger Reserve. It showed how one tree species, Palaquium ellipticum, was critical for rock bee populations. The flowering of the tree meant a burst of arrival of the rock bees. Most tree species in the tiger reserve are pollinated by two species of bees – the rock bee and the Indian honeybee.

Ecological networks illustrate what the life of a forest is really like. Ganesh and Devy spent years studying the Cullenia exarillata. This gigantic canopy tree flowers from January to April – a resource-scarce time in the forest. “Also the best time for canopy tourism, since you can see several species on one tree,” said Ganesh. The tree’s long, tubular flowers make the branches look like they are wearing furry sweaters; its fruits resemble mini durians.

The study examined the various plant-animal interactions between the Cullenia’s flowers and the animals attracted to them. Ganesh found that this tree is a keystone species, holding up the whole ecosystem. Imagine a delicately balanced Jenga game; this tree would be the piece that holds the mad jumble together.

Since it flowers when most other trees don’t, the Cullenia is a key resource for monkeys, bats, dormice and squirrels, which love its fleshy flowers and nectar. It enables several other species to survive; in exchange, the tree is pollinated at the end of this grand feast.

Fulvous fruit bat 

Research like this, shining a light on the mysteries of deep forest, is essential for forest management, or we risk stumbling through the dark, cluelessly transforming large landscapes forever, not even aware of the damage we wreak. The Indian government is hurtling towards a massive, but poorly planned, afforestation programme. The history of administrative error in such moves is telling. Uttarakhand, for instance, now wants to cut down lakhs of its pine trees because their thoughtless planting has led to a serious forest fire problem. How do you plant a tree when you don’t know what role it plays in the forest? Restoring green cover doesn’t always restore an ecosystem. “When you log a forest, what do you cut?” Devy said. “People don’t see these linkages. A forest, for people, is its animals, not its trees.”

Devy and Ganesh continue their long-term monitoring in Kalakad-Mundanthurai Tiger Reserve, but now they use cameras, recorders and other technology. Their climate change studies can reveal how fluctuating temperatures, rainfall and moisture can affect animal and plant species. Much of the canopy and its inhabitants are extremely vulnerable to changes in climate.

Like most research in India, the field is besieged with problems in receiving forest department permits and funding for long-term studies. Jain admits that she is intimidated at the prospect of applying for new permits. For the past seven years, Devy has been trying to get a permit for a crane in the forest, taking up just four square metres on the forest floor but exponentially increasing the ease of climbing. “I just hope we can get one before I die,” she said, at once enthused by the idea of a crane and disheartened by the process. She is, at present, temporarily grounded by an arm injury, but she wishes she could drop everything to ascend to the canopy and dangle her legs from a moss-ridden branch.

Vivek shares a similar love for these glorious heights. He even has his own rope set. “There is always the allure of climbing,” he said. “Sometimes I go to the outskirts of Bangalore and climb a tree. Lizards, insects... maybe an ant never seen before. As an ecologist, you are trained to observe patterns, processes and fauna and birds – all are agents and actors. It’s the drama of life in front of your eyes.”

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