Aug 23, 2022


  • Mitigating the impact of monoculture on biodiversity

By Anura Gunasekera


For this article, I am using my previous article, “Plantation Monoculture and Biodiversity” (published in The Morning Brunch on 4 April) as the launching pad. Whilst in the earlier article, I dealt with the impact of plantation monoculture on biodiversity, in this, I shall address the mitigation of those consequences.

To the farming community, historically, the forest has been a barrier to crop expansion, and also, a potential source of animal incursion into food crops. Hence, the denudation of natural forest cover has marched, hand-in-hand, with the expansion of mono-crops. Deforestation is an unfortunate symbol of human dominance over nature, as is the domestication of wild animals. The former reduced woodland and natural grassland to fields of wheat and barley, whilst the latter transformed the wolf, the aurochs, and the wild boar to the Alsatian, the Jersey milker, and bacon and sausage, respectively. Oversimplifications perhaps, but useful analogies for this writing.

The decline in the closed canopy forest cover in Ceylon from 80% of the land extent in 1830 to around 17% in 2020, coincides with the emergence of capitalist agriculture, when the first coffee plantations were opened up, followed later by tea and rubber. Coconut will not feature in this writing, as that crop has been around as a commercial cultivation for perhaps the last twenty centuries.

More than any other plantation crop, tea, due to its configuration and cultivation practices, would lend itself far more easily to environmentally beneficial management, and reforestation, despite its all-embracing occupation of land. For best results, tea needs the protection of both high and low shade. To mitigate the impact of higher ambient temperatures, and the quicker evaporation of moisture, shade is more important at lower elevations, than at higher elevations. High shade at high elevations is commonly provided by Grevillea Robusta, and low-shade by Acacia (Decurrens or Pruinosa), Dadap (Erythrina) and Calliandra, and at lower elevations by Albizia Chinensis and Gliriicidia respectively.

The very dense low-level canopy of tea, and its thick branching constitute a specially adapted ecosystem for many types of insects, grubs, moths, butterflies, small birds and rodents. The low-shade provides support for perching birds whilst the high-shade harbours the larger predatory species. However, with the gradual reduction in shade, encroachment of ravines, and the intensification of chemical usage, biodiversity in the plantations has declined sharply.


Restoration of high and low shade

The most beneficial method of restoring the balance would be the restoration of both high shade and low shade in all tea plantations. Decades ago, it was a standard practice in all well-run plantations to address this issue, at the time of tea field pruning; every four to five years at the higher elevations, three to four years in the mid-levels, and two to three years in the low country. However, it is evident from the generally sparse shade tree growth across our plantations, that this practice has been relegated in importance, in both the company and smallholder sector. Intensified commercial felling of shade trees in recent times has made the situation worse.

Disturbing aspects of commercial felling of shade trees are the lack of selectivity, and the general absence of a replacement strategy, unlike the practice decades ago. Ideally, shade-tree replacement should be made mandatory by State plantation regulatory bodies, and compliance ensured in both the companies and smallholder sector overall through annual inspections, with penalties imposed for non-conformity.

The annual lopping of low shade (Dadap, Acacia, Gliricidia) generally timed for the approach of the main monsoon provided soil-enriching mulch. The high-shade was also pollarded at intervals, though not annually.

In my earlier article I referred to wind-breaks in tea, especially on exposed mountain slopes. Such wind-breaks, planted either along the contour, or at right angles to the tea rows, apart from wind-damage protection, serve as independent mini-ecosystems. An appropriate parallel would be the “hedgerows”, which are a distinctive feature of farmlands across Britain and other countries in Europe, a system successfully adopted in Californian and Australian vineyards as well.

They provide flowers and pollen for insects, nesting sites for birds, and stimulate predator diversity, whilst offering alternate hosts to pests. They also constitute barriers to the movement of pests. Such hedgerows, in some locations such as Devon, England, which I have inspected during a guided tour, are close to a 1,000 years old, retained in their original form by successive generations of farmers. In many of those countries, strictly implemented statutes ensure their conservation. These hedgerows have been scientifically proven to hold highly beneficial and productive mini-ecosystems within themselves.

Intensified shade in tea may result in a slight diminution in yield, and the enhanced risk of fungal diseases – for instance “Blister Blight” – at higher elevations. However, those are manageable issues, and the positives far outweigh the negatives.


Endless possibilities

An essential aspect of a re-wilding strategy would be the restoration of the vegetation of the ravines within the plantations with a wide range of flora, but not with species specifically used for shade in the tea. Varieties of fast-growing bamboo and grasses, along the central stream edges and flowering trees, such as African Tulip – Spathodea Campanulata, Jacaranda, at all elevations, and species such as Kumbuk and Dipterocarpus – Hora – at lower elevations, would be ideal, bearing in mind that these trees would not be considered for felling at any time.

Most large plantations, especially the company-owned properties, carry aged, low-yielding seedling tea extents – possibly about 30% of the total RPC extent – which are either not regularly harvested due to lack of labour, or abandoned, as steep terrain, and poor soil conditions have rendered replanting with new clones (Vegetatively Propagated or VP) economically unfeasible. Those areas would be ideal for re-forestation with select species, excluding Eucalyptus, Pinus, and coniferous species, which do not lend themselves to biodiversity.

In a flora-rich tropical country such as ours, reliance on imported species with limited utility value and proven barriers to the promotion of biodiversity is decidedly irresponsible. Fast growing flowering-fruiting species would be best, as such flora are able to support a wide range of animal/insect and bird life. Reverting to indigenous forest species that carry the above characteristics, subject to elevational suitability, would be the ideal strategy. In the tropical paradise that is Sri Lanka, the possibilities are endless.

Another cost-beneficial method of relieving the monotony of monoculture, and creating greater faunal and floral diversity in tea, is crop diversification. Avocado, citrus varieties, coconut, cocoa, coffee, moringa, garcinia, pepper, clove, breadfruit, and jak are viable options, subject to suitability in terms of elevation, climate, ambient temperatures, and regional weather patterns. Some of these species would meet both high-shade and low-shade requirements as well. Despite the economic and biodiversity enrichment potential that is evident in this type of intercropping, it is a pity that neither in the company-owned sector, nor in the smallholder segment, are these models widely employed.

Another useful strategy would be the widespread application of Sloping Agricultural Land Technology (SALT) in tea, with sunflower plants, vetiver or lemongrass, along drain and bank edges. The first with its edible oil potential, and the latter two with their usefulness, both in perfumery and as insect repellents, carry other economic advantages as well.

Tea cultivation has both diminished and fragmented the original virgin forest cover, separating rich ecosystems, and trapping land-based fauna in steadily shrinking segments of isolated woodland. One method of restoring a degree of ecosystem balance would be to establish connecting jungle corridors through tea land, providing animals safe passage between separated forest patches. I am aware that one plantation company has meaningfully implemented this conservation strategy in one of its low-country tea plantations.



A couple of years ago, on an official visit to Hainan, a large island at the southern tip of mainland China, I was conducted through superb examples of multi-cropping on large, commercial scale rubber plantations. Rubber trees, strategically spaced, constituted the upper canopy, the middle level being either Cassia or fruit trees, whilst the ground cover consisted of an extraordinary variety of vegetables and medicinal herbs. This three-tiered cropping model is a fine example of the optimum, economically advantageous utilisation of agricultural land. Vietnam, Thailand, and India are other countries that have successfully replicated such models.

All the strategies described in this writing have been researched widely by specialists in the field, both in Sri Lanka and India, and the documented findings are easily available to anybody who may be interested.

Our plantation industry is a colonial heritage and as such legacies are, the world over, is not without its disagreeable features. It is not possible to rewrite history, but it is entirely within our means to reverse some of those less acceptable features and to moderate their impact in the future. Any strategy that we employ in mitigation would also be a contribution to the palliation of climate change, which is a process now well in motion. It is unstoppable, but the consequences can be minimised by intelligent and timely counteraction. It has to be done immediately, as tomorrow would be too late. 


(Anura Gunasekera is a member of the Wildlife and Nature Protection Society [WNPS], a retired plantation industry specialist, an amateur herpetologist, a keen bird-watcher, and a passionate conservationist. 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)