Camellia sinensis – the tea plant’s official name – is used to make the second-most consumed liquid on Earth, after water, with 4.5-billion cups sipped every day. Fifty countries produce tea, creating an invaluable rural economy.
No country likes the beverage more than China. Tea is entwined in the culture of the world’s largest consumer and producer. In cities, people walk around with special cups filled with tea leaves. These are topped up with hot water so the tea percolates throughout the day.
A fifth-century proverb goes along the lines of: “Better to be deprived of food for three days than tea for one.” Growing it creates an economy for 80-million people in China, which produces about 40% of the global output of five million tonnes of tea every year.
But that tea culture is in trouble. Research from Tufts University in the United States, out this month, shows that climate change is disrupting tea’s growing season. A team from the university looked at rainfall figures between 1980 and 2011 to find how long the rain season normally lasts.
The research found that the critical monsoon season is now shorter, and ends later in the year. This is lowering yields in the tea-producing province of Yunnan and the 14 provinces around it.
For tea to be affected, the change has to be profound. Camellia sinensis is hardy. To grow it needs between 1 500mm and 2 000mm of rainfall a year, and for temperatures to hover between 20°C and 30°C.
This means tea is generally found in the tropics and below an altitude of 2 000m. At 35°C it starts to wilt. Frost is deadly. Heavy rainfall floods its fields and waters down the strength of the tea.
The Tufts researchers say the rate of climate change in southern China over the past six decades has been profound. Since 1950, rainfall has increased by 60mm a decade. Days with extreme heat – above 35°C – have also increased. This has adversely affected a range of crops.
“Changes in temperature and precipitation between 1981 and 2000 have resulted in declining yields of rice, wheat and maize across China,” the report says.
The future is likely to hold more of the same. The United Nations’ intergovernmental panel on climate change said in 2014 that the average surface temperatures in the country would increase by between 2°C and 5°C this century.
The most profound effect of the changing climate has been seen in the monsoon season. Farmers time their planting so they can harvest just after it heads off. Predictability was key. But in 2011, the monsoon season was 23 days shorter than in 1980. It now fades away in mid-September, meaning that farmers have to race against the arrival of frost to harvest a crop that is intricate to pick.
All this has lowered production, according to the Tufts researchers. For every 1% change in the date the monsoon abates, the average tea yield goes down by 0.5%.
“We find a consistent, negative association between tea yields and the monsoon retreat date,” the report said.
A 1% increase in daily rainfall decreases the yield by 0.3%, and a 1% decrease in radiation from the sun lowers yields by 0.9%. The tea also requires more labour to harvest because fields are waterlogged. And it fetches less on the market because it tastes weaker. For subsistence farmers producing a tonne of tea on a hectare, these shifts have meant that up to 50kg is being lost each year.
All this is cutting into the two cups a day the world’s two billion tea drinkers currently enjoy.
Tea around the world
Fifty countries produce tea globally. The effect of climate change therefore varies widely: some will no longer produce tea, while others will have bumper crops.
The United Nations’ Food and Agriculture Organisation predicts that this will balance out in the short term, and tea production will increase by 11% in the coming decade. But after 2025 production will decrease.
China and India – the world’s biggest tea producers and consumers – are facing waterlogged fields and lowered yields.
In Kenya, tea production is shifting north. In Sri Lanka, more floods and heavier rains will lower production of many well-known tea brands.
South Africa’s commercial rooibos tea – grown in a small part of the Western and Northern Cape – is faced with much less rainfall than needed and lower yields.
The biggest tea-selling companies, based in the United Kingdom, say the changing climate has altered the taste of tea. Black tea has apparently become weaker. At the same time, sales of green tea have increased. The future is therefore in the taste buds of consumers. – Sipho Kings
Hard times call for different flavours
The changing global climate has brought focus back to variants of tea that were previously ignored because others were more popular. Hardier variants are being selectively bred for the future.
In Sri Lanka, the spectre of flooding is being tackled by planting trees that can handle being waterlogged.
China has introduced schemes that focus on soil management techniques. These include building up and maintaining the organic matter in soil. This allows it to hold more water in the dry season, and filter out more water during floods.
The hardier wild variant of rooibos can survive the drought conditions predicted to prevail in its growing region. Changing to this variant means the local industry – producing 12 000 tonnes a year and employing 5 000 people – can survive the change.