Tea cultivation under changing climatic conditions

Full text

Global tea science
Current status and future needs
Edited by Dr V. S. Sharma, formerly UPASI Tea Research
Institute, India
Dr M. T. Kumudini Gunasekare, formerly Tea Research
Institute, Sri Lanka
BURLEIGH DODDS SERIES IN AGRICULTURAL SCIENCE
E-CHAPTER FROM THIS BOOK

http://dx.doi.org/10.19103/AS.2017.0036.19
© Burleigh Dodds Science Publishing Limited, 2018. All rights reserved.
Tea cultivation under changing
climatic conditions
Wenyan Han, Xin Li, Peng Yan, Liping Zhang and Golam Jalal Ahammed, Tea Research
Institute of the Chinese Academy of Agricultural Sciences (TRI, CAAS), China
1 Introduction
2 Climate change and climatic variability
3 Effects of climate change on the suitability of tea planting areas and plucking
duration
4 Effects of climate change on tea production
5 Effects of climate change on tea quality
6 Adaptation and mitigation strategies
7 Conclusion
8 Where to look for further information
9 Acknowledgements
10 References
1 Introduction
Intense human activity over the last two centuries has resulted in a rapid global climate change.
The Intergovernmental Panel on Climate Change (IPCC) reported that the concentrations of
the main greenhouse gases CO2, CH4 and N2O have reached 393.1 ppm, 1819 ppb and
325.1 ppb in 2012, increasing by 41%, 160% and 20%, respectively, compared to the pre-
industrial era (IPCC, 2013). As a result, the speed of global warming has increased and the
global mean surface temperature has increased by 0.85°C over the period 1880–2012. The
world meteorological organisation confirmed the continuation of this warming trend over
the past few decades, with the five-year period from 2011 to 2015 being the warmest on
record globally, and 2015 being the warmest year on record to date (WMO, 2016).
Despite the increase in the mean temperature, many extreme weather events, including
the breaking of temperature records, heavy precipitation and prolonged intense hot,
dry seasons, occur. As a result, droughts, floods, storms, landslides, outbreaks of pests
and diseases and a loss of diversity are now frequently experienced. For example, the
probability of extreme high temperatures increased by a factor of 10 or more in some
locations during the period 2011–15 (WMO, 2016).
Chapter taken from: Sharma, V. S. and Gunasekare, M. T. K. (ed.), Global tea science: Current status and future needs, Burleigh Dodds
Science Publishing, Cambridge, UK, 2018, (ISBN: ISBN: 978 1 78676 160 6; www.bdspublishing.com)

Tea cultivation under changing climatic conditions
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Tea is one of the most important cash crops worldwide, playing a significant role in rural
development, poverty reduction and food security in developing countries. It is planted
in 58 countries in the five continents, the majority being in Asia and Africa. The total area
of land under tea cultivation is 4.37 million ha, with an annual production of 5.30 million
tons in 2015 (ITC, 2016). Smallholders are the main force in tea production, especially
in the mountainous regions. It was estimated that China and India have 20 million and
three million rural labourers, respectively, involved in tea production and processing.
Smallholders constitute 73%, 60% and 47% of the total tea production in Sri Lanka, Kenya
and Indonesia, respectively. Tea also plays a vital role in relation to economic development.
For example, in Sri Lanka, it generates 1.3 billion US dollars in exports, comprising 14.84%
of the total export earnings or 59.72% of the agricultural export earnings. Tea exports
contributed 20% to the total national foreign exchange earnings in Kenya (Azapagic et
al., 2016).
As it is a rain-fed mono-cropping system, tea cultivation depends on weather conditions
for optimal growth. Global climate change, therefore, has a great impact on tea growth
and development. Ochieng et al. (2016) found that tea would be one of the crops most
adversely affected by climate change. Increasing temperatures and extreme weather
events are posing a significant threat to the resilience of tea production systems. There is,
therefore, an urgent need to develop mitigation and adaptation strategies to cope with
climate change. We have attempted to review recent research modelling and the potential
impact of climate change on tea cultivation. An attempt is also made to suggest strategies
for mitigating its adverse influence on abiotic stress and temperature fluctuation in order
to reduce the risks presented by climate change and to promote sustainable development
of tea industry.
2 Climate change and climatic variability
2.1 The extent of climate change
It has been established that the global mean surface temperature has increased since the
late nineteenth century. Each of the past three decades has been successively warmer at
the Earth’s surface than any of the previous decades in the instrumental record. Globally
averaged combined land and ocean temperature data as calculated by a linear trend show
a warming of 0.85°C over the period 1880–2012 (IPCC, 2013).
As with many other regions of the world, the major tea-producing countries such
as China, India, Sri Lanka and Kenya have witnessed a significant change in climate in
the last few decades. Han et al. (2016) evaluated climate change in representative tea-
producing cities at various latitudes in China, including Haikou, Kunming, Hangzhou
and Jinan. The results showed that the annual mean temperature and extreme lowest
temperature have increased by 1.0–1.6°C and 2.1–3.8°C, respectively, over the last 50
years. The highest temperature was not significantly different, but the number of hot days
having a temperature >35°C had significantly increased, particularly in Hangzhou city.
The annual precipitation did not show a discernible fluctuation. However, the number of
rainy days (>0.1 mm) and the atmospheric relative humidity have fallen by 6.7–13.2 d and
3.3–9.4%, respectively, over the same period. Similarly, the annual hours of sunshine and
its percentage decreased from 207.1 h and 56.3% in 1950 to 158.0 h and 42.9% in 2010,
respectively.

