Climate Change Threatens Hydroelectricity, Tea Production – ADB

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Sri Lanka’s mountain ranges, home to some of Sri Lanka’s key agro crops led by tea, coupled with being the base for Sri Lanka’s hydroelectric generation, are at risk due to climate change, the Asian Development Bank (ADB) in a recent report warned.

Tea was Sri Lanka’s third largest foreign exchange earner last year, while hydroelectric generation from the principal hydroelectric reservoirs located in the country’s central hills, is Sri Lanka’s cheapest source of electricity.

The report titled ‘Climate Change Risk Profile of the Mountain Region in Sri Lanka’ and released on its website on 25 May 2022 further said Sri Lanka’s mountain area encompasses 15.1 per cent of the total land area of the island. GIS analysis of data from the Land Use Policy Planning Department showed that most of the mountain region is used for agriculture (267,925.6 hectares (ha)) or 27 per cent of its mountainous land mass.

The mountain region in Sri Lanka covers an area of 9,942 square kilometres or 15.2 per cent of the island’s total land area and has a climate ideal for forest growth, it further said. The mountain area spreads over into all provinces except the Northern Province. Sixteen of the country’s 25 districts are also associated with the mountain area. The mountain region covers 111 Divisional Secretariat Divisions (DSDs) and 3,409 Grama Niladhari Divisions (GNDs), the ADB said.

The study findings indicate potential disasters in the western and southwestern parts of the Central Highlands due to high rainfall conditions. In contrast, drought-related issues are projected in the north, east, and southeastern parts due to ‘climate change’ it warned.

The projected scenarios highlight three significant trends, which should be considered in developing climate change mitigation and adaptation strategies for implementation: An increase in the average annual rainfall in the whole mountain region, a prolonged and distinct dry season (compared to the current season), followed by excessive rain in a seasonal climate pattern and a distinct increase in ambient temperature.

GIS analysis of data from the Sustainable Energy Authority (SEA) showed there are 22 large-scale and 264 mini-hydropower stations in Sri Lanka—most are in the mountain region. Nineteen hydropower stations in the mountain region collectively generate 1,609.2 megawatts (MW) and 200 mini-hydropower facilities provide a total of 504 MW of electricity power.

Tea

Tea is the most significant and extensive plantation crop in the mountain region. Tea is grown on 151,419 ha of the total area. The country produced 278,900 metric tons of tea in 2020 (Central Bank of Sri Lanka 2021). Tea production is highly dependent on rainfall and temperature and production areas are categorised into three regions based on altitude. Low-grown tea is found at altitudes below 600 metres (m), covering 33,591 ha. Mid-grown tea is planted in areas at 600–1,200 m, covering 58,013 ha. High-grown tea is found in areas above 1,200 m, covering 59,815 ha.

Nuwara Eliya Tea District: A high plateau 1,868 m above sea level in a cool climate with a prevalent wet condition with moderate rainfall. This region has the highest average elevation. Combined with low temperatures, this area produces the most refined and sought-after tea varieties such as whole leaf Orange Pekoe and Broken Pekoe.

Dimbula Tea District: An area on the outskirts of NuwaraEliya and Horton Plains, at 1,100–1,600 m. This area lies in and around the Hatton Plateau and has southwestern rainfall and cool weather. Dimbula Region is further subdivided into eight sub districts, i.e., Hatton–Dickoya, Upcot–Maskeliya, Bogawanthalawa, Pathana–Kotagala, Lindula–Nanuoya–Thalawakele, Agrapathana, Pundalu Oya and Ramboda. Due to their high geographical variation and microclimates, a range of flavours are produced with a predominant golden-orange hue.

Kandy Tea District: Mid-grown tea is cultivated at an elevation of 650–1,300 m, although the major portion of this area is below 1,200 m. The district receives its main rainfall from the southwest monsoon. Most estates lie on the western slopes of the hillside and produce the best tea in the first quarter of the year when cool, dry weather sets in. Pusselawa–Hewaheta and Matale are the main sub districts.  Uda Pusselawa Tea District: Tea is grown at mid to high elevations of 950–1,600 m in a wedge between Nuwara Eliya and Uva areas, i.e., the eastern side of the Central Highlands. The main rainfall is from the northeast monsoon from November to January. Frequent misty conditions are prevalent in the region and dry, cool, windy conditions are experienced during the southwest monsoon. The two sub districts are Mathurata and Ragala-Halgran Oya.

Uva Tea District: Characterised by mid to high elevations from 914 m to 1,524 m with intermediate climate conditions. The main rainfall is received during the northeast monsoon with a dry spell after May. The eastern boundary of Sri Lanka’s tea-growing area is in this region. This tea, produced after a long dry spell, has a distinctly different taste from other Ceylon teas. The flavour and aroma are influenced by the reception of both northeast monsoon and southwest monsoon winds, which when traversing through the gulley and mountain slopes, shed their moisture on the lower slopes and carry dry winds to the higher elevations. The tea produced in this region is widely used for blends.

The sub districts in this region are Malwatte–Welimada, Demodara–Haliela–Badulla, Passara–Lunugala–Madolsima, Ella–Namunukula, Bandarawela–Punagala, Haputale, and Koslanda–Haldummulla.

Sabaragamuwa Tea District: Low-country tea is grown at an elevation of around 800 m, mostly by smallholders. Fast-growing bushes with long leaves are cultivated in this region. It has a warm climate with high rainfall and fertile soils. This region produces a large quantity of tea although only a small area falls within the mountain region.

Ruhuna Tea District: Low-country tea grown at elevations below 600 m, mainly in the southern lowland region of Sri Lanka. As in the case of Sabaragamuwa tea, a long leafed fast-growing bush is cultivated. The tea is a full-flavoured black tea with a strong aroma, distinct to the regions of Deniyaya, Matara, and Galle.

