The world famous Darjeeling Tea is under threat due to unsteady temperatures and uncertain rainfall affecting the plantation production.
The maximum temperature in Kurseong has risen by 0.51 degree over the last 20 years while total annual rainfall dropped by 56 mm and relative humidity by 16.07 %, leading to a decline in overall production of Darjeeling tea in terms of green leaf production per hectare.
The West Bengal State Climate Action Plan has also expressed concern over “reduced productivity of Darjeeling tea due to increase in extended drought periods.”
Tea is a rain fed crop which needs specific soil and air temperature with proper moisture condition for required growth. Both increased temperatures and decreasing rainfall – along with change in relative humidity – adversely affect quantity and quality of tea plantation and production. With increase in temperature, the chances of infestation of pests also go up.
The perfect temperature for growing tea saplings is between 18°C and 30°C. The plant growth is adversely affected when the temperature goes above 32 degrees or drops below 13°C degrees. To add to the misery of tea plantation, strong winds, frequent frost, hail and excessive rainfall are also harmful for production of high quality tea.
“Both excess and shortage of water affect growth of tea bushes. Tea bushes need adequate and well distributed rainfall. Heavy and erratic rainfall can damage tea plantation due to soil erosion, lack of growth due to less sunshine hours and different types of insect pest and diseases, besides flooding,” explained Mrityunjay Choubey , researcher from DTR & DC, while speaking at a media workshop on climate change here last week.
Tea is grown in five different valleys in the region – Darjeeling, Mirik, Teesta, Rambang and Kurseong – each having different elevations and weather patterns.
“There is no doubt that rainfall has come down drastically in all the valleys. But we have to collate data from all the stations, including those run by the India Meteorological Department and also analyse other factors such as shift from inorganic to organic farming and levels of absenteeism, before we can pinpoint reasons for falling production. Climate change may be one of the factors,” pointed out Prahalad Chetri, project director of the R&D centre, Tea Board of India.
Choubey, however, said that since the experimental farm followed the inorganic method of cultivation, yield reduction could not be attributed to shift from inorganic to organic cultivation practices. “The probable reason (for yield reduction) may be temperature rise, lack of total as well as distribution of rainfall and less humidity. These factors affect carbohydrate assimilation, respiration and evapo-transpiration of tea plants, pest and disease infestation, drought and heavy rainfall incidence and soil degradation,” he added.
In view of this, he said, it was critical to identify and evaluate options for adaptation to future climate change. Adaptation measures will include use of drought-tolerant clones, reducing chemical load by integrated nutrient management. Organic farming is highly adaptable to climate change as it preserves inherent soil fertility and maintains organic matter in soils which can sustain productivity in the event of drought or irregular rainfall.