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Tea cultivation under changing climatic conditions 3
The main tea-growing areas of northeast India, Assam and West Bengal, showed a
steady increase in mean temperature with the average minimum temperature having
increased by about 1.3°C over the last 100 years. However, the annual precipitation has
steadily declined. For example, annual precipitation in the South bank region at the TTRI
of Assam has declined by more than 200 mm in the last 96 years (Bhagat et al., 2016).
Similarly, Kenya, a tropical tea-producing country, also showed an increase in temperature
and a decline in rainfall over the last few decades, with mean temperature increase of
0.1°C and a decrease in rainfall of 153 mm in Kericho over the last 54 years (Bore and
Nyabundi, 2016). In Sri Lanka, temperatures have increased markedly over the last one
and a half centuries and the warming rate has accelerated in recent years. For example,
the mean temperature increased at a rate of 0.016°C per year during the period 1961–90
and 0.025°C per year during the period 1987–96 (Esham and Garforth, 2013).
In terms of future climate, global surface temperature change for the end of the
twenty-first century is likely to exceed 1.5°C relative to 1850–1900, and warming will
continue beyond 2100 (IPCC, 2013). In terms of tea-producing regions, Dutta (2014)
applied predicted models derived by WorldClim and IPCC4 and found that the average
temperature may increase by 2°C in Northeast India in 2050, while there will be a little
variation in the rainfall pattern as compared to today. The mean temperature in Sri Lanka
is predicted to increase by 2.4°C by the end of the century (Basnayake, 2011), and the
minimum and maximum mean temperatures are predicted to increase between the ranges
of 0.5–0.7°C and 0.6–0.9°C, respectively, by 2050 (Esham and Garforth, 2013). The mean
air temperature in East Africa is predicted to increase by about 2.5°C by 2025 and 3.4°C
by 2075, while rainfall is predicted to increase by about 2% by 2025 and 11% by 2075
(Bore and Nyabundi, 2016).
A gradual increase in global-scale precipitation is projected in the twenty-first
century, but the changes in response to warming will not be uniform, with some regions
experiencing increases, and others experiencing decreases or little change. High-latitude
land masses are likely to experience greater amounts of precipitation due to the additional
water carrying capacity of the warmer troposphere. Many midlatitude and subtropical arid
and semi-arid regions are likely to experience less precipitation (IPCC, 2013).
2.2 Extreme weather events
As temperatures increase, many extreme weather and climate events have been observed
since around 1950, and future increases in long-term droughts and precipitation extremes
are very likely in Africa, East Asia, South Asia and Southeast Asia (IPCC, 2013) – the main
tea-producing regions of the world. For example, on the global scale, there has been a
decrease in the number of cold days and nights and an increase in the number of warm
days and nights, while the number of heavy precipitation events over land has increased
in more regions than it has decreased. The world meteorological organisation not only
recorded the warmest year in 2015, but found large numbers of extreme weather and
climate events, including heat and cold waves, tropical cyclones, flooding, droughts and
severe storms during the period 2011–15 (WMO, 2016).
In tea-growing areas, Han et al. (2016) reported that the frequency of climate
variations and extreme weather events, such as drought, high daily precipitation and
late spring cold spells, had increased significantly in China in recent years. In Kenya,
extreme weather events were characterised by a rising trend of hail and an increasing
incidence of frost and heavy rainfall over a short period, followed by prolonged

Tea cultivation under changing climatic conditions
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dry periods (Bore and Nyabundi, 2016). Tea farmers ranked recurrent droughts and
changes in rainfall patterns as the most important indicators of climate change in
Kenya (Mwendwa and Giliba, 2012).
3 Effects of climate change on the suitability of tea
planting areas and plucking duration
3.1 Basic environmental requirements for tea growth and
development
Tea originated in southwestern China, at the centre of the Yunnan and Guizhou plateaus,
a junction of tropical and subtropical areas. This region is characterised by a warm climate,
abundant rainfall, high humidity and sufficiently diffused light. Under such conditions, tea
plants have gradually evolved specific characteristics of adaptation to warm, moist weather,
diffused light and acidic soils. The basic environmental requirements for tea growth and
development are listed in Table 1. Pronounced changes in temperature, precipitation,
relative humidity, rainy days and annual sunlight hours will not only directly affect tea
yield and quality, but will also change other basic parameters necessary for its growth
and development, such as soil pH, water content, organic matter, nutrient availability,
pest and disease management, ecological systems around tea gardens and eventually
tea processing. Tea is one of the tree species most affected by changes in bio-climatic
suitability in Yunnan province, China (Ranjitkar et al., 2016).
3.2 Shift of tea production areas
With increasing temperatures, especially a rise in the minimum temperature, the tea-
growing area would be extended to higher latitudes and higher altitude ecosystems. This
might be beneficial for tea production in relatively cold climate regions such as highland and
subtropical areas, but would have a negative effect in lowland and tropical areas. Therefore,
those growing regions which are currently well known may become unsuitable for tea
cultivation in the future. This could trigger a shift in suitable locations for the cultivation of
Table 1 Basic environmental requirements for tea growth and development
Climate parameter Extreme lowest Normal range Optimum
Temperature (°C) −20 (var. sinensis),
−8 (var. assamica)
13–26 18–23
Annual accumulated
temperature (≥10°C)
3000 4000–8000 6000–7000
Annual precipitation (mm) 500 800–2500 1500–2000
Annual relative humidity (%) 60 70–90 80–85
Soil moisture (% of water
holding capacity)
50 60–95 70–90
Soil pH (in water suspension) 3.0 3.5–6.5 4.5–5.5

