Effect of Global Warming on Agricultural Systems

Transcription

1 American-Eurasian J. Agric. & Environ. Sci., 13 (5): , 2013 ISSN IDOSI Publications, 2013 DOI: /idosi.aejaes Effect of Global Warming on Agricultural Systems Rajani Srivastava Environmental, Science and Technology, Institute of Environment and Sustainable, Development Banaras, Hindu University, Varanasi , India Abstract: Climate change and agriculture are interrelated processes, both of which take place on a global scale. The overall effect of climate change on agriculture will depend on the balance of these effects. Due to global warming, the frequency of droughts in several tropical countries has increased whereas flooding in several countries severely disrupted the food production and the carrying capacity of the biosphere. Assessment of the effects of global climate changes on agriculture might help to properly anticipate and adapt farming to maximize agricultural production. This paper emphasizes how agricultural growth and sustainability has to be achieved,while coping with the climate change phenomenon. Climate change is likely to reduce yields of most crops in long-term. In short-term effects may be small. Increased climatic variability could cause significant fluctuations in production even in short-term. Adaptation strategies can help minimize negative impacts. These need greater research, policy and financial support Key words: Climate change Global warming Agriculture India Adaptation INTRODUCTION st One of the most important challenges of the 21 century is climate change [1]. Climate change is defined as change in climate over time, whether due to natural variability or as a result of human activity. Climate change and agriculture are closely related processes and response of climate change in developed and developing countries varies greatly. The most important climatic change in recent times is increased levels of greenhouse gases such as carbon dioxide, methane, ozone, nitrous oxide and chlorofluoro carbons. Global warming (i.e. increased greenhouse gases) is projected to have significant impacts on conditions affecting agriculture, including increased global mean surface temperature, glacial run-off, precipitation and the interaction of these elements. The overall effect of climate change on agriculture will depend on the balance of these effects. Due to global warming, the frequency of droughts in several tropical countries has increased whereas flooding in several countries severely disrupted the food production and the carrying capacity of the biosphere. Thus, there is much concern about future climate changes and its direct or indirect effect on agriculture [2-5]. Changes in global supply and demand for climate change phenomenon, various crops provide new challenges to farmers worldwide. There are no hard facts about what will definitely be the result of increase in the concentration of greenhouse gases within the atmosphere and no firm time scales are known. Agriculture is an important sector to consider in terms of climate change. This paper attempts to take an overview of the impacts of climate change on agricultural systems. It also emphasizes how agricultural growth and sustainability has to be achieved while coping with the climate change phenomenon. Agriculture and Climate: Agriculture plays the key role in economy and provides food and livelihood activities to much of the countries population. While, the magnitude of impact varies greatly by region and climate change is expected to impact on agricultural productivity and shifting crop patterns. Agricultural facilities contribute approximately 20% of the annual increase in Corresponding Author: Rajani Srivastava, Environmental, Science and Technology, Institute of Environment and Sustainable Development, Banaras, Hindu University, Varanasi , India. Mob:

2 anthropogenic greenhouse gas emissions [6]. The 20-30% in the tropical and subtropical areas due to greenhouse gases allow the transmission of light reaching projected temperature rise. Tropical countries are likely to the earth; they block the transmission of heat (infra-red be affected more compared the countries situated in radiation) trying to escape from the atmosphere, thus temperate regions [16]. The brunt of environmental trapping the heat as in a greenhouse. CH4 has changes is expected to be very high in India due to approximately 300 times more potential of global warming greater dependence on agriculture, limited natural than CO 2 and about 20 times that of N O. 2 The main resources, alarming increase in human and livestock sources are nitrogen fertilizers, flooded rice fields, soil population, changing pattern in land use and management, land conversion, biomass burning and socio-economic factors that pose a great threat in meeting livestock production and associated manure management the food, fibre, fuel and fodder requirement. There is a [7]. Of the total greenhouse gases emitted in the likelihood of a considerable impact on agricultural landatmosphere, CO2contributes approximately 72%, followed use due to snow melt, availability of irrigation, frequency by CH 4(18%) and N2O (9%). The major source of releases and intensity of inter- and intra- seasonal droughts and of CH4 is first paddy fields (91%) than from animal floods, soil organic transformation matters, soil erosion husbandry (7%) and the burning of agricultural wastes and availability of energy as a consequence of global (2%). About 80% of the global CH 4 emissions come from warming, impacting agricultural production and hence, the buffalo, cattle and domestic livestock annually. Most of nations food security (Fig. 1). Global warming due to the agriculture-based N2O emissions come from nitrogen greenhouse effect is expected to impact hydrological fertilizer usage, legume cropping and animal waste (62%) cycle viz. precipitation, evapo-transpiration, soil moisture whereas small amount of N2O are also released during etc., which would pose new challenges for agriculture biomass burning (26%) [8]. However, the N2O emitted is [17,18,19]. much lower in volume than the amount of CH 4. Agriculture plays an important role in Indian economy [20, 21,22]. About 700 million of its rural Indian Scenario: In developing countries like India, population (over 60% of our labour force) depends several studies have been conducted to assess the directly on climate-sensitive sectors such as agriculture, impact of increased global atmospheric concentration forests and fisheries and natural resources for their of CO 2 and other green house gases like methane, subsistence and livelihoods. nitrous oxide on agriculture [4]. There are several models Climate change is impacting all the natural for same crop are now available that can be employed ecosystems as well as socio-economic systems of the for impact assessment of climate change [9]. The climate country. Climate change will have major impact on Indian sensitivity of agriculture has been measured by various agriculture. In India, average food consumption at present methods like agronomic analysis model and agro is 550g per capita per day whereas the corresponding ecological zone modeling or by cross sectional analysis figures in China and USA are 980g and 2850g respectively method. In major crops, most farm performance is [23,17]. Present annual requirement based on present measured by cross sectional analysis in different climate consumption level (550g) for the country, is about 210 zones. Million Tonnes (Mt), which is almost equal to the current Some studies have showed that CO2 concentration production. Therefore, agricultural sector in India needs was increasing from 280 ppm pre industrial period (1850) to be improved steadily on sustainable basis. India needs to 379 ppm in 2005 means since then it was rising at the to prepare in advance to face the consequences of climate rate of 1.5 to 1.8 ppm per year. It is assumed that CO2 is change. Although, the effect of increasing CO2 st likely to be doubled by the end of 21 century [10]. It was concentrations will increase the net primary productivity shown by Kimball [11] and Uprety [12] that elevated CO2 of plants, but climate changes and the changes in result into increased photosynthetic rate and crop yield. disturbance regimes associated with them, may lead either Uprety et al. [13] increase in rice grain yield due to to increased or decreased net ecosystem productivity. In increase in CO 2 concentration. While, some studies have many tropical and subtropical regions, potential yields are pointed out that higher temperature during the growing projected to decrease for most projected increases in season, the harvest of maize, rice and other stable crops temperature and these can have tremendous impact on could drop by up to 40% by the end of this century [14,15,16]. Crop yields could be reduced by as much as 678

3 Changes in green house gases Climate Change (Global warming) Direct effects on crop Physiology e.g. photosysnthesis) Phenology e.g. flowering time) Morphology (e.g. leaf area) Indirect effects Soil fertility Irrigation availability Pests incidence & vulnerability Floods & Droughts Socio-economics Food demand Costs & benefits Policy Land use change Trade Human intervention Adaptation Policy planning Agricultural production & Vulnerability Fig. 1: Assessment of climate change on agriculture vulnerability agricultural production and hence, food security of any maximum increase over northern India. The warming is region [4]. The rising temperatures and carbon dioxide and also projected to be relatively greater in winter and postuncertainties in rainfall associated with global warming monsoon seasons. may or may not have serious direct and indirect Although increase in carbon dioxide is likely to be consequences on crop production. It is, therefore, beneficial to several crops, associated increase in important to have an assessment of the direct and indirect temperatures and increased variability of rainfall would consequences of global warming on different crops considerably impact food production. Recent IPCC report especially on cereals contributing to the food security and a few other global studies indicate a probability of [21,24, 25] % loss in crop production in India with increases in temperature by There are a few Indian studies Future Projections: It is projected that by the end of the on this theme and they generally confirm similar trend of 21st century rainfall will increase by 15-31% and the mean agricultural decline with climate change [15,17]. Recent annual temperature will increase by 3 C to 6 C [26]. The studies done at the Indian Agricultural Research Institute warming is more pronounced over land areas, with the indicate the possibility of loss of 4 5 million tons in wheat 679

