Impact of climate change on agriculture and strategies f¬or its Reduction

Introduction

Climate change is considered as one of the major environmental problems of the 21 st century and today's major scientific and political issue. Climate is changing naturally at its own pace, since the beginning of the evolution of earth, 4-5 billion years ago, but presently, it has gained momentum due to inadvertent anthropogenic disturbances. These changes may culminate in adverse impact on human health and the biosphere on which we depend. The multi-faceted interactions among the humans, microbes and the rest of the biosphere have started reflecting an increase in the concentration of greenhouse gases (GHGs). Some external influences, such as changes in solar radiation and volcanism, occur naturally and contribute to the total natural variability of the climate system. Other external changes, such as change in composition of the atmosphere that began with the industrial revolution, are the result of human activities (IPCC, 2007) [7] . Research on the impact of climate change and vulnerability on agriculture is a high priority in India as the impact, if it follows the predictions, is expected to be widespread and severe. Developing the ability to confidently estimate the impacts of climate change on agriculture is critically important. If ever achieved, it could provide the global information needed to help farmers develop their own long-range response to climate change. Fortunately, we are very near to having such a capability, and it may take 5-7 years to substantially improve the resolution and accuracy of the climate model and evaluate the implications for agriculture.

Climate change: Current trends: According to IPCC (2007) [7] , global temperature has increased 0.9 0 C (1.62 F) since the 19 th century. Oceans are warming at the rate of 0.4 0 F, glaciers are retreating at the rate of 3.5 to 4% per decade in the artic. Moreover, ice sheets have been shrinking with Greenland losing 286 billion tons of ice per year between 1993 and 2016 and Antarctica losing 127 billion tons of ice. Extreme climatic events have resulted in over 725,000 victims, economic costs of US$700 billion and insured costs of US$125 billion (Munich Re, 2002) [14] . Sea level has been rising at the rate of 3 mm per year from 1993-2003 which may lead to various countries to disappear, especially the Island nations such as: Total annual anthropogenic greenhouse gas (GHG) emissions (gigatonne of CO2-equivalent per year, GtCO2-eq/yr) for the period 1970 to 2010. Source: IPCC, 2007 [7] Indian scenario Agriculture sector in India contributes to greenhouse to greenhouse affect primarily through the emission of GHGs such as CH 4 , N 2 O and CO 2 . Of the several sectors of agriculture, enteric fermentation contributes 211,429 Gg (51%), Paddy cultivation contributes 74,360 Gg (21%) and an emission from soil contributes 57,810 Gg (16%). Other sources are burning of crops residues and manure heaps (NATCOM, 2012) [15] .

Climate change: Future projections

Although there is considerable uncertainty about future, all climate models indicate a rising trend in temperature. By 2100 a rise of 1.8 to 4 o C is expected Source: IPCC, 2007 [7] Table 1: Climate change scenarios for South Asia (Source: IPCC, 2007) [7] Period Temperature ( 0 C)

Climate change effects: water

Global water use has increased by a factor of six over the past years (Wada et al., 2016) [21] . The global demand for water has been increasing at a rate of about 1% per year over the past decades as a function of population growth, economic development and changing consumption patterns, among other factors, and it will continue to grow significantly over the foreseeable future. Industrial and domestic demand for water will increase much faster than agricultural demand, although agriculture will remain the largest user overall. The vast majority of the growth in demand for water will occur in countries with developing or emerging economies. At the same time, the global water cycle is intensifying due to climate change, with wetter regions generally becoming wetter and drier regions becoming even drier. Other global changes (e.g., urbanisation, de-forestation, intensification of agriculture) add to these challenges (United Nations World Water Development Report, 2018) [19] .

Water scarcity a real global problem since around 700 million people in 43 countries suffer today from water scarcity. By 2025, 1.8 billion people will be living in countries or regions with absolute water scarcity.

So how does it affect agriculture?

Agriculture: 70% of global freshwater withdrawals reaching up to 90% in some fast-growing economies. Irrigation provides 40% of the world's production on less than 20% of the cultivated land and globally, irrigated crop yields are about 2.7 times those of rainfed farming.

Drought situation in India

About 60-70% of India is vulnerable. Productivity of most cereals would decrease due to increase in temperature and decrease in water availability (especially in Indo-Gangetic plains). By mid-century, annual average river runoff and water availability decrease by 10-30% over some dry regions at mid-latitudes. Freshwater availability in Central, South, East and South-East Asia, particularly in large river basins, is projected to decrease which, along with population growth and increasing demand, could adversely affect more than a billion people by the 2050s. Global reports indicate a loss of 10-40% in crop production by 2100 (Aggarwal et al., 2004, IPCC, 2007) [1,7] .