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Tea cultivation under changing climatic conditions 5
some varieties if high-quality tea is to be obtained. For example, in the Uji area of Kyoto,
one of the oldest and most famous green-tea-producing areas in Japan, tea quality has been
gradually affected by climate change (Ashardiono and Cassim, 2014). In China, the main tea-
producing area could gradually shift from south to north. The area under tea cultivation in
the South Tea District (Hainan, Guangdong, Guangxi, Fujian and Taiwan provinces) totalled
371.8 thousand ha in 2014, a 59.8% increase compared to that of 1983. Meanwhile, the
tea area in the North Tea District in China (Shandong, Shanxi, Gansu, Henan and Hubei
provinces) was 618.6 thousand ha in 2014, a seven-fold increase over 1983. However, the
northern boundary of tea-producing areas in China is unlikely to move further north beyond
Qing Ridge and the Wai River due to limited precipitation and higher soil pH in the northern
part of this region. In Kenya, the optimum tea-producing zone is expected to shift to a
higher altitude of between 2000 and 2300 m by 2050, compared with the current altitude of
between 1500 and 2100 m. By 2050, the tea areas at altitudes between 1400 and 2000 m
will suffer the greatest decrease in suitability and the areas around 2300 m will have the
highest increase in suitability when compared to the present day.
Overall, the suitability of tea-growing areas is expected to decline by 22.5% by 2075
(Bore and Nyabundi, 2016). Suitable areas will shift up the altitudinal gradient: those
retaining some suitability will see decreases of between 20 and 40%, compared with
today’s suitability of 60–80% in Uganda (Eitzinger et al., 2011). In Eastern Africa, up to
40% yield loss is expected due to the reduction in suitable areas caused by temperature
increase (Adhikari et al., 2015). Due to differing sensitivity to temperature increases, the
reduced suitable area for Camellia sinensis var sinensis was greater than that for Camellia
sinensis var assamica in the Yunnan province of China (Ranjitkar et al., 2016).
3.3 Tea plucking duration
The temperature increase in subtropical areas with distinct seasons will extend the duration
of growing and plucking. It is reported that the number of days warmer than 10°C, which is
regarded as the starting temperature for tea sprouting, may increase by 15 d if the annual
mean temperature increases by 1°C (Yang, 2006). With an increase in spring temperatures, the
tea budding time will be advanced and the harvest can begin earlier. Lou et al. (2015) found
that the plucking date of the Longjing-43 tea cultivar in China was significantly advanced
by 0.88–1.28 d/decade, based on phenological and economic output models established
using meteorological data from 1972 to 2013. In addition, Lou et al. found that the amount
of high-quality tea decreased significantly. However, economic output depended on the
scale of the farm. In tea plantations, the economic output could be reduced due to difficulty
in employing sufficient pluckers for high-quality tea, while smallholders experienced no
significant decline in profits (Lou et al., 2015). Early plucking of spring tea would increase the
yield, but would probably pose a risk of more extreme weather events, such as later spring
coldness. In Sri Lanka, the delayed onset of the monsoon not only reduced tea production,
but also shortened the cultivation season (Esham and Garforth, 2013).
4 Effects of climate change on tea production
Climate change brings both advantages and disadvantages for the growth and development
of tea and will ultimately have a considerable impact on production. The beneficial changes

Tea cultivation under changing climatic conditions
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include increases in temperature and CO2. The adverse impacts include a decrease in rainy
days and in relative humidity, and an increase in climate extremes and variations, such as
drought, flood and extremely cold and hot weather. These adverse climate changes will
cause serious problems for tea production and sustainable development. The impact of
the reduction of sunny days will depend on the degree of change and the location.
4.1 Modelling and temperature
Econometric modelling is normally used to assess the effect of climate change on crop
yields. Hsiang (2016) provides overviews of the methods used. Normally, regression models
are estimated using panel data sets of crop yield. Duncan et al. (2016) used a garden-
level panel data set and estimated statistical models in Assam, India, to identify the causal
effect of monthly temperature, monthly precipitation, drought intensity and precipitation
variability on tea yield and found that monthly temperatures above 26.6°C had a negative
effect on yield. An extra one degree of warming at an average monthly temperature of 28°C
would result in a 3.8% reduction in yield. Wijeratne (1996) and Challinor et al. (2007) also
found that yield tended to decline with increasing temperature in higher mean temperature
regions (>25–26°C). But in a region or season with low temperatures, an increase in
temperature would increase yield. For example, the mean temperature in Lushan Mountain
at an altitude of 1020 m in April was 13.8°C and the yield was only 74.8% of that at an
altitude of 212 m and a mean temperature of 17.6°C (Han et al., 2017).
4.2 Rainfall or monsoon
Boehm et al. (2016) analysed the effect of monsoon dynamics and weather on tea
production by using provincial-level data of tea production in China and found yield to
be more sensitive to precipitation than to temperature. An increase in the retreat date of
the monsoon and an increase in monsoon precipitation are associated with a decrease in
tea yield. IPCC (2013) predicts that global measures of monsoon by the area and summer
precipitation are likely to increase in the twenty-first century, as the monsoon circulation
weakens. The monsoon season is predicted to be longer with an earlier arrival and a
similar or later retreat date. The increase in seasonal mean precipitation is likely to be most
pronounced in the East and South Asian summer monsoons, while the change in other
monsoon regions is subject to greater uncertainty (IPCC, 2013).
Changes in the monsoon season will affect tea production because the quantity and
variability of rainfall are crucial. The effects of precipitation relative to temperature are
even more important in tropical countries such as Kenya and Sri Lanka (Bore et al., 2013;
Esham and Garforth, 2013). Diminishing rainfall reduces tea yields, but this depends on
its distribution over time. During long rains, tea production is lower when compared with
short rains. This is due to long rainy periods reducing sunshine and the photosynthesis of
tea leaves. Extreme rainfall events such as floods and droughts will also negatively affect
tea yield (Esham and Garforth, 2013; Duncan et al., 2016). Wijeratne et al. (2007) found
that a reduction of monthly rainfall by 100 mm could reduce productivity of made tea by
30–80 kg/ha/month in Sri Lanka.
The reduction in annual rainy days (even with the same quantity of precipitation)
and relative humidity, which are closely correlated, will adversely affect tea production.
For example, in Jinan city in China, the mean annual rainy days, precipitation and
relative humidity were only 75 d, 689 mm and 58%, respectively, over the last 60 years.