4 production in future with every rise of 1 C temperature and taking advantage of the beneficial effects of changes throughout the growing period (but no adaptation in climate [27,30]. The extent of these adaptations benefits). It is, however, possible for farmers and other depends on the affordability of such measures, stakeholders to adapt to a limited extent and reduce the particularly in developing countries in the world. Recent losses. Simple adaptations such as change in planting studies show that the increase costs of agricultural dates and crop varieties could help in reducing impacts of production under climate change scenarios would be a climate change to some extent [27]. Increasing climatic serious economic burden for some developing countries. variability associated with global warming will, Other important factors will be access to know-how and nevertheless, result in considerable seasonal/annual technology, the rate of climate change and biophysical fluctuations in food production [15,28]. All agricultural constraints such as soil characteristics, crop genetics and commodities even today are sensitive to such variability. water availability [31]. Droughts, floods, tropical cyclones, heavy precipitation The main problem associated is the uncertainty events, hot extremes and heat waves are known to surrounding the effects of climate change and the negatively impact agricultural production and farmers unknown time frames. It is still uncertain who will be most livelihood. The projected increase in these events will impacted by the changes and this fosters a lack of result in greater instability in food production and initiative for taking action now to mitigate the effects of threaten livelihood security of farmers. Increasing glacier climate. There will be both positive and negative effect of melt in Himalayas will affect availability of irrigation climate change; some areas of world are beneficiary in especially in the Indo-Gangetic plains, which, in turn, has agricultural production while other areas show reverse. large consequences on our food production. Small Economic indicator (like crop production, income and risk) changes in temperature and rainfall could have significant and environmental indicator (like ground water level, land effect on quality of cereals, fruits, aromatic and medicinal degradation and biodiversity) is the part of sustainability. plants with resultant implications on their prices and This reinforces the need to determine the magnitude of trade. Pathogens and insect populations are strongly warming which may accompany the CO 2 buildup currently dependent upon temperature and humidity. Increases in under way in the atmosphere [32]. Thus, immediate these parameters will change their population dynamics attention is needed. resulting in yield loss. Global warming could increase water, shelter and Needs for Future Researsh: Due to the complex energy requirement of livestock for meeting projected milk interaction of climate impacts, combined with varying demands. Increasing sea and river water temperature is irrigation techniques, regional factors and differences in likely to affect fish breeding, migration and harvests. A crops, the detailed impacts of these factors need to be rise in temperature as small as 1 C could have important investigated further. Further research may include the and rapid effects on the mortality of fish and their things like precision in climate change prediction with geographical distributions [29]. Corals in Indian Ocean higher resolution on spatial and temporal scales and will be soon exposed to summer temperatures that will linking of predictions with agricultural production exceed the thermal thresholds observed over the last 20 systems to suggest suitable options for sustaining years. Annual bleaching of corals will become almost a agricultural production. There is need to prepare a certainty from database on climate change impacts on agriculture in selected locations and development of models for pest Reduction of Green House Gases: How to prepare for population dynamics. future climate change? This is a major question before agronomist, ecologist and policy makers. The possible CONCLUSION answer is the ability to adjust the changes by adopting alternate farming practices. Adaptation, such as changes Climate change is likely to reduce yields of most in crops and crop varieties, improved water management crops in long-term. In short-term effects may be small. and irrigation systems, breeding of plants that are more Increased climatic variability could cause significant resilient to variability of climate and changes in planting fluctuations in production even in short-term. Adaptation schedules like changes in sowing dates and tillage strategies can help minimize negative impacts. These need practices will be important in limiting