Climate change effects on: C3 and C4 plants

Photosynthesis increased to some extent in C 3 , but no significant response in C 4 . Elevated CO 2 increases leaf size, and this should increase leaf temperatures during heat stress more in C 3 than C 4 species, given the greater average stimulation of growth in elevated CO 2 in C 3 species. With increase in temperature (1 0 C), yield decreased from 3 -7% in C 3 plants such as wheat, soybean, mustard, groundnut, potato (Dagar et al., 2012) [4] . However, it is usually unaffected up to some extent since optimal temperature needed for C 4 photosynthesis is typically 10 °C greater than that of C 3 photosynthesis, however, Pn is usually inhibited when leaf temperatures exceed about 38 °C in maize Climate change effects on: Soil • Soil moisture stress enhanced due to evapotranspiration.

• Erosion in areas where winter rainfall becomes heavier.

• Drier soil will suppress both root growth and decomposition of organic matter. • High temperature could increase the rate of microbial decomposition of organic matter adversely affecting soil fertility in the long run. • Nutrient loss due to heavy rainfall in regions those are already moist.

Climate change effects on: Insects

Insects are cold-blooded organisms, therefore temperature is probably the single most important environmental factor influencing insect behaviour, distribution, development, survival, and reproduction. Plants grown under elevated CO 2 are less nutritious to insect herbivores, which can affect their behaviour and performance. As a consequence, insects have a more difficult time converting the food they eat into biomass. In order to mitigate the effects of less nutritious food, insect herbivores often consume more.

• In case of aphids a 2 °C temperatures increase causes one to five additional life cycles per season. (Yamamura and Kiritani, 1998) [22] • Winter mortality of adults of Nezara viridula (a) and Halyomorpha halys (b) is predicted to be reduced by 15% by each rise of 1°C and in Chilo suppressalis (c) two generation per year after 2°C warming. (Kiritani, 2006) [11] • Some insects are sensitive to precipitation and are killed or removed from crops by heavy rains, this consideration is important when choosing management options for onion thrips. (Reiners and Petzoldt, 2005) • The egg predator (Cyrtorhinus lividipennis) had increased instantaneous attack rates and decreased handling times with increasing temperatures until 32 °C. At 35 °C the attack rate and handling time decreased drastically. This implies that predator activity is likely to increase with increasing temperatures up to a critical temperature of about 35 °C. In addition to affecting biological characters, global warming may cause temporal asynchrony between interacting populations. (Song and Heong, 1997) [18] .

Climate change effects on Diseases

Generally high moisture and temperature favours and initiate disease development, as well as germination and proliferation of fungal spores of diverse pathogens (Agrios, 2005) [2] . Cereal crops become more susceptible to rust diseases because of temperature influence. Oat stem rust resistance genes Pg3 and Pg4 fail at temperature above 20 °C. Climate change is also reported to cause shift in the geographical distribution of host pathogens. Increase in temperature and UV radiation and decrease in moisture may render natural plant products, entomo-pathogenic viruses, fungi, bacteria and synthetic pesticides are less effective. High moisture favours foliar diseases and some soil borne pathogens such Phytophthora, Pythium, R. solaniand Sclerotium rolfsii. Drought stress affects the incidence and severity of viruses such as Maize dwarf mosaic virus (MDMV) and Beet yellows virus (BYV) (Clover et al., 1999) [3] . Dense canopy encouraged by higher CO 2 levels favours the incidence of rust, powdery mildew, Alternaria blight, Stemphylium blight and Anthracnose diseases. Moreover, higher CO 2 concentrations induce greater fungal spore production. Five basmati rice varieties were subjected to high thermal and low light stress (3 0 C higher than ambient temperature and 20% reduction in light intensity) during various growth phases to assess the effect of high temperature and low radiation on growth, yield and yield attributes of these varieties. High thermal and low light stress throughout the entire growth period (Tillering to maturity) caused highest reduction in grain yield followed by plant exposure to such stress from tillering to anthesis, while heat and low light stress from anthesis to maturity did not show any detrimental effect on grain yield. The reduction ingrain yield was mainly due to significant reduction in grains/panicle owing to marked increase in spikelet sterility under high temperature and low light stress as the number of panicles/pot and 1000 grain weight were least affected by such stress. www.extensionjournal.com Deepwater (floating) rice has three special adaptations • Ability to elongate with the rise of water levels.

• The upward bending of the terminal part of the plant called 'kneeing' that keeps the reproductive parts above. • Develop nodal tillers and roots from the upper nodes in the water.

Smart irrigation systems on WUE on wheat crop

Ghobari and Marazky (2014) [5] reported that in sprinkler irrigation systems, using smart irrigation system increases water use efficiency by 8.48%-15.76% over conventional sprinkler irrigation systems.

Effect of irrigation regimes at different crop stages on yield of wheat crop

Sharma et al., (1990) [17] observed that there was 166% increase in yield when wheat crop was irrigated at crown root initiation (CRI) stage over un-irrigated in 1986-87. Moreover, there was 571% increase when it was irrigated in all the 5 critical stages to that of un-irrigated.