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Tea cultivation under changing climatic conditions 7
A further reduction in these parameters will certainly reduce tea growth and production.
Furthermore, the rise in temperature will increase soil evaporation and plant transpiration,
causing water shortage or seasonal drought in areas with low precipitation. Soil water
deficits showed a negative correlation with tea yields (Bore et al., 2013), and higher water
availability increased the growth of new leaves (Ahmed et al., 2014). The highest tea
leaf production per hectare depends on 4000–4600 mm annual rainfall, according to an
analysis of field experiment results with weather data in Bangladesh (Ali et al., 2014).
Tea generally exhibits a positive interaction between rainfall and temperature because its
production depends on stable temperatures and consistent rainfall patterns (Ochieng et
al., 2016). Any significant change in temperature and precipitation will affect production.
4.3 CO2 concentration
The increase in CO2 concentration could improve photosynthesis in tea plants. Jiang et al.
(2005) found that CO2 concentrations of 550 or 750 µmol/mol increased the net photosynthesis
of tea shoots by 17.9% and 25.8%, respectively, compared to ambient air CO2 concentration.
An increase in CO2 concentration also resulted in the reduction or disappearance of midday
depression. Our research showed that plant height, fresh shoot weight and root weight of tea
seedlings were 63.2 cm, 9.6 g and 9.9 g at 800 µmol/mol CO2, which increased by 13.5%, 24.7%
and 67.8%, respectively, compared to that under the ambient CO2 concentration of 380 µmol/
mol (Table 2) (Li et al., 2017). CO2 enrichment also promoted photosynthesis and respiration
in tea plants. However, the photosynthesis would acclimatise to high CO2 concentration, so
that the increase in yield would not be as great as expected since CO2 concentration increases
gradually with long-term climatic change. In addition, as the concentration of CO2 increases,
other plant growth limiting factors such as a shortage of nitrogen and microelements will
appear, further reducing the benefit of the CO2 concentration increment to tea yield. However,
this could be overcome by proper nutrient management.
4.4 Pests and diseases
The incidence and proliferation of pests, diseases and weeds will increase with climate
change (Lal, 2005). Warmer weather helps insects and pathogens to survive in winter,
which is a critical time for their reduction, and thus helps to shorten the damaging period
by increasing the number of annual generations and reproduction rates in some pests. For
example, the tea geometrid (Ectropis obliqua) has six generations per year in Hangzhou
under normal weather conditions. However, this will increase to seven generations if the
mean temperature rises above 20°C during October (Wang and Jin, 2010). The numbers
of over-wintering tea green leafhoppers and their reproductive rate are significantly
correlated with the number of days with a daily mean temperature above 0°C in Hangzhou
Table 2 Effect of CO2 enrichment on the growth of the tea plant
Treatment Height (cm)
Fresh shoot weight
(g)
Fresh root weight
(g) Root/shoot ratio
Ambient CO255.7 ± 3.73b7.7 ± 0.98b5.9 ± 0.74b0.47 ± 0.031a
Elevated CO263.2 ± 4.65a9.6 ± 1.47a9.9 ± 1.32a0.60 ± 0.064b
Different letters in the same column denote significant statistical difference (P < 0.05).