 Kandyan Home Gardens

Export crops are of great value due to their high market value. Among these export crops, cardamom, cloves, nutmeg, vanilla, coffee, cocoa, and pepper are grown mainly in the mountain region, with pepper, cinnamon, and coffee cultivated in small-scale plantations. Arecanut, betel, cinnamon, turmeric, and ginger are grown mainly in traditional home gardens in the mountain region known as Kandyan Home Gardens.

The Kandyan Home Garden is a traditional sustainable agricultural production system that is both ecologically and economically viable. It has a multi-strata vegetation structure and well-functioning ecological interactions, which conserve soil moisture, prevent erosion, and enhance pest control.

 The system contributes to household livelihoods.’Kandyan Home Gardens’ are usually found in Kandy, Kegalle, Kurunegala, Matale, Nuwara Eliya, Badulla and Ratnapura which are within the historic Kandyan Kingdom. As of 1995, Kandyan Home Gardens covered an area of approximately 858,100 ha. The essential characteristics and distribution of the main minor export crops in the mountain region  is  Cardamom, a highland crop grown above an elevation of 600 m.

It is cultivated in the Knuckles Region in Kandy and Matale Districts, the Dolosbage Hills of Kegalle District, the eastern side of the Pedro Hill Range in Nuwara Eliya District, and the foothills of Peak Wilderness of the Ratnapura District. It is also cultivated in the hilly areas of the wet zone and on a small-scale in the Rakwana Range. Three varieties of cardamom are grown in Sri Lanka: Malabar is grown in the lower elevations, while Mysore and Vazhukka are grown at elevations above 800 m. Cardamom is a shade-loving plant grown under canopy cover and requires well-drained loamy soil with high organic matter. A well-drained annual rainfall of 1,500–2,500 mm and temperatures between 10°C and 25°C are most favourable for growth, the ADB said.

Meanwhile, nutmeg flourishes in cooler climates and the mid-country areas of Sri Lanka are ideal for its growth. Sri Lanka grows nutmeg on 924 ha, 80 per cent of which is within Kandy District. Kegalle and Matale Districts are the other major areas for nutmeg cultivation.

 Nutmeg production requires a well-distributed annual rainfall of 1,500–2,500 mm and an average annual temperature between 20°C and 30°C. Nutmeg can grow at altitudes up to 1,500 m. Shade is an important factor during the first two years of growth, followed by exposure to light. A humid microclimate is also required for its establishment and fruit set. Persistent strong winds are harmful but sheltered valleys and leeward slopes are ideal for growing nutmeg.

 Cloves are cultivated on a total of 7,618 ha, mainly in Sri Lanka’s mid-country wet zone and in Kandy, Matale and Kegalle Districts. Deep, rich, well-drained loamy soil rich in humus are most suitable for growth. Cloves grow in a humid tropical climate up to 1,000-m elevation. The annual rainfall should be between 1,750 mm and 2,500 mm. However, flowering requires a dry period, which alternates with a moist one. The annual average temperature should be between 20°C and 30°C with less seasonal and diurnal variation.

 Cocoa grows mainly in mid-elevation mountain areas in Matale, Kandy, Badulla, and Monaragala Districts. Grown below an elevation of 600 m, cocoa is typically cultivated as a mixed crop in Kandyan Home Gardens or as an understory in rubber plantations. Well-drained soil with rich organic matter is important for cocoa. The ideal temperature range is from 21°C to 32°C with an annual rainfall of 1,150–2,500 mm. This crop prefers high levels of shade, humid conditions, and less windy conditions as humidity drops.

 Pepper grows in well-drained loamy soils rich in organic matter at an altitude ranging from sea level to 800 m. Annual rainfall should not be less than 1,750 mm. Prolonged droughts have a deleterious effect on pepper unless supplementary irrigation is provided. A clear dry spell, sufficient rainfall, and temperatures between 15°C and 35°C are required for flowering and pollination. Strong winds are harmful. Pepper is mainly cultivated in the drier parts of the mountain region, including Matale, Kandy, Ratnapura, and Badulla Districts.

Rubber is generally a lowland crop but has also been grown in the peripheral areas of the mountain region at lower altitudes of the wet and intermediate zones. The land conditions vary from entirely flat to undulating steep terrain. In the mountain region, rubber is cultivated along hill slopes at lower elevations on a total of 20,835 ha. Rubber is most productive on well-drained, steep to moderately undulating hilly areas, with an ideal annual Main Features and Characteristics of Sri Lanka’s Mountain Region 25 rainfall between 1,650 mm and 3,000 mm distributed evenly throughout the year. Annual rainfall of less than 1,250 mm is highly unfavourable.

 Rubber productivity severely declines if rainfall is less than 500 millimetres (mm) and is unevenly distributed over six months. Rainfall should occur ideally in the late evening, ceasing before the morning tapping. The ideal temperature should be between 23°C and 28°C. Temperatures below 20°C for more than a few weeks are unfavourable, the ADB publication said.

 Coconut is an invaluable resource, cultivated on 20 per cent of Sri Lanka’s arable land, of which 20 per cent are large-scale plantations and the rest owned by smallholders. Coconut is essentially a rain-fed crop that does not require irrigation but needs well-distributed rainfall throughout the year. The ideal conditions for coconut cultivation include sand-mixed soils in the lowlands, with soil moisture retained throughout the dry period.

 Coconut cultivation in the mountain region is restricted to the lower elevations in the wet and intermediate zones and is estimated at 5,952 ha in total, the ADB survey report said.

By Paneetha Ameresekere