Bamboo bonfires and biodiversity

Can wildlife and slash-and-burn shifting agriculture coexist? This question led me into remote rainforests of northeast India in 1994 for a field research study in Dampa Tiger Reserve, Mizoram. In December 2013, nearly two decades later, I went there again. From the Anamalai hills in south India, I travelled across the country to initiate a comprehensive bird survey in Dampa, including a resurvey of my old field sites. As a prelude to other writings I will post here in the days ahead, I post below an edited version of an article about my work in Dampa in the mid 1990s. This article first appeared in the May/June 2007 issue of Wildlife Conservation magazine (a remarkable periodical published by the Wildlife Conservation Society, which after a print run of over 112 years, perished with the recession in 2009). Original PDF here.


A jhum fire speeds upslope in a field at the edge of Dampa Tiger Reserve (photo from 1995).

The heat from the fire is intense, even from a hundred metres away. The entire slope is ablaze. Piles of slashed vegetation and tens of thousands of bamboo culms that had sun-dried for three months burn ferociously. The bamboo hisses, crackles, and explodes, audible a mile away. Hot gusts of wind scud the fire upslope, throwing branches and small trees ten metres into the air. High above, unmindful of the billowing fumes, swallows and drongos, in a frenzy of activity, hawk insects. Ash and smoke darken the sky, reducing the sun to a dull orange ball. In twenty minutes, almost as rapidly as it started, the fiery spectacle ends. On the soil, only a blanket of smoldering ash and tree trunks remain.

The fire was kindled by tribal farmers of Teirei, a remote village adjoining tropical rain forest in the Lushai hills of Mizoram State in northeastern India. The farmers practice traditional slash-and-burn shifting agriculture locally known as jhum or law (pronounced lo). Ash is an effective way to enrich the poor soils with nutrients prior to cultivation. The burned patch, significantly, was just within the border of the five hundred square kilometre Dampa Tiger Reserve. This reserve was established in 1989 to protect tigers and other wildlife species such as the hoolock gibbon, capped langur, clouded leopard, hornbills, great slaty woodpeckers, wren-babblers, and other endangered species, many of which are found only in the tropical rainforests of northeast India within the country.


Found only in northeast India within the country, the capped langur is a leaf-eating primate that prefers mature rainforest habitat. (Photo courtesy: Ramki Sreenivasan)

Jhum is a serious conservation issue in northeast India. Between 1989 and 1995, remote-sensing analyses estimated that more than a thousand square kilometres of forests were lost due to jhum in the seven northeastern states. The effects on wildlife are largely unknown because few studies have been done in these often remote, insurgency-ridden parts of India. On the other hand, more than a hundred ethnic communities and well over a quarter of a million families depend upon jhum for their livelihood and economy, frequently cultivating in or at the edge of protected areas, as in Dampa.

A farmer in Teirei village clears his jhum field (photo from 1995), cutting bamboo and pioneer trees in a secondary forest that has regenerated on land that was cultivated and then abandoned ten years earlier.

A farmer in Teirei village clears his jhum field (photo from 1995), cutting bamboo and pioneer trees in a secondary forest that has regenerated on land that was cultivated and then abandoned ten years earlier.

The conservation issues raised by jhum are many and controversial. Many conservationists claim that, by destroying forest cover, jhum causes wildlife declines and extinctions, soil erosion, and drastic environmental changes—most evident when tall, primary rain forest is replaced by crop fields. Others have argued that the effects of jhum may be relatively benign compared to those of terrace cultivation, tea plantations, and monoculture forestry. By maintaining a mosaic of fallows and regenerating forest, jhum may help increase biological diversity at the landscape level. Yet, the critical question is: do species of high conservation value—those that are rare or specialized or have small geographical ranges—benefit or suffer from slash-and-burn cultivation? To unravel the answer, one needs to first understand the cropping patterns and changes that occur in the forest vegetation as a result of jhum.

Although timing of cultivation, types of crops, and agricultural practices of jhum vary in Indian communities, the broad pattern is remarkably similar to slash-and-burn cultivation in southeast Asia and other tropical regions. Until recent times, the enterprise in northeast India has been driven and regulated by the community that controls the land. Each household is allotted a parcel of land between one and four hectares in size. Normally, this would be part of a slope of secondary forest that has been regenerating for five to ten years since the previous cultivation. Tall, mature rainforest is also cleared, but rarely, owing to the scarcity of such forest and the difficulties of clearing.

When mature rainforest is cleared, as occasionally happens, all vegetation including tall, mature trees are cut, to the detriment of species dependent on undisturbed habitat. (Photo courtesy: S. U. Saravanakumar)

After the cut, in January or February, the slash dries on the hills until April, when it is burned just before the onset of pre-monsoon rains. Farmers then sow several varieties of rice, their mainstay, along with more than a dozen other crops, including eggplants, beans, and tubers, as well as some cash crops such as tobacco and chilli peppers. A busy season of weeding and multiple harvests follows until October, when the spent field is abandoned. Fields are rarely cultivated for more than a year, because one round of cultivation severely depletes the soil. The next year and in successive years, new areas are cleared, until the vegetation in the first site regenerates sufficiently to permit cultivation again—usually within ten years. But is this a sufficient amount of time for native rainforest plants and wildlife to recover?

To observe a regenerating forest from the time it is cleared to when the vegetation or a semblance of it recovers is practically impossible within the lifetime of a rainforest biologist. Field biologists therefore sometimes use a short-cut solution: they study various sites cleared and abandoned at different times in the past, which currently represent different ages and stages of forest regeneration, a method called ‘space-for-time substitution’. Such an opportunity existed in Dampa. So, to study changes in vegetation and wildlife here, I surveyed sites that had regenerated for between one and 100 years and compared them to rainforest that had never been cleared. It was a special and awe-inspiring experience, like a virtual voyage through time, visualizing the birth, growth, death, and vicissitudes of a rainforest and the plants and animals in it—a fascinating subject for any rainforest biologist. After months of fieldwork, with the data from transects and plots in the hand, the trajectory of changes could be pieced together.

Soon after a field is abandoned, weeds, grasses, surviving crop plants, and bamboos sprouting from underground rhizomes run amok, creating a dense and vigorous tangle that at first threatens to smother forest regeneration.

Open fallow: a jhum field in its first year of abandonment after cultivation.

Open fallow: a jhum field in its first year of abandonment after cultivation.

The grey bush chat is a bird of the open fallows.

The grey bush chat is a bird of the open fallows.

In these open fields with hardly any canopy, common and widespread wildlife proliferates. The ubiquitous red-vented bulbul, common tailorbird, white-rumped munia, and grey bush chat thrive in the open land that has lain fallow for one year. Most rainforest species avoid these areas, although the occasional pigeon or woodpecker may briefly visit an isolated tree standing dry and forlorn in the field. The common hoary-bellied squirrel scurries on the ground, picking at choice bits of food. The grass looks good for ungulates, but the shy barking deer and sambar seldom venture here, for they may be snared or shot.

Fortunately, this situation does not last long. The vegetation recovers with astonishing rapidity. The open, weedy fallows rapidly give way to bamboo forests. In five years, the bamboo, along with pioneer trees such as Macaranga and Trema, form dense stands that reach ten feet and higher. Wildlife from the surrounding landscape begins to colonize. Understorey birds are among the first to appear in sizable numbers: rainforest babblers, warblers, flycatchers, and bulbuls. If lucky, one might also see the bamboo-loving woodpeckers: the pale-headed woodpecker and the white-browed piculet, clinging to the smooth culms, searching for insects.


In the early years of forest succession, bamboos establish rapidly and dominate the vegetation, along with some pioneer trees.