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district (Yang, 2005). The higher temperature, together with lower relative humidity, also
favours some pests. The incidence of diseases is positively correlated to temperature and
negatively correlated to sunlight hours (Li et al., 2010). For example, the incidence of
Phomopsis canker disease in southern Indian tea plantations was significantly related to
local climate (Ponmurugan et al., 2013). Thrips (Scirtothrips dorsalis Hood) and the tea
green leafhopper (Empoasca flavescens Fabricius), which were previously considered as
minor or occasionally serious pests in localised areas of tea plantations, are now established
as regular, and at times major pests in the tea plantations of North Bengal, spread over the
sub-Himalayan slopes and the adjoining plains of Terai and the Dooars (Saha et al., 2012).
Our recent investigation also showed that the leaf disease ‘blister blight’ (Exobasidium
vexans Massee), which normally occurs in tropical Yunnan and Hainan Provinces, has
become a problem in Songyang and Pujian Counties of Zhejiang Province, the typical
subtropical zone. The incidence of anthracnose disease (Colletotrichum gloeosporioides)
also increased significantly with elevated CO2 concentrations which reduces the
endogenous caffeine content of tea leaves (Li et al., 2016). Pest activities, tea plant and
pest interactions could be changed due to altered plant physiology and/or morphology
under increased CO2 concentration (Chakraborty et al., 2000). Due to the increasing
incidence and activities of pests and diseases, the average yield could be reduced by up
to 40% if no proper measures were taken (Oerke et al., 1996).
4.5 Soil quality
An increase in temperature speeds up the microbe depletion of soil organic matter while
reducing the time needed to release nutrients from chemical fertilisers.
Intense daily precipitation may cause severe flooding or landslides, which remove fertile
top soils. The enrichment of CO2 and other air pollutants such as SO2 and NO2 will cause
strong acid precipitation that further increases soil acidity. It should be noted that tea soils
in China are already too acidic, one-third being below pH 4.5 (Han et al., 2002). Further
acidification will therefore degrade soil quality and tea production.
4.6 Solar radiation
A reduction in sunlight hours resulting from fewer rainy days and more cloudy days
with diffused light would be beneficial for tea growth and development in tropical or
subtropical areas currently receiving intense solar radiation. However, it would be harmful
for cultivation in high mountains or ecosystems with low solar radiation. Boehm et al.
(2016) found that a 1% decrease in solar radiation in the previous growing season was
associated with 0.554–0.864% decrease in tea yields.
4.7 Extreme climate events
Climate extremes and variations, such as drought, flood and very cold or hot weather, will
cause serious problems for tea production and sustainable development. Because of its
unpredictable nature, it would be the most significant factor influencing year-to-year tea
production. Ahmed et al. (2014) found that the tea growth during the spring drought in
Yunnan Province is 50% lower than that compared to the monsoon period. The previous
year’s weather factors had a significant impact on tea yields (Boehm et al., 2016), heat
stress causing obvious alterations in the leaf phenotype and significantly decreasing the
net photosynthetic rate and tea yield (Li et al., 2015).

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Tea cultivation under changing climatic conditions 9
5 Effects of climate change on tea quality
The most commonly used tea quality parameters include free amino acids, polyphenols or
catechins, caffeine and water-extracted substances. With a certain polyphenol concentration,
higher levels of free amino acids give better green tea quality. Polyphenols or catechins are
precursors to the theaflavins and thearubigins developed in black tea processing, so higher
levels of polyphenols, to some extent, deliver better black tea quality. The amino acids and
polyphenols in tea shoots are mainly a result of nitrogen and carbon metabolisms and their
balance in tea plants, which are significantly affected by climate change.
5.1 Temperature and rainfall
Relatively low temperatures are beneficial to nitrogen metabolism, especially the bio-synthesis
of amino acids. High temperatures have a positive impact on carbon metabolism and the bio-
synthesis of polyphenols. The mean temperature 15 d before tea plucking has a significant
negative correlation with amino acids, although it is positively correlated with polyphenols
(Huang, 1985). For example, epigallocatechin (EGC), epicatechin (EC), epicatechin gallate
(ECG) and epigallocatechin gallate (EGCG) increased with a rise in the daily average
temperature. Long periods of precipitation led to the decline in EGC, EC, ECG, EGCG and
their total catechins content but increased C (catechin) content (Wang et al., 2011).
The relative humidity of a tea-growing location is decided by water availability and
temperature. The amount of sunlight hours is related to the intensity of solar radiation and
affects temperature. Amino acid concentrations in tea shoots are positively correlated with
relative humidity and negatively correlated with sunlight hours. However, tea polyphenols
show just the opposite trend, which is a negative correlation with relative humidity and a
positive correlation with sunlight hours (Huang, 1985; Wei et al., 2011).
The majority of famous Chinese teas are typically produced in mountainous regions
and near rivers or lakes. Mountainous tea-growing regions are characterised by altitudes
between 300 and 1000 m, higher precipitation and higher relative humidity, more diffused
light, lower temperature and higher diurnal temperature variation compared to low lands
(Wang and Jin, 2010). These are favourable weather conditions under which tea plants
synthesise and accumulate amino acids and other nitrogen-bearing quality components.
Our research also showed that with the increasing altitude of cultivation, amino acids
increased and polyphenols decreased, resulting in a lower ratio of tea polyphenols to
amino acids (Table 3) (Han et al., 2017).
Further studies show that among the amino acids, the concentration of theanine,
glutamic acid, arginine, serine, γ-aminobutyric acid and aspartic acid increased significantly
with increasing elevational gradients. However, epigallocatechin-3-gallate (EGCG) and
ECG significantly decreased under these conditions, indicating that catechin galloylation
was inhibited at lower temperatures (Han et al., 2017). Tea-growing regions near lakes or
rivers also have a high relative humidity, more cloudy days and diffused light and relatively
stable temperatures. Such weather conditions also help in nitrogen metabolism and the
bio-synthesis of amino acids.
Water availability will affect tea quality through a change of individual secondary
metabolites. In a greenhouse experiment, higher water availability significantly
increased total methylxanthine and phenolic concentrations in tea leaves, but decreased
concentrations of EGCG (Ahmed et al., 2013). However, a field study on the effects of
monsoon rains on tea showed that too much water brings the opposite result. Ahmed et

