1、1860 单词， 2628 汉字 出处： Wijeratne M A. Vulnerability of Sri Lanka tea production to global climate changeJ. Water Air & Soil Pollution, 1996, 92(1-2):87-94. 原文 VULNERABILITY OF SRI LANKA TEA PRODUCTION TO GLOBAL CLIMATE CHANGE M.A. WIJERATNE Introduction Although industrial exports such as textiles and
2、 garments bring in a higher percentage of foreign exchange, agriculture is the highest net foreign exchange earner in Sri Lanka. Of the agricultural exports, tea alone contributes about 15-25% of the total exchange earnings and, hence, plays a key role in the Sri Lankan economy. About 30% of the emp
3、loyees of the public sector government and semigovernment are manual workers on estates, and the majority of these are employed on tea plantations. Moreover, about 239,000 tea small holdings also generate a large proportion of employment opportunities in the country. Accordingly, more than 700,000 w
4、orkers and their families are dependent on the tea industry. These figures show the importance of the tea industry to the social and economic stability of Sri Lanka In spite of the expansion of the small holdings sector, in Sri Lanka, the total area of tea plantations has decreased since the 1930s,
5、i.e., from about 0.44 to 0.23 x 10 s ha. The decline in the estate sector tea lands began early in the 1960s, because of low productivity brought about by soil and bush debilitation. Many of the midcountry 600-1,200 m elevation tea plantations have now become marginal, warranting crop diversificatio
6、n. Adversities of weather and poor management practices have been blamed for this situation； changes in the microclimate in tea plantations after shade removal during the early 1960s have also affected the productivity of the tea bushes Fuch, 1989. Some adverse effects of the nationalization of the
7、plantations in the 1970s, such as the neglect of agricultural practices, contributed to the decline in the estate sector production Fuch, 1989. Being a rainfed plantation crop in Sri Lanka, tea depends greatly on weather for optimal growth. Therefore, changes in weather conditions would undoubtedly
8、affect tea production. The relationship between tea yield and weather has been discussed by many researchers e.g., Devanathan, 1975； Kandiah and Thevadasan, 1980； Carr and Stephens, 1992. The findings of this study differ from those of the Sri Lanka country report ADB, 1994. This could be due to the
9、 different models used to predict tea yield. It is generally accepted that an increase in temperature increases tea yield, and this relationship has been used in many models. But recent findings show that at higher temperature regimes greater than 25-26 C, the increase in temperatures reduces tea yi
10、eld . Droughts inflict irreparable losses to the tea industry and hence to the economy of Sri Lanka. The consequences of the droughts in 1983 and 1992 are good examples Central Bank, 1983； 1992. The decline in production due to drought in early 1983 was about 4% over the previous year, and the droug
11、ht in 1992 reduced tea production by about 26% compared to that of 1991. It also increased the costs of production by 19%, depriving the country of about 3 billion rupees US$70 million of foreign exchange. Total production in 1991 and 1992 was 240.7 and 178.9 10 kg, respectively, and the latter was
12、the lowest production recorded since the end of the 1950s Figure 1. These figures show the magnitude of the loss that could be incurred by adversities of weather Heavy rainfall also causes considerable damage to tea plantations through soil erosion, poor growth due to lack of sun, and increases in d
13、isease incidence. Poorly covered old seedling tea fields, pruned tea fields, and young tea fields during the first two years are more vulnerable to soil erosion due to inadequate ground cover. It has been estimated that more than 30 cm of top soil has already been lost from Sri Lankas tea plantation
14、s, especially in the uplands Krishnaraj ah, 1985. Landslides also adversely affect plantations and endanger the lives of workers on the hilly slopes. Climate Change and Methods According to climate change scenarios, the increases in global atmospheric CO 2 concentrations and temperatures by 2100 cou
15、ld be in the range of 600-700 ppm and 1.0-3.5 C, respectively, compared to 1990, depending on different scenarios of variations in greenhouse gas emissions CO2, CH4, N20 and oceanic changes Houghton et al., 1996The consequences of climate change will differ from one country to another. In the recent
16、ly published Sri Lanka country report ADB, 1994, it was shown that Sri Lanka will experience frequent droughts, warmer spells, and extreme rainfall events as a result of the climate change. Scenarios &temperature changes for Sri Lanka show an increase in temperature of 0.4-3.0C by 2070 ADB, 1994. Mo
17、reover, climate change scenarios presented for Sri Lanka have shown that the frequency and severity of such extreme weather conditions may increase, and thus affect the agriculture sector. It is also indicated that there will be a 10% increase in the length of dry and wet seasons per year in the mai
18、n tea plantation area. Although an increase in rainfall is predicted, any significantly favorable impact on tea plantation agriculture is unlikely because of increased evaporation losses brought about by high temperatures and the possibility of the distribution of rainfall being erratic or uneven AD
19、B, 1994. In many other countries, vulnerability assessments on different economically and socially important areas are being conducted to inform policy makers about suitable adaptation measures that could be implemented. Hence, it has become a current need to address the possible impacts of global c
20、limate change on the tea industry in Sri Lanka . In this study, the effects of environmental factors on growth and yield of tea were studied using data on annual variation of climatic factors and yield parameters of tea. The relationship between the climatic factors and tea yield was analyzed using
21、linear regression analysis. Results and Discussion As described previously, since there is no irrigation, tea yield is greatly influenced by weather Tea grows well under air temperatures in the range of 18-25 C Carl 1972； Watson, 1986. A well-distributed rainfall of about 1,300-1,400 mm per year is
22、generally considered adequate for the growth of tea in Sri Lanka. It is also reported that an annual rainfall of about 2,500-3,000 mm is optimum for tea cultivation Fuch, 1989； Watson, 1986. There is a wide variation in temperature and rainfall in the different tea growing regions in Sri Lanka . Alt
23、hough the relationship between weather and tea yield has shown that increases in rainfall and temperature increase tea yield Devanathan, 1975； Squire, 1990, recent observations have shown that at higher temperature regimes 25-26 C, the yield components of tea shoot population density, shoot weight,
24、and shoot extension rate tend to decrease with increasing temperatures: SW=0.647 (4-0.059)- 0.017 (4-0.002 T ) R2 =40%, p 0.001 , and SER=225 38- 6.62( 1.37) T R2=29%, p 0.001 , where SW, SER, and T are the shoot dry weight g/shoot, shoot extension rate mm/week, and temperature C, respectively. Low
25、R 2 values were obtained because this experiment was conducted under field conditions where none of the environmental factors were controlledFigure 2 shows the relationship between tea shoot population density and temperature for TRI 2025 and TRI 2023, two common tea clones cultivars in Sri Lanka. E
26、xperiments under controlled environments have shown that shoot extension rate increases with increasing temperatures up to 22C, and further increases in temperature up to 34C result in a decline in the extension rate Figure 3； the dashed lines below 15 C in the figure are extrapolations of the linea
27、r relationship to obtain the base temperature above which tea grows . The adverse effects of climate change are expected to be greater in the low country tea growing regions 600 m above mean sea level where the mean air temperatures are usually higher than 25C and drought damages are greater. Howeve
28、r, this is the region where the majority of tea production enters the market Figure 4. Further, most of the small holdings are concentrated in the low country districts The effects of drought on tea plantations are well known Wijeratne and Ekanayake, 1990； Navaratne, 1992； Yatawatte, 1992. Increases
29、 in temperature, soil moisture deficit, and vapor pressure deficit create a plant water deficit, which leads to growth retardation. Experimental results in the low country have shown that clonal tea yields could be adversely affected at temperatures 26C, soil moisture deficits 30-50 mm, and saturati
30、on vapor pressure deficits 1.2 kPaWijeratne, 1994. Given these results, it could be assumed that the predicted climate change for Sri Lanka, i.e., higher temperatures and drier weather ADB, 1994, will be unfavorable for tea production. Extreme rainfall events within a short period of time also cause considerable damage through erosion. Loss of fertility, reduction in water holding capacity because of an increase in graveliness, exposure of hard pans, exposure of root systems, and
