S. K. Guru
1.5 Adjustment
It is certain that in an event of any climate change, agriculture will adjust to meet these changes, which is likely with a spatial shift of crop potential. Areas under today’s climatic conditions suited for a crop or combination of crops may no longer be suit- able after a climatic shift, or otherwise, an area today not suit- able for growing particular crop(s), may be suitable tomorrow (Chakravarty and Mallick, 2003). Maize growing successfully in South England at present may shift northward with a rise in temperature, wheat will shift eastward in the United States (Decker et al., 1985), north and southward in India and maize northward in the United States (Newman, 1980). Similar north- ward shifts are projected for sunflower in the UK (Parry et al., 1989), citrus, olives and vines in southern Europe (Imeson et al., 1987), while a southward shift of land use is projected in the Southern Hemisphere (Salinger, 1988). This might also expand successful commercial production of mangoes, papa- yas, litchis, bananas, pineapples and other fruits from sub-trop- ical and tropical to temperate areas (Chakravarty and Mallick, 2003).
Changes in climate would influence agriculture by chang- ing the length of the growing season, crop yield, agricultural potential and shifting the geographical area (Hogg, 1992).
Many crops can adjust to possible climate change. However, the magnitude of the projected climate will shift northward as change will vary from location to location and the influence will be a function of the change in climate to the existing condi- tion (Chakravarty and Mallick, 2003). So at mid latitudes, agri- cultural potential would decrease toward poles due to smaller
table 1.4Climate change impacts on Indian crop production CropRegionTemperatureCO2 levelProduction impactReference RiceUttarakhandIncreasedDoubledPositiveAchanta (1993) IndiaHighIncreasedIncrease in production under the global circulation model (GCM) scenarioMohandass et al. (1995) KeralaUp to 5°C rise425 ppmIncrease in production due to fertilisation effect of CO2 up to 2°C and also enhances water-use efficiency but up to 5°C temperature, there is a continuous decline in rice yield
Saseendran et al. (2000) Central, South and North-West0.7°C and 1°C increase
—Central and South India production will increase but in the North-West, production will decrease significantly under irrigated condition due to decrease in monsoon rainfall. Reduction in crop duration all over due to temperature increase
Rathore et al. (2001) Northern, southern, western and eastern
1–4°C rise450 ppmEastern and western less affected, northern moderate and southern severely affected. With CO2 of 450 ppm and 1.9–2°C increase, production increased in all regions
Aggarwal and Mall (2002) IndiaAtmospheric brown clouds (ABC)
IncreaseAuffhammer et al. (2006) Rice, wheatNorthern coastal regions0.5–2°C riseDecrease in rice and wheat yields and would reduce wheat crop duration by 7 daysSinha and Swaminathan (1991) North-West India2–3°C riseIncreasedDoubling CO2 increases rice and wheat yield but at 3°C for wheat and 2°C for rice nullified the positive effects of increased CO2
Lal et al. (1998) continued
table 1.4(continued)Climate change impacts on indian crop production CropRegionTemperatureCO2 levelProduction impactReference Wheat, rice, maize, groundnut
Punjab1°C, 2°C and 3°C increaseIncreasedYield reduction in all the crops. Increased CO2 increases crop productionHundal and Kaur (1996) Wheat, winter maizeBiharIncreasedIncreasedYield increase in winter maize but decrease in wheatAbdul Haris et al. (2013) WheatIndia1°C increase—Yield reductionSaini and Nanda (1986) Northern India0–2°C rise425 ppmAt 1°C yield increased but reduced at 2°C with reduced evapotranspirationAggarwal and Sinha (1993) IndiaIncreased—Yield decreasedGangadhar Rao and Sinha (1994) North, Central India at high and lower latitude; tropical and sub-tropical 0–2°C rise425 ppmAt 1°C yield increased but reduced at 2°C temperature. Sub-tropical reduction by 1.5–5.8 % but in tropical decrease was 17–18 %. Slightly increased at high latitudes but significant decrease at lower latitude. 10–15 % yield reduction in Central India but non- significant in north
Aggarwal and Kalra (1994) SorghumHyderabad, Akola and SholapurThree scenarios of climate change
IncreasedYield reduction at Hyderabad and Akola but at Sholapur marginally increasedGangadhar Rao et al. (1995) India1–2°C rise50–700 ppm7–12% reduction in yield. 50 ppm CO2 increase, yield increased by 0.5% but was nullified with a rise of 0.08°C and 700 ppm by a rise of 0.9°C
Chatterjee (1998)
MaizeIndiaUp to 4°C rise350–700 ppmDecreased yield in both irrigated and rainfed conditions. With 350 ppm CO2 and up to 4°C yield decreased by 30% but at 700 ppm CO2 yield increased by 9% over present day condition
Sahoo (1999) BrassicaNorthVariedVariedProduction is likely to increase and extend its range at relatively drier regionsUprety et al. (1996) Chickpea, pigeon peaIndiaUp to 2°C rise350–700 ppmChickpea yield not increased with reduction in total crop duration but increase in CO2 increased yield while yield of pigeon pea decreased at 1°C increase
Mandal (1998) Soya beanCentral3°C rise with 10% decline in rainfall
Doubled50% yield increase in Central India but at 3°C increase no effect of doubling CO2 as yield reduced which was acute at reduction of daily rainfall decreasing yield by 32%
Lal et al. (1999)
thermal inputs, while the same increase of temperature will have a greater relative effect at higher latitudes than at lower latitudes due to greater temperature increases at higher latitudes (Parry et al., 1990). Considering the examples of the adjustment and yield increase of wheat in India, maize in Iowa, United States and northern Europe, rice in Philippines and Indonesia, soya bean in Brazil, sunflower in the Red Valley of the United States, oil palm in Malaysia and canola (rape) in Canada, the future adjustment of agricultural crop production can also be indexed by an already observed rate of change (Wittwer, 1990).