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al. (2014) compared quality of tea sampled from the spring drought and after the onset
of the East Asian Monsoon in the Yunnan Province of China. The results showed that
concentrations of catechin and methylxanthine secondary metabolites, major compounds
which determine tea functional quality, were up to 50% lower during the monsoon, while
total phenolic concentrations and antioxidant activity increased.
5.2 CO2 concentration
An elevated CO2 level exerts a significant impact on tea quality. A growth chamber study
showed that elevated CO2 at 500 and 700 µmol/mol decreased tea amino acids by
1.7–4.5% and 6.7–12.2%, respectively, when compared to the current ambient air CO2
concentration. At the same time, the caffeine content was also reduced by 3.1–4.6% and
5.1–10.7%, respectively. However, polyphenol concentrations increased by 3.8–6.0% and
6.9–11.3%, respectively. The soluble saccharide content increased by 8.4–14.4% and
18.1–28.2%, respectively (Jiang et al., 2006).
From the above evaluation, it may be seen that global warming will probably reduce green
tea quality, while to some extent increasing that of black tea. Of course, an inappropriate
ratio of polyphenols to free amino acids in shoots will also cause a deterioration in black
tea quality.
Other climate variations and extremes such as late spring cold spells, frost, hail, flooding
and drought will not only damage the growth and development of tea plants, but will
also lead to deterioration in tea quality. Climate variations and extremes also resulted in
biodiversity loss in tea-growing areas (Mwendwa and Giliba, 2012), which could cause
pest and disease outbreaks and increase pesticide residue in tea products.
6 Adaptation and mitigation strategies
Planning for climate change adaptation and mitigation initiatives is essential, not only
for dealing with the negative impacts of climate change, but also in order to create cost-
effective opportunities and benefits for sustainable development of the tea industry. These
strategies should have at least three levels: government policy, technology and technical
development and community involvement for the extension of adaptation and mitigation
measures. These should be integrated for the best outcomes.
Table 3 Tea polyphenols, free amino acid contents and their ratios in green tea as influenced by
changes in cultivation altitude
Sampling site Elevation (m)
Total polyphenols
(TP, mg/g)
Free amino acids
(AA, mg/g) TP/AA ratio
Cumaling 212 245.2 ± 4.7a26.1 ± 2.7d9.5 ± 1.2a
Mazu temple 420 242.0 ± 7.2a29.2 ± 2.0cd 8.3 ± 0.8a
Songshuling 574 200.8 ± 4.8b35.2 ± 2.0b5.7 ± 0.4b
Xiaotianchi 828 199.0 ± 5.2b33.3 ± 3.1bc 6.0 ± 0.7b
Jingzuo
station
1020 167.3 ± 18.4c43.1 ± 2.3a3.9 ± 0.3c
Means denoted by different letters in the same column are significantly different (P < 0.05).

© Burleigh Dodds Science Publishing Limited, 2018. All rights reserved.
Tea cultivation under changing climatic conditions 11
6.1 Governmental policies and strategies
Climate change is often referred to as a global problem, requiring top-down international
and national strategies to achieve substantial climate change adaptation and mitigation.
For example, individuals are unlikely to take responsibility for the global accumulation
of atmospheric greenhouse gases. Therefore, effectively integrated and coordinated
government policies or strategies are required for cost-effectiveness and consistency of
implementation.
Establishing international and national networks on climate
change
International and national networks involving international and interdisciplinary research and
communication units can be initiated based on coordinated policies or/and strategies to
advance research collaboration on impact assessments of climate change. Such networks will
help to set up policies through integrating the natural, social and cultural aspects of climate
change. The Climate Change working group in the FAO Intergovernmental Group on Tea
should be strengthened to collect and collate the available research data to determine the
impact of climate change on the tea economy, to identify/suggest mitigation and adaptation
strategies and to develop appropriate long-term technologies. Collaborative research
networks with a focus on climate change should be established at international and national
levels. For example, a national legal framework capable of managing water resources in
accordance with anticipated climate change impacts should be built for adjusting water
allocations and improving usage efficiency. Extension networks to implement mitigation and
adaptation measures at different governmental levels should be initiated.
Strengthening investment in field infrastructure
Infrastructure construction and improvement, such as drainage and irrigation systems, road
construction, ecosystem diversity and rebalancing should be strengthened. Infrastructure
is considered a very good investment from the cost–benefit analysis point of view, even
in the absence of climate change. Taking into account the high cost across the board to
individual’ tea plantations, governments should play a key role in this area.
Promoting organic, good agricultural practices (GAP) and climate-
smart tea production
Organic farming is seen as a system capable of contributing to climate mitigation and
sustainable agriculture. Recent research shows that organically managed tea agro-
ecosystems can enhance soil carbon sequestration through increasing soil organic matter
(carbon) levels (Han et al., 2013a; Subramanian et al., 2013). Organic tea soils also have
statistically significant higher levels of soil pH, total nitrogen content and soil microbial
biomass, carbon (C), nitrogen (N) and phosphorus (P) and their ratios to total organic C,
N and P, respectively (Han et al., 2013a). This translates into better plant nutrient content,
increased water retention capacity and better soil structure and thus to higher yields and
greater soil resilience (FAO, 2009).
Organically managed tea systems are further associated with higher levels of biodiversity,
including natural predators for pest control (Li et al., 2014; Saikia et al., 2014; Liu et al.,