Agro-techniques for adaptation to climate change: Nutrient management Usman (2013) [20] reported the interactive effects of phosphorus (P) and irrigation levels on water use efficiency (WUE) in rice. Significant and the highest mean water use efficiency (13.3 kg ha -1 mm -1 ) could be achieved when phosphorus was applied @150 kg ha -1 with 8 irrigations. However, there was declining trend for WUE under different of P level with increasing irrigation level. Interactions between different phosphorus levels and different irrigations regimes revealed that WUE increased with increase in P up to 150 kg ha -1 and diminished with further P supply under different of irrigation level.

Agro

References

1. Aggarwal PK, Joshi PK, Ingram JSI, Gupta RK. Adapting food systems of the Indo-Gangetic plains to global environmental change: key information needs to improve policy formulation. Environmental Science & Policy. 2004;7:487-498.
2. Agrios GN. Plant pathology. 5th ed. London: Elsevier; 2005:249-263.
3. Clover GRG, Smith HG, Azam-Ali SN, Jaggard KW. The effects of drought on sugar beet growth in isolation and in combination with Beet yellows virus infection. Journal of Agricultural Science. 1999;133:251-261.
4. Dagar JC, Singh AK, Rajbir S, Arunachalum A. Climate change vis-a-vis Indian agriculture. Annals of Agricultural Research New Series. 2012;33(4):189-203.
5. Ghobari HM, Marazky MSAE. Effect of smart sprinkler irrigation utilization on water use efficiency for wheat crops in arid regions. International Journal of Agricultural and Biological Engineering. 2014;7(1):2635.
6. Hundal SS, Kaur P. Climate change and its impact on crop productivity in Punjab, India. In: Abrol YP, Gadgil S, Pant GB, editors. Climate variability and agriculture. New Delhi: Narosa Publishing House; 1996:337-339.
7. IPCC. Summary for policymakers. In: Climate change: the physical science basis. Contribution of Working Group I to the fourth assessment report. Cambridge: Cambridge University Press; 2007.
8. Johnson TA, Singh S, Misra S, Kalpana S. Effect of elevated temperature and low radiation on growth and yield of basmati rice (Oryza sativa L.). Indian Journal of Plant Physiology. 2011;16(2):147-154.
9. Joshi A. Contingency crop planning for dryland areas in relation to climate change. Indian Journal of Agronomy. 2009;54(2):237-243.
10. Kalra N, Chakraborty D, Sharma A, Jommy M. Effect of increase in temperature on yield of some winter crops in northwest India. Current Science. 2008;94(1):82-88.
11. Kiritani K. Predicting impacts of global warming on population dynamics and distribution of arthropods in Japan. Population Ecology. 2006;48:5-12.
12. Lane A, Jarvis A. Changes in climate will modify the geography of crop suitability: agricultural biodiversity can help with adaptation. Paper presented at: ICRISAT/CGIAR 35th Anniversary Symposium; 2007 Nov 22-24;
13. Mathauda SS, Mavi HS, Bhangoo BS, Dhaliwal BK. Impact of projected climatic change on rice production in Punjab, India. Tropical Ecology. 2000;41:451-458.
14. Munich Reinsurance Company. Topics: annual review of natural catastrophes. Munich: Munich Reinsurance Company; 2002.
15. NATCOM. India's second national communication to the United Nations Framework Convention on Climate Change. New Delhi: Ministry of Environment and Forests, Government of India; 2012.
16. Saseendran SA, Singh KK, Rathore LS, Singh SV, Sinha SK. Effects of climate change on rice production in the tropical humid climate of Kerala, India. Climatic Change. 2000;44:495-514.
17. Sharma DK, Kumar A, Singh KN. Effect of irrigation scheduling on growth, yield and evapotranspiration of wheat on sodic soils. Agricultural Water Management. 1990;18:267-276.
18. Song YH, Heong KL. Changes in searching responses with temperature of Cyrtorhinus lividipennis on the eggs of the brown planthopper Nilaparvata lugens. Researches on Population Ecology. 1997;39(2):201206.
19. United Nations. World water development report 2018. 2018.
20. Usman K. Effect of phosphorus and irrigation levels on yield, water productivity, phosphorus use efficiency and income of lowland rice in northwest Pakistan. Rice Science. 2013;20(1):61-72.
21. Wada Y, Florke M, Hanasaki N, Eisner S, Fischer G, Tramberend S, et al. Modeling global water use for the 21st century: the Water Futures and Solutions initiative and its approaches. Geoscientific Model Development. 2016;9:175-222.
22. Yamamura K, Kiritani K. A simple method to estimate the potential increase in the number of generations under global warming in temperate zones. Applied Entomology and Zoology. 1998;33:289-298.