Global warming projection, especially during winter months at high latitudes (Williams and Oakes, 1978; Parry et al., 1988, 1989; Wittwer, 1990), will extend the efficient crop ecological zone indicating a significant northward shift of balance of agri- cultural resources (Parry et al., 1989).
The extent of this crop ecological zone may not make the introduction of new genetic material necessary as it would advance the thermal limit of cereal cropping in mid-latitude Northern Hemisphere regions by about 150–200 km and raise the altitudinal limit by about 150–200 m in the European Alps, making it similar to the Pyrenees located 300 km south of the Alps (Parry et al., 1989). A rise of temperature in cool temper- ate and cold regions will lengthen the potential growing sea- son and increase growth rates. This will shorten the required growing period (except where moisture is a limiting factor), as in Finland where yields of barley and oat will increase by 9–18% (Kethunen et al., 1988), in Iceland where the carrying capacity of grasslands for sheep will increase by two and half times (Bergthorsson et al., 1988) and critically low-yield steppe regions will have a twofold increase in yields (Sirotenko et al., 1997). In areas presently with low precipitation, the elevated CO2 concentration will be beneficial to the crop yields as in China during summer monsoon where an increase in 100 mm rainfall with 1°C temperature rise will increase yields of rice, maize and wheat by 10% (Zhang, 1989) and similarly in Japan (Yoshino et al., 1988). The projected climate change due to an increase in CO2 concentration will favour a change from the existing, often quick maturing cultivars to be grown for a lon- ger and more intense growing season and late maturing variet- ies will be more suitable for such conditions. For instance, late growing rice cultivars presently in Central Japan will have a yield increase of 26% and quick maturing varieties now grow- ing in northern Japan will have increase of only 4% (Yoshino et al., 1988). Similarly, a switch to winter-sown cereals (wheat, barley and oats), as in the case of wheat in Saskatchewan and
Central Russia, will give higher yields than spring cereals because of longer growing seasons and reduced damage by high evapotranspiration rates (Pitovranov et al., 1988).
The establishment of new zones of agricultural potential is likely to bring about changes in crop location and crop varieties.
These changes will however be influenced by the regional pat- tern of rainfall or variation in soils and competitiveness of different crops (Parry et al., 1990). For instance, cereal crop production in Europe will not be influenced as significantly as elsewhere. Crop production will suffer most severely in the inherently vulnerable regions of Africa, South America, Middle East, Asia Pacific, South-East and Central Asia where changes in temperature and precipitation will further stress the already limited productive capacity of these regions. Cold and mar- ginal regions of both the Northern and Southern Hemisphere (Canada, Alaska, Iceland, Scandinavia, Russia, New Zealand, Tasmania and others) will benefit from higher temperatures and its associated optimum conditions, such as longer growing seasons, higher growing degree units and more frost-free peri- ods with higher yields (Smit et al., 1989). If the climate change will occur as predicted, the agricultural production is likely to increase in North America, northern Europe, Commonwealth of Independent States, China and South America (Rosenzweig, 1985; Wilks, 1988; Wittwer, 1990). The crop yield of the Soviets and other European countries will boost by 50% while China and India will benefit with enhanced production of soya beans, winter wheat, rice, corn and cotton with northern migration.
But there are also areas where productivity of some crops will not change after an increase in CO2 concentration; for example, wheat production in major areas of the United States would remain the same (Hansen et al., 1981).
The projected climate change will bring about a large num- ber of changes in crop management that will modify the climate change on agriculture. Some regions and crops are critically more vulnerable than others (Chakravarty and Mallick, 2003).
Resources for crop production are usually most critical in agri- culturally developing countries than in developed countries (Oram, 1985). The climate change scenarios considered by vari- ous models would relax the current constraints imposed by a short and cool frost-free season, but without adjustive measures drier conditions and accelerated crop development rates were estimated to offset potential gains stemming from elevated CO2
concentrations (Brklacich et al., 1996). Under such conditions, higher crop yield would require greater amounts of fertiliser and water (Wittwer, 1990). The yields of major crops in dry and arid
tropical and sub-tropical areas will decrease as irrigation water will become limiting because of additional stress on crops already affected by higher temperatures (Beran and Arnell, 1989). A sub- stantial increase in cost and management of irrigation water is likely to occur in these areas. A northern migration of agriculture would increase irrigation and fertiliser in sandy soils, which may create worse groundwater problems (Wittwer and Robb, 1964).
Such a situation is most likely in Punjab and surrounding areas (Chakravarty and Mallick, 2003). In areas where the amount or intensity of rainfall will increase, management would be oriented in a way to prevent soil erosion. Moreover, increases in fertiliser use may be required in such areas. Thus, the agricultural produc- tivity impacts in most developing countries of Central and South America, Africa, South-East Asia and the Pacific Islands will be minimal through a combination of agricultural zones and adjust- ments in agricultural technology and management (Parry et al., 1990; Wittwer, 1990).