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2015). Pest and disease damages and the imbalance of nutrients, especially shortages of
nitrogen, will decrease tea yields by 20–30%. However, organic tea has a 20–50% higher
price compared to conventional tea, compensating for the loss in yield. Promoting organic
tea production is therefore not only beneficial to farmers’ incomes, but offers significant
scope for climate change adaptation.
GAP and/or green farming consists of a collection of principles which take into account
economic, social and environmental sustainability. These apply to on-farm production and
post-production processes for safe and healthy food and non-food agricultural products.
They also apply to integrated pest management, integrated plant nutrient management
and conservation agriculture, which are beneficial techniques for mitigation and adaption
to climate change.
Climate-smart agriculture is an approach which helps to guide the transformation
and reorientation of agricultural systems to effectively support development and ensure
food security in a changing climate. It aims to tackle three main objectives: a sustainable
increase in agricultural productivity and incomes, adaptation and the building of resilience
to climate change and the seeking of opportunities to reduce greenhouse gas emissions
and increase carbon sequestration.
Precision agriculture is a high-tech farming system. It uses global positioning systems,
geographical information systems and remote sensing to collect the spatial variability
of parameters related to crop yield and quality, such as plant-growing situations, terrain
features, soil organic matter, moisture and nitrogen contents and pH. It utilises agricultural
inputs by machines and equipment controlled by the Expert Technology System. Precision
agriculture is an effective and efficient way of combating climate change, offering
considerable savings in natural resources and optimising crop yield and quality.
6.2 Research and development priorities for new and improved
technologies
Traditional coping mechanisms will not always be adequate for dealing with the expected
medium- and long-term impacts of climate change. Innovative agricultural technologies
and practices can play a significant role in mitigation of and adaptation to climate
change, especially in developing countries where agricultural productivity is low, while
poverty, vulnerability and food insecurity remain high. Shaping research priorities and
developing and disseminating innovative technologies are central to dealing with climate
change, reducing negative environmental impacts and improving the sustainability of tea
production.
Developing new models for predicting the impact of climate
change on tea cultivation
There are numerous models for predicting change in the climate itself, such as the extent
of average temperature changes and shifts in precipitation patterns. Many models also
predict the effects of climate change on crop production. However, few focus specifically
on tea cultivation. It is therefore necessary to develop specific models for predicting future
climate change in tea-growing regions and their impact on tea cultivation. Parameters
in the simulation models should include not only mean temperature, precipitation and
CO2 concentrations, but also the climate variability and extremes. The impact of climate

© Burleigh Dodds Science Publishing Limited, 2018. All rights reserved.
Tea cultivation under changing climatic conditions 13
change on tea production should focus on tea quality and the suitability of tea-growing
areas, as well as on yield. Quantitative analysis should be included in the prediction
models. Early warning and monitoring systems should be established according to the
results of predictive models.
Reducing emissions of greenhouse gases
The continued emission of greenhouse gases will cause further warming and changes in
all components of the climate system. Substantial and sustained reductions of greenhouse
gas emissions, such as the use of clean development mechanisms in tea growing, could
limit climate change while not compromising production. N2O is a key greenhouse gas
produced in tea soils. Tea, as a leaf harvest crop, is fed with large amounts of fertiliser,
especially those which are nitrogen-based. The annual nitrogen application rates in typical
Chinese tea fields ranged from 0 to 2600 kg/ha with an average of 553 kg/ha (Han and
Li, 2002). When 300, 600 and 900 kg N/ha are applied, N2O-N emissions accounted
for 1.43%, 1.96% and 3.44% of the nitrogen applied, respectively (Han et al., 2013b).
Reducing nitrogen application, by using slow-release nitrogen fertilisers and balanced
fertilisation, can significantly increase the efficiency of nitrogen use (Han et al., 2008).
Additional technologies and practices should be developed to increase nitrogen use
efficiency and reduce N2O emissions. The reduction of CO2 emissions could also improve
soil quality through increasing soil organic carbon.
Enhancing carbon sequestration
Increasing soil organic matter not only enhances carbon sequestration, but also improves
water retention capacity, soil structure and the biodiversity which increases yield and
improves soil resilience to flooding, erosion, drought and heavy rainfall. Increasing soil
organic matter also improves nitrogen use efficiency. In the case of China, the average
organic carbon in the top 0–40 cm of topsoil is only 1.08% (Han et al., 2002). An increase
in topsoil organic carbon of 0.1% could increase sequestration by 5.2 ton/ha, or 13.78
million tons, equivalent to 50.52 million tons of CO2 in the Chinese tea sector. There
is great potential in carbon sequestration and new technologies should be developed
to increase soil organic matter along with organic farming, GAP, no or low tillage and
mulching.
Developing new resistant cultivars
There is an urgent need to develop new tea cultivars to deal with climate change. These
will need high tolerance to heat, cold and drought stress, high resistance to pests and
diseases, high nitrogen nutrient use efficiency and high net photosynthesis, especially
in response to higher CO2 concentrations. For example, tea cultivars with characteristics
of deep-growing roots and high metabolite content (e.g. amino acids and sugars) have
proved highly resistant to drought (Thiep et al., 2015; Nyarukowa et al., 2016).
Improving soil and water conservation capacity
Climate change has a negative effect on the basic elements of food production, such
as soil, water and biodiversity. Most tea fields are located on the rain-fed slopes of
mountainous areas in which tea yields depend not only on the amount of rainfall, but also

