Guwahati, July 6: A climate suitability map for tea has revealed that Cachar in south Assam will be the hardest hit by changes in temperature and floods.

The map, a long-term future scenario grid for tea from 2020 to 2100, has been prepared by the Jorhat-based Tea Research Association (TRA), using a global circulation model and regional circulation models.

The map and effects of climate change were revealed in the report of the working group on climate change of the Food and Agriculture Organisation's Inter-governmental Group on Tea at its 22nd meeting in Kenya from May 25 to 27.

The FAO for the first time brought out a booklet which outlines the climate change adaptation strategies of India, Kenya and Sri Lanka.

"It has been observed that temperature-wise, Cachar will be the most vulnerable while the rest of Assam will be moderately suitable, while precipitation-wise, the south bank of the Brahmaputra has more drought vulnerability and Cachar is the most flood-vulnerable," says the report authored by R.M. Bhagat, coordinator for the working group and deputy director of the tea association.

The rate of temperature increase will be faster post-2080. In 2020, the temperature will be suitable throughout the state.

The average annual maximum temperature has a decreasing trend till 2080. Post-2080, sharp increasing trends are observed, particularly in southern, middle and parts of Upper Assam. The annual temperature is likely to increase most in Cachar, where it may reach up to 36 degrees Celsius.

In the temperature range, 13 to 30 degrees Celsius has been taken as most suitable, 30 to 35 degrees as moderately suitable and beyond 35 degrees as vulnerable.

Areas with rainfall below 2,000mm are drought-vulnerable, while 2,000 to 4,000mm is suitable while rainfall more than 4,000mm can lead to floods.

There are 104 gardens in Cachar district and tea production in 2015-16 was 47.64 million kg, while in 2014-15 it was 49.03 million kg.

Tea being a rain-fed crop requires a certain type of soil and air temperature as well as moisture for growth.

"It is apprehended that increased temperature and decreased rainfall pattern observed in the region are undoubtedly going to affect the conditions posing a threat to the sustainability of the tea crop," the report says.

Tea bushes need adequate as well as distributed rainfall but heavy and erratic precipitation is responsible for damage to plantations in terms of soil erosion, lack of growth owing to less sunshine hours and different types of diseases, besides flooding.

Every year the Brahmaputra inundates a large area, which creates waterlogging in the productive tea growing areas in Assam.

Every year, about 15-20 per cent tea crop is damaged owing to waterlogging in tea plantations.

Erosion is another major concern and there are several tea gardens where a large area has been eroded.

"Over time, these changes are expected to have implications on tea, resulting in some traditional areas becoming unsuitable for cultivation. Producers will have to make considerable changes to their existing practices in order to continue to meet the global tea demand and quality requirements," the report says.

It adds that high-resolution models are required for better understanding of the vulnerability of tea-growing areas in the Northeast in future.