Bamboos reign supreme for many years. In Mizoram, the bamboo Melocanna bambusoides dominates regenerating fallows for at least the first thirty years. As time passes, more bird species appear, and the air is alive with their calls. Some arboreal mammals, too, venture into tall bamboo and secondary forests that have been allowed to regenerate for ten years or more, particularly if they are near mature rain forests. Phayre’s leaf monkeys—carrying a permanent expression of amazement due to the white circles around their eyes—forage in troops of a dozen or so individuals in the canopy. They feed on leaves of trees and climbers, often nibbling only at the leaf petiole and discarding the rest. The sprightly, dark-furred and red-bellied Pallas’s squirrel, and even a few of the cautious black-and-white Malayan giant squirrel scamper through the canopy or pause to gaze suspiciously at observers. As bamboos and pioneer trees grow taller and larger, rainforest tree seedlings sprout and flourish in their shade.

If left undisturbed, the slow-growing saplings eventually take over after the bamboos flower en masse and die. One site, that had regenerated for a hundred years, contained mostly tall rainforest trees and lianas with little trace of bamboo. Here, and even more so in primary rainforest that has never been cleared, plants and animals achieve their highest diversity.

Mature rainforest in Dampa Tiger Reserve

Mature rainforest in Dampa Tiger Reserve

Camping in a cave by the Tuichar River, deep in primary rainforest, I could experience this first hand every day. Here were lofty rainforests with their profusion of life. In a single day’s observation at a wild fig tree fruiting just above my camp, I saw four species of primates including a family of hoolock gibbons, five species of squirrels, three species of green pigeons in large flocks, great, oriental pied, and wreathed hornbills, imperial pigeons, Asian fairy bluebirds, and, surprisingly, even a flock of laughingthrushes that had ascended into the canopy. In stark contrast, fig trees that were left standing alone and tall above a jhum fallow or a bamboo forest held only a vestige of these spectacular gatherings, fewer species, and mostly common ones.

When regenerating bamboo forests are cleared for cultivation within ten years, as usually happens in northeast India, rainforest recovery is interrupted and the land undergoes another of the endless cycles of bamboo. Due to the spread of shifting cultivation in the region, which means short fallow cycles of fewer than ten years, huge areas are under this “arrested succession” of dense, almost monotypic bamboo forests. Besides having fewer species, these bamboo forests are also prone to destructive fires after bamboos flower en masse and dry up. Nearly forty years after the last bamboo flowering during the late 1960s, vast areas of Mizoram underwent a spectacular bout of flowering during 2006 – 2007.

Short-cycle jhum may result in large areas of arrested successional bamboo forests

Short-cycle jhum may result in large areas of arrested successional bamboo forests.

The wildlife species that suffer most due to jhum are often those most critical from a conservation point of view―those that are rare, specialised, or restricted to the northeast Indian rainforests. India’s only ape, the hoolock gibbon, and other arboreal mammals such as the capped langur and the Malayan giant squirrel, occur only in mature rainforest and are locally extinct or very rare in jhum-altered landscape. This patterns of change was also evident among the bird species. The number of bird species increases with forest regeneration, rapidly at first, then slowly to reach maximum diversity and abundance in the 100-year-old mature forest and undisturbed tropical rainforest. Moreover, the mix of bird species or bird community composition also changed with time, achieving by a hundred years a high similarity with primary forest.

Where does this leave the claim that jhum increases biological diversity in the landscape? Obviously, more species can be accommodated in a tropical rainforest landscape when new habitats such as open fallows and dense bamboo forests are created by jhum. The additional species appearing in the landscape are, however, mostly common and widespread species, of open scrub or dry deciduous forest habitats. Many species considered more important for conservation—rare, endangered, restricted-range, and habitat-specialist species—decline or suffer from habitat alteration due to jhum. The increase in biological diversity in the landscape may this come at the cost of such rainforest species.

Still, any assessment of the effects of jhum needs to consider livelihood needs and traditional rights of the people who practice jhum cultivation. Social scientists and activists have justifiably championed the cause of indigenous peoples. Yet, defining what is traditional and who is indigenous in communities undergoing rapid socioeconomic changes, market integration, and migration is difficult. In and around Dampa Tiger Reserve, as in other parts of northeast India, the human population has soared in recent years and includes many settlers from other parts of Mizoram, Tripura, Nepal, and Bangladesh, all with their own customs and traditions, and far removed from places where their traditions initially evolved. Over the last century, a large proportion of the people in Mizoram have converted from animism to Christianity. With road- and market-penetration, human societies are not static, but change dynamically.

Village of Damparengpui (December 2013)

Village of Damparengpui (December 2013)

Jhum is not the only problem for wildlife conservation in northeast India. Large-scale logging by the government, illegal timber poaching, and conversion of rainforests to monoculture plantations of tea and teak—widespread ecological ills caused by state and private, mostly non-tribal, interests—consume precious land and forest. As a consequence, the burgeoning tribal populations, growing at among the fastest rates within India, are forced to clear remnant forest tracts and to cultivate at shorter fallow periods. And so, the vicious cycle of arrested bamboo succession continues. If wildlife conservation in India’s northeast is to be effective, all the forces of landscape change must be addressed, squarely and urgently.

A teak monoculture established in the buffer zone of Dampa by the Mizoram Forest Department in erstwhile community jhum lands.

A teak monoculture established in the buffer zone of Dampa by the Mizoram Forest Department in erstwhile community jhum lands.

Although it is easy to say that from a biological perspective one needs undisturbed, preferably large tropical rain forests, it is not an easy conservation objective to achieve. Such areas are scarce, and one is often left with only various-sized, disturbed fragments of rainforest in a jhum-dominated landscape. There are alternatives. In Meghalaya, tribal communities protect small, sacred groves. In Mizoram, thanks to state laws passed in the 1960s, villagers use a network of “supply” forests under regulated use for biomass harvests. More infrequently, a few “safety” forests exist, fringes around villages created to protect them from jhum fires. These areas are rapidly diminishing or vanishing as villages grow and lifestyles change. It is important to include these areas, along with agriculture and plantations, within the ambit of conservation planning for it to be effective at the landscape scale.

Conservation efforts in northeast India cannot proceed without due consideration of the legitimate needs of the millions of poor farmers, such as the people of Teirei, who depend on jhum for their livelihoods. Shifting cultivation is an organic system of multiple cropping well adapted to areas of high rainfall. Alteration of jhum to mechanized or terraced agriculture or monoculture plantations, even if possible, may be even worse for biological diversity and food security.

Forest cleared for establishment of monoculture rubber plantation: worse than jhum?

Forest cleared for establishment of monoculture rubber plantation: worse than jhum?

In the final reckoning, many forms of land use and forest types will be a part of the landscapes of the future in this region. It is also evident that in parts of northeast India, intense, short-cycle jhum and wildlife conservation are largely incompatible. For wildlife conservation to be a reality, there is one type of land-use and forest that is essential in this mix: protected sites with primary rainforest.

In Dampa Tiger Reserve, conservation efforts have been promising. After initial difficulties, eleven villages with nearly five hundred families located inside the sanctuary were resettled on the periphery in 1989. Today, jhum is mainly restricted to the buffer zone and areas outside sanctuary boundaries. A large project implemented through the local government and village councils has been underway in Mizoram to develop and sustain alternate livelihoods for the villagers, with the goal of finding alternatives to jhum, and ostensibly to minimize pressures on forests.

Meanwhile, scientific surveys continue to reveal the extraordinary diversity in these rainforests. Using camera-traps, forest staff have obtained photographs of the rare and elusive marbled cat and the clouded leopard. A survey to catalogue resident reptiles and amphibians has revealed the presence of several rare and endemic species, including some that could be new to science. In many ways, Dampa represents a tantalizing pocket of hope for what is possible in these remarkable rain forests.

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