Tea cultivation under changing climatic conditions
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© Burleigh Dodds Science Publishing Limited, 2018. All rights reserved.
on its utilisation. With increasing temperatures and high evaporation and transpiration,
drought will probably be a normal phenomenon in the coming years. Therefore, to
develop soil and water conservation measures, increasing soil water holding capacity will
be very important in reducing the impact of drought and maintaining tea production.
Besides establishing contour terraces, mulching, planting cover crops and installing
contour-staggered trenches, ecosystem diversity and water conservation agents should
be considered for further research and development. Adopting small-scale irrigation in tea
fields will also increase resilience to drought.
Improving integrated tea production ecosystems
Tea is a perennial, mono-cultured crop and tea farm ecosystems are generally simple.
Creating more diverse tea agro-ecosystems could maximise adaptation to hot weather,
flooding or drought and increased CO2. Proper shade management and eco-agricultural
models, such as pig raising – biogas slurry – tea, and tea – green manure – animal husbandry
– biogas slurry – tea should be further studied and promoted. Conservation agriculture,
precision agriculture, organic agriculture and other sustainable farming systems should all
be integrated in adaptation to climate change.
6.3 Community involvement and technology extension
Smallholder tea farms account for 60% of tea production globally and are more vulnerable
to the impacts of climate change than larger farms. In addition to the development of
new technologies and techniques, awareness of climate change and its impact, public
education, information exchange, indigenous and community-based adaptation strategies
and the extension of new technology, crop insurance should be promoted to deal with
climate change and extremes.
Creating awareness of climate change and its impact
Public awareness of climate change and its impact on the tea industry is one of the key
strategies in implementing effective participatory climate adaptation on a large scale.
Public access to information on climate change and its effects, especially those specific to
the region of target audiences, should be made available in local communities.
Extending mitigation and adaptation measures
Climate change mitigation and adaptation measures should be extended immediately,
especially in the most vulnerable areas and in key tea-producing areas. Indigenous and
community-based measures should be encouraged. New and integrated adaptation
measures should be tested or evaluated locally before extension on a large scale.
Community and individual participations in national or regional adaptation planning
processes should be encouraged. Technical and financial support, scientific and managerial
personnel training and other capacity-building programmes should be strengthened in
local communities.
Common mitigation and adaptation measures comprise the planting of drought-
tolerant cultivars, increased application of organic fertilisers, adoption of irrigation and
water harvesting techniques, mulching, inter-cropping for higher diversity and balanced
ecosystems, better infrastructure and early warning and monitoring systems. Farmers

© Burleigh Dodds Science Publishing Limited, 2018. All rights reserved.
Tea cultivation under changing climatic conditions 15
located in areas which are likely to become unsuitable for tea cultivation in the future
need to identify alternative crops. The use of local or indigenous/traditional knowledge
is also an important aspect which needs to be revived and promoted with appropriate
scientifically based evidence.
Developing crop insurance to minimise the risks of
meteorological disasters
Tea producers, especially small holders and low-income farmers, should be encouraged
to purchase meteorological disaster insurance to reduce the risks of climate impacts.
Insurance for late spring cold spells is currently sold by the leading insurance companies in
China and is supported by the government of Zhejiang Province. The increasing frequency
of extreme weather events, such as drought, and related change in ecosystems such as
pest outbreaks will seriously affect tea production. More insurance schemes should be
developed and promoted.
7 Conclusion
The world has witnessed a significant upsurge in climate change and it will continue even
in greater pace in the coming decades. Climate change does not only mean the rising
temperature and CO2 elevation; the extreme weather events, such as drought, heavy
precipitation and frost, will also be more and more frequent, which has a huge negative
impact on tea production. Therefore, it is necessary to develop management strategies
to cope with climate change in order to reduce the risks and promote sustainable
development of the tea industry.
With the increase of temperature, the currently well-known tea-growing regions
might not be suitable for cultivation and would shift to higher latitudes and higher
altitude ecosystems, and the tea-growing period can be lengthened in subtropical
areas. Tea production would be benefited by temperature increase and CO2 elevation,
but significantly affected by drought, heavy rains, frosts and proliferation of pests
and diseases, and soil degradation. Tea quality would be deteriorated if the ratio
of free amino acids to polyphenols is unbalanced. An appropriate plan for climate
change adaptation and mitigation should be developed and extended for sustainable
development of tea industry. The adaption and mitigation strategies should have three
levels: government policy, R&D for new technologies and techniques and community
involvement and technology extension, which should be integrated and implemented
immediately.
8 Where to look for further information
IPCC Fifth Assessment Report, http://www.ipcc.ch/publications_and_data/publications_
and_data_reports.shtml#1
Han W. Y., Li X. and Ahammed J.G. (Eds.) 2018. Stress physiology of tea in the face of
climate change, Springer Nature Singapore Pte Ltd, Singapore.

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© Burleigh Dodds Science Publishing Limited, 2018. All rights reserved.
9 Acknowledgements
This work was supported by the Science and Technology Innovation Project of the Chinese
Academy of Agricultural Sciences (CAAS-ASTIP-2015-TRICAAS-08) and the Basal Research
Fund of the Chinese Academy of Agricultural Sciences (1610212016025). The authors
appreciate the valuable suggestions and English revision of Dr. Eric R. Scott.
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