BY ANURA GUNASEKERA
Monoculture diminishes biodiversity whilst a multi-dimensional culture permits a wider variety of species, both fauna and flora. A distinctive feature of all monoculture, is the regular application of chemical fertiliser – both soil and foliar – as well as fungicides, pesticides, weedicides and other inorganic substances, which invigorate the main crop whilst suppressing competing fauna and flora. In a scenario of increasing food production to feed the planet, regular applications of chemical fertiliser, essential for improved crop productivity and soil fertility, is an unavoidable evil. However, its long-term use is adverse to soil structure and the microorganisms which enrich overall soil biohealth and biodiversity. Moisture retention is also inhibited, encouraging quicker run-off and erosion during heavy rain.
Similarly, chemical preparations employed to control targeted diseases, pests and competing fauna, being generally non-discriminatory in impact, destroy other species as well. Monoculture permits only designated crops and any other flora or fauna sheltering within, becomes an enemy.
In Sri Lanka prime examples of large-scale monoculture are rice, tea, rubber and coconut. Bear in mind that the land now occupied by tea, rubber and coconut, was largely species – rich, virgin forest – in the not too distant past. Of the four, coconut is relatively more environmentally friendly than the others. Rice cultivation, which requires intermittent flooding of large areas of land, apparently results in major climate change outcomes due to methane and nitrous oxide emissions, factors not normally featured in the discussion around the crop. Rubber plantations are technically considered to be “renewable forests” but its thick canopy prevents any other cultivation, or an understory, completely ruling out biodiversity.
In the last decade, oil palm cultivation has also entered the equation but in any discussion on that contentious crop, one must bear in mind that in Sri Lanka, oil palm is simply a replacement for rubber. However, oil palm, by nature of its tree configuration and the related field agricultural practices, permits less biodiversity than any of the other plantation monocrops.
All of the above comprises a massive field for touchy debate, compressed into a few paragraphs. In this writing, delivered with a clear understanding and an appreciation of the importance of tea production to the national economy, it is a preamble to some observations on biodiversity in tea plantations.
When I joined the plantation industry in the 1960s, a distinctive feature of most well-managed tea plantations was the presence of both high and low shade, the former generally of Grevillea Robusta or Albizia Chinensis and the latter species of Acacia, Dadap, depending on the elevation. These trees provided perching and nesting locations for a very wide range of bird species. At higher elevations, in fields exposed to strong winds, there would be thick rows of Acacia wind belts. Those apart, within the plantations were forested ravines with streams running through them, constituting separate microsystems. Whilst the British entrepreneurs decimated hundreds of thousands of acres of virgin forest in the opening of plantations, paradoxically, they were fiercely protective of the natural forest features within the plantations, and scrupulous about the maintenance of all types of shade trees.
Thus, the denudation of the virgin forest for the planting of tea birthed a different biodiversity, specially adapted to the monoculture scenario. The larger animals retreated to what was left of the forest cover, generally at the higher elevations and on the periphery of the tea cultivation, whilst the smaller animals, especially rodents, found shelter in the forested ravines and the dense tea. Bird life, because of unrestricted mobility, had a free run between ecosystems. Hence, over time, a degree of plantation ecosystem stability, or a different normal, was created; that is, till its disruption by the regular use of synthetic fertiliser, fungicides, weedicides, pesticides and felling of trees within the plantation.
In my era, field rounds were mostly on foot and that facilitated observation. The commonest were large flocks of the Hill White Eye feeding off insects within the tea. The Scimitar Babbler was abundant, as were the Pied Shrike, Great Tit, the Tailor bird, Flowerpeckers, Sunbirds, and a variety of Prinias and Flycatchers. The Spot Winged Thrush and the Button Quail were frequent sightings despite stealthy habits, whilst the Pied Thrush, the Indian Pitta, the Kashmiri Flycatcher and Wagtails were regular winter visitors. The Hoopoe was common in the early part of the year.
Tea pluckers would frequently disturb large flocks of Rufous Babblers, often numbering 30-40, feeding in the tea which, in my time, was mostly of dense, heterogeneous Seedling Tea (ST). Its compact branching and wide bush-base provided a multi-layered habitat for multiple species of grubs, caterpillars, insects and the like, and secure nesting points for Tailor Birds, Prinias, and Babblers. The small fauna was food for bird life, a sustainable method of biological pest control.
The low shade was home to a wide range of Bulbuls and Minivets, whilst the canopied high shade sustained Leaf Birds, Ioras, Barbets and Woodpeckers. The wooded ravines provided hunting for Black Eagles and homes for Hornbills, Jungle Fowl, elusive Spur Fowl, and a range of rodents and jackals. On a sunny day, apart from the many soaring raptors, I have recorded over 40 species before lunch, by casual observation, without the use of field glasses.
In the last few decades, in my travels in the plantations, especially in the high-grown districts, I have noticed a gradual, but alarming diminution of such sightings, both in terms of species and numbers.
In my view it started in the 1950s, with the large-scale replacement of seedling with the homogeneous, vegetatively propagated (VP) clonal tea. The very uniform VP tea, whilst being more productive, does not have either the same branch density or the bush configuration of ST and, thus, offers a more restricted micro habitat for fauna.
The territory for perching birds has been limited by the gradual diminution of both low and high shade, resulting from a combination of non-replacement of tree casualties and designed harvesting. In many tea plantation areas, the commercial felling of Grevillea (in the high and medium grown sectors) and Albizzia (low country), appears to be a widely-practised revenue generation strategy by both cash-strapped companies and individual owners. Regrettably, replacement seems to be an exception.
The regular application of fungicides and pesticides has diminished insects and related small species, disrupting the food chain which sustained many of the species described above. It has also contributed to environmental toxicity, unsettling what was a highly ramified, symbiotic, relationship equilibrium within a narrow ecosystem. As for weedicides, decades ago, weed control in tea was achieved with a judicious combination of manual and chemical weeding. However, today, on account of worker scarcity, that strategy has been replaced by drench spraying of potent chemicals which kill indiscriminately. The consequences are too wide-ranging to be addressed in this writing.
Till about the late 1970s, plantation companies were permitted to fell virgin jungle on the periphery of the plantations, even at high elevations, to feed internal fuel needs. The denuded areas were reforested with eucalyptus and pinus species. Both, due to growth configuration and toxic resin content, constitute highly restrictive micro ecosystems with very limited opportunities for species diversity. Pinus in particular, because of its decay-resistant needle fall which thickly carpets the forest floor, prevents the growth of any type of understory whilst accelerating rainwater runoff.
As for the many wooded ravines and swampy areas within plantations, they have been steadily encroached upon and in many regions replaced by vegetable cultivation. The waterways within have been polluted by leached chemical fertiliser and the drip-down of foliar applications of trace elements, fungicides, weedicides and pesticides.
Ceylon tea is justifiably considered the cleanest in the world, with its Minimum Residue Levels (MRL’s) of specified toxins conforming to the most stringent international market requirements. Yet, in retrospect, a crop which identifies Sri Lanka globally, has had its long-term impact on the environment. Strategies for mitigation, rehabilitation, restoration and protection are many but need to be discussed separately. Ideally, they should comprise a state-mandated national policy for compulsory implementation in all plantation areas.
(The writer is a retired plantation industry specialist, an amateur herpetologist, a keen bird-watcher and a passionate conservationist)
The history of wildlife protection in Sri Lanka is almost synonymous with that of the Wildlife and Nature Protection Society of Sri Lanka. At 128 years old, the WNPS is the third oldest non-governmental organisation of its kind in the world and was responsible for the setting up of the Wilpattu and Yala National Parks in Sri Lanka, and of the formation of the Department of Wildlife Conservation.