Presentation on theme: "Status of climate change/variability studies and potential impacts of climate change/variability on national and regional agriculture, rangelands, forestry."— Presentation transcript:
Status of climate change/variability studies and potential impacts of climate change/variability on national and regional agriculture, rangelands, forestry and fisheries in RA-II region by H. P. Das Division of Agricultural Meteorology India Meteorological Department
Major risks due to climate change The following are the major risks in Asia apprehended from climate change: The frequency of forest fires is expected to increase in boreal Asia. Increased precipitation intensity, particularly during the summer monsoon, could increase flood prone areas in temperate and tropical Asia. There is a potential for drier conditions in arid and semi-arid Asia during summer, which could lead to more severe droughts. Crop production and aquaculture would be threatened by a combination of thermal and water stresses, sea level rise, increased flooding, and strong winds associated with intense tropical cyclones.
Present trend and variabilities in key climatic variables Surface air temperature Boreal Asia (Humid and cool-Continental type) Increase of C/100 years (more pronounced during ) Increase of C/100 years during the winter Decreasing trend in Central Siberia Arid and Semi-arid Asia (Warm temperate type) Increase of about C/100 years in the arid regions of China. Increasing tendency is also observed in Middle East, Kazakhstan and Pakistan The highest value of 20 0 C DTR is exprienced in this region Temperate Asia Increase of about C/50 years in Mangolia Increasing tendency during winter but decreasing tendency in summer in Northeast China Decrease of C in parts of South east China Warming trend in Japan during the past century Tropical Asia The warming trend in India, Pakistan, middle East, Vietnam ( C/30 years) Sri Lanka ( C/100 years) Increasing trend in southern and central India in all seasons and over all of India in the post-monsoon seasons. DTR shows an increasing trend in all the seasons over most of Peninsular India
Present trend and variabilities in key climatic variables Precipitation Boreal Asia where rainfall is highly variable on seasonal and interannual as well as spatial scales. Mean annual precipitation in Russia suggests a decreasing trend, particularly during , specially in warm years. However, a decreasing trend of about 4.1 mm/month/100 years in Boreal Asia. During the past years, however, precipitation has increased mostly during the summer-autumn period. As a result of this increase in precipitation, water storage in a 1 mm soil layer has grown by mm. The large upward trend in soil moisture (of more than 1cm/10 years) have created favourable condition for infiltration into ground water. The levels of major acquifers have risen by cm. Arid and semi-arid region of Asia where rainfall is considerably low but temporal variability is quite high. Mean annual precipitation shows an increasing trend during the past 50 years in some countries in the northern part of this region. However, a decreasing trend in annual precipitation has been observed in Kazakhstan during the period , but increasing trends observed during spring, summer and autumn. In Pakistan, seven out of 10 states have shown increasing tendency during summer season.
Precipitation (Contd..) Temperate Asia where the East Asian monsoon greatly influences temporal and spatial variation in rainfall Summer rainfall seems to have declined over the period in Gobi, the number of days of heavy rainfall events has dropped significantly. In China, annual precipitation has been decreasing since This decrease has become serious since the 1980s. The summer monsoon is reported to be stronger in northern China during globally warmer years, but drier condition have prevailed over most of the monsoonal area during colder years. Tropical Asia where hills and mountain ranges cause striking spatial variation in rainfall The annual mean rainfall in Sri Lanka is practically trendless, positive trend in February and negative trends in June have been reported. A long-term decreasing trend in rainfall in Thailand is reported. In Bangladesh, decadal departures were below long-term averages until 1960, but afterwards they were above normal. In India, time series of summer monsoon rainfall have no discernible trends but decadal departures are found above and below the long-term averages alternatively for 3 consecutive decades. Recent decades have exhibited an increase in extreme rainfall events over northwest India during the summer monsoon. The number of rainy days along the eastern coast has declined in the past decade.
Status of extreme and severe weather systems There is some evidence of increase in the intensity or frequency of some of extreme weather events like heat waves, extratropical and tropical cyclones, prolonged dry spells, intense rainfall, tornadoes, snow avalanches, thunder storms, dust storms etc on regional scales in widely separated areas of Asia throughout the 20th century. Boreal Asia Increases in climate extremes in the western Siberia-Baikal region and eastern parts of boreal Asia have been reported in recent decades. Some mountains in Asia have permanent glaciers that have vacated large areas during the past few decades, resulting in increases in glacial runoff. As a consequence, an increased frequency of events such as mudflows and avalanches affecting human settlements has occurred. As mountain glaciers continue to disappear, the volume of summer runoff eventually will be reduced as a result of loss of ice resources. Consequences for downstream agriculture, which relies on this water for irrigation, will be unfavorable in some places. For example, low and mid-lying parts of central Asia are likely to change gradually into more arid, interior deserts. Temperate Asia In China, droughts in 1972, 1978, and 1997 have been recorded as the most serious and extensive. A large number of severe floods also have occurred in China, predominately over the middle and lower basins of the Yangtze (Changjiang), Huanghe, Huaihe and Haihe rivers. In Japan, drought disasters are significantly more frequent during years following ENSO warm events than in normal years.
Status of extreme and severe weather systems (Contd..) Tropical Asia No identifiable variability in the number, frequency, or intensity of tropical cyclones or depressions has been observed in the northern Indian Ocean cyclone region (Bay of Bengal and Arabian Sea) over the past 100 years, although there was some evidence of decadal scale variations with a rising trend during and a declining trend since that time. No conclusive increasing or decreasing trends in time series data of flooded areas has been noticed in various river basins of India and Bangladesh. In India, Laos, the Philippines, and Vietnam drought disasters are more frequent during years following ENSO events. At least half of the severe failures of the Indian summer monsoon since 1871 have occurred during El Niño years. It is found that the and periods witnessed frequent droughts while few droughts occurred during and This suggests some kind of low frequency oscillation of the monsoon system on the decadal scale. There are also reports of an increase in thunderstorms over the land regions of tropical Asia. Arid and Semi-arid Asia Over arid and semi-arid regions of India there have been periods in the last decades of the nineteenth century and first two decades of twentieth century when drought frequencies have been markedly higher than in recent years, although individual recent droughts may have been intense ones in some regions. The frequency and severity of wild fires in grassland and rangelands in arid and semi-arid Asia have increased in recent decades. Coupled with the conversion of grazing lands to farming, the arid regions of India is undergoing an aggravation of desertification through erosion of lands and aeolian shifting of soil particles. In some locations, there has been a rise in water table with simultaneous increase of salinity and deterioration of soil regime. The variation of the aridity index line, computed by Penman method, over arid regions of India reveals a possible spread of arid conditions in southeast direction.
2020s Temperature Change 0 C) 2050s2080s RegionsAnnualWinterSummerAnnualWinterSummerAnnualWinterSummer Asia1.58 (1.36) 1.71 (1.52) 1.45 (1.23) 3.14 (2.49) 3.43 (2.77) 2.87 (2.23) 4.61 (3.78) 5.07 (4.05) 4.23 (3.49) Boreal2.17 (1.88) 2.66 (2.21) 1.71 (1.47) 4.32 (3.52) 5.52 (4.46) 3.29 (2.83) 6.24 (5.30) 8.04 (6.83) 4.82 (4.24) Arid/Semi-arid Central Asia 1.61 (1.47) 1.56 (1.55) 1.77 (1.49) 3.18 (2.69) 2.81 (2.61) 3.55 (2.59) 4.83 (4.15) 4.41 (3.78) 5.34 (4.36) Tibet1.77 (1.56) 1.90 (1.83) 1.62 (1.40) 3.38 (2.62) 3.55 (2.94) 3.19 (2.27) 5.04 (4.06) 5.39 (4.32) 4.69 (3.73) Temperate1.49 (1.19) 1.74 (1.50) 1.23 (0.99) 2.86 (2.10) 3.26 (2.40) 2.48 (1.72) 4.34 (3.31) 5.11 (3.83) 3.67 (2.77) Tropical South Asia 1.36 (1.06) 1.62 (1.19) 1.13 (0.97) 2.69 (1.92) 3.25 (2.08) 2.19 (1.81) 3.84 (2.98) 4.52 (3.25) 3.20 (2.67) SE Asia1.05 (0.96) 1.12 (0.94) 1.01 (0.96) 2.15 (1.72) 2.28 (1.73) 2.01 (1.61) 3.03 (2.49) 3.23 (2.51) 2.82 (2.34) Table 1 Possible changes in area-averaged surface air temperature over Asia and its sub-regions as a result of future increases in greenhouse gases. Numbers in parenthesis are area-averaged changes when direct effects of sulphate aerosols are included.
Extreme events – Future scenario Recent observations suggest that there is no appreciable long term variation in the total number of tropical cyclones observed in the north Indian, southwest Indian, and southwest Pacific Oceans east of E. The frequency of typhoons and the total number of tropical storms and typhoons has been more variable since about Some studies suggest an increase in tropical storm intensities with carbon dioxide (CO 2 ) induced warming. Some of the most pronounced year-to-year variability in climate features in many parts of Asia has been linked to ENSO. Future seasonal precipitation extremes associated with a given ENSO event are likely to be more intense in the tropical Indian Ocean region; anomalously wet areas could become wetter, and anomalously dry areas could become drier during ENSO events. The intensity of extreme rainfall events is projected to be higher in a warmer atmosphere, suggesting a decrease in return period for extreme precipitation events and the possibility of more frequent flash floods in parts of India Nepal, and Bangladesh. No significant change is found in the number and intensity of monsoon depressions (which are largely responsible for the observed interannual variability of rainfall in the central plains of India) in the Bay of Bengal in a warmer climate.
Impact of climate variability and change on agriculture Boreal Asia where climate change could have serious effects on climate dependant sectors such as agriculture, forestry, and water resources Climate change and human activities, for example, may influence the levels of the Caspian and Aral Seas, with implications for the vulnerability of natural and social systems. The increase in surface temperature will have favorable effects on agriculture in the northernmost regions of Asia, and a general northward shift of crop zones is expected. However, as much as a 30% decrease in cereal production from the main agriculture regions of boreal Asia by 2050 has been projected. A decrease in agriculture productivity of about 20% also is suggested in southwestern Siberia. Forest ecosystems in boreal Asia could suffer from floods and increased volume of runoff, as well as melting of permafrost regions. Model based assessments suggest that significant northward shifts (up to 400 km) in natural forest zones are likely in the next 50 years. There also is growing anxiety that significant increases in ultraviolet radiation, as observed in recent years, could have serious implications for ecosystems along the Arctic shore of Siberia.
Impact of climate variability and change on agriculture (Contd…) Arid and semi-arid Asia where the climate limits the portion of land that presently is available for agriculture and livestock production. Croplands in many of the countries in the region are irrigated because rainfall is low and highly variable. The agriculture sector here is potentially highly vulnerable to climate change because of degradation of the limited arable land. Almost two thirds of domestic livestock are supported on rangelands, although in some countries a significant share of animal fodder also comes from crop residues. The combination of elevated temperature and decreased precipitation in arid and semi-arid rangelands could cause a manifold increase in potential evapotranspiration, leading to severe water stress conditions. Many desert organisms are near their limits of temperature tolerance. Because of the current marginality of soil water and nutrient reserves, some ecosystems in semi-arid regions may be among the first to show the effects of climate change. Climate change has the potential to exacerbate the loss of biodiversity in this region.
Impact of climate variability and change on agriculture (Contd…) Temperate Asia where the major impacts of global warming will be large northward shifts of subtropical crop areas. Large increases in surface runoff leading to soil erosion and degradation, frequent waterlogging in the south, and spring droughts in the north ultimately will affect agriculture productivity The volume of runoff from glaciers in central Asia may increase three fold by Permafrost in northeast China is expected to disappear if temperatures increase by 2 0 C or more. The northern part of China would be most vulnerable to hydrological impacts of climate change; future population growth and economic development here may exacerbate seriously the existing water shortage. Deltaic coasts in China would face severe problems from sea level rise. Sea-level rise also will expand the flood-prone area and exacerbate beach erosion in Japan.
Impact of climate variability and change on agriculture (Contd…) Tropical Asia where Agricultural productivity is sensitive not only to temperature increases but also to changes in the nature and characteristics of monsoon. In Bangladesh, the impact of climate change on high yield rice varieties was studied and found that the detrimental effect of temperature rise more than offset the positive effect of increased CO 2 level on rice. In India it was found that higher temperatures and reduced radiation associated with increased cloudiness caused spikelet sterility and reduced yields to such an extent that any increase in dry matter production as a result of CO 2 fertilization proved to be no advantage in grain productivity. Rice yields in east Java of Indonesia could decline by 1% annually as a result of increases in temperature. In tropical Asia, although wheat crops are likely to be sensitive to an increase in maximum temperature, rice crop would be vulnerable to an increase in minimum temperature. The adverse impacts of likely water shortage on wheat productivity in India could be minimized to a certain extent under elevated CO 2 levels; these impacts, however, would be largely maintained for rice crops, resulting in a net decline in rice yields.
Geographic Scope Yield Impact (%) Bangladesh -6 to +8 Bangladesh +10 Bangladesh -9 to +14 Thailand -17 to +6 Thailand sites -5 to +8 Thailand -12 to +9 Philippines -21 to +12 Philippines decrease Philippines -14 to +14 Indonesia -3 Indonesia approx. –4 Indonesia +6 to +23 Malaysia -22 to -12 Malaysia +2 to +27 Malaysia -14 to +22 Table 4 Yield impact of selected climate change studies for rice in Tropical Asia.
Cultivar (Station)RainfedIrrigated S-IIS-IIIS-IIS-III WH542(Hisar) HD2329(Ludhiana) HD2285(Delhi) Sonalika(Pantnagar) Raj3765(Jaipur) Table 5 Increase in yield (%) of different cultivars under modified climate of northwest India S-I :current climates S-II: T max C, T min C, 2 x CO 2 S-III: T max C, T min C, 2 x CO 2
RegionChanges of net revenue E4-ggCG-ggCG-gsH2-gsH2-gx (3.1 0 C, 10.4%)(4.7 0 C, 4.7%)(3.2 0 C, -6.2%)(1.3 0 C, 0.2%)(2.5 0 C, 10.4%) North (18.16)( )( )(39.37)(37.33) Northeast (-8.61)(-30.50)(-25.9)(-2.41)(-7.63) East (19.25)(-33.01)(-37.71)(52.71)(36.41) Central (13.89)(-38.36)(-54.27)(18.05)(21.97) South (15.76)(5.31)(11.05)(17.53)(20.20) Southwest (1.81)(-48.54)(-58.58)(2.73)(-4.13) Northwest (-4.27)( )( )(10.68)(12.51) Plateau (6.97)(-17.36)(-10.77)(4.29)(13.49) Total (11.95)(-68.09)(-68.88)(28.31)(23.62) Table 6 Possible impacts due to different climate scenarios in 2050s (billion Yuan)
Impact on boreal forests Climate change may affect the biodiversity in boreal forests of Asia through a myriad of processes and effects like local mortality of boreal species and replacement by northern hardwoods or prairies, migration of boreal species northward and coastward, increased probability of fire; increased or decreased soil nutrients availability, increased emissions of green house gases particularly methane from wetlands etc. Major alterations in vegetation could be expected, specially in the mountains of the northern boreals subzones and the subarctic forest – tundra ecotone in northeast Siberia. In the middle and southern boreals subzones, vegetation changes may be more limited because of more resistant species interaction in the forest communities of the continental area and the isolated islands of the Kuril, Shantar and Kommander groups. Impact of climate variability and change on forestry
(Contd..) Impact on temperate forests Studies on projected impacts of climate change suggest that northeast China may be deprived of the conifer forests and its habitat and broad leaved forests in east China may shift northward by approximately 3 0 of latitude. These results are based on a 2 0 C increase in annual mean temperature and a 20% increase in annual precipitation. Although the area of potential distribution of temperate forests in Temperate Asia is to a large extent, cleared and used for intensive agriculture, global warming can be considered to trigger structural changes in remaining temperate forests. The nature and magnitude of these changes depend on associated changes in water availability, as well as in water use efficiency. Shifts in temperature and precipitation in temperate rangelands may result in altered growing seasons and boundary shifts among grasslands, forests and shrublands.
Impact on tropical forests Results of research from Thailand suggest that climate change would have a profound effect on the future distribution, productivity, and health of Thailand’s forests. The area of subtropical forest could decline from the current 50 % to either 20 % or 12 % of Thailand’s total forest cover (depending on the model used), whereas the area of tropical forests could increase from 45 % to 80 % of total forest cover. A decrease in tropical rainforest of 2-11 % and an increase in tropical dry forest of 7-8 % in Sri Lanka. A projected depletion of soil moisture would likely cause teak productivity to decline from 5.40 m3/ha to 5.07 m3/ha in India. The productivity of moist deciduous forests also could decline from 1.8 m3/ha to 1.5 m3/ha. (Contd..)
Impact on Arid and Semi-Arid rangeland With an increase in temperature of C combined with reduced precipitation as projected for the future in the semi-arid and arid regions of Asia, grassland productivity is expected to decrease by as much as %. Rangelands in Nepal also have been subjected to degradation in recent years. Climate change is likely to represent an additional stress to rapid social change in many of Asia’s rangelands. Shifts in temporal biomass patterns due to changed climate have potentially significant implications for grazing management. Forest fires alter the structure of vegetation and affect nutrient cycling. By making nitrogen and other nutrients more available to soil microorganisms, fire may result in enhanced emissions of nitrous oxide (N 2 O) from soil.
Climate change impacts on fish species generally will be positive through faster growth, low winter mortality rates, reduced ice cover, and reduced energy costs as a result of expanded regions of warmer water. Cultivation of warm water species also may expand. Warming will require greater attention to possible oxygen depletion, fish diseases, and introduction of unwanted species. For marine fisheries, slight changes in environmental variables such as temperature, salinity, wind speed and direction, ocean currents, strength of upwelling, and predators – can sharply alter the abundance of fish population. Rises in sea level also may cause saline water fronts to penetrate further inland, which could increase the habitat of brackish – water fisheries. Coastal inundation also could damage the aquaculture industry. Fisheries at higher elevations may be particularly affected by lower oxygen availability resulting from increases in temperature. In the plains, the timing and amount of precipitation may affect the migration of fish species from the river to the flood plains for spawning, dispersal and growth. If the magnitude and extent of floods increase, more flood control projects would further deplete flood plain fisheries. Effect on Fisheries
Marine productivity is greatly affected by temperature changes that control plankton shift, such as seasonal shifting of sardine in the sea of Japan and induced during the cyclic occurrence of the ENSO in low latitudes. The impact of global warming on fisheries will depend on the complicated food chain, which would be disturbed by sea level rise, changes in ocean currents, and alteration of mixing layer thickness. The rise in the SST will shift the southern limit of salmon species further to the north. It is also suggested that the Sea of Japan bottom water will become anoxic within a few hundred years; a decreased oxygen supply will lead to major losses in biological productivity in deep waters. Increased frequency of El-Nino events, which are likely in the warmer atmosphere, could lead to measurable declines in plankton biomass and fish larvae abundance in coastal waters of south and southeast Asia. Such declines in lower levels of the food chain will have negative impacts on fisheries in Asia. Effect on Fisheries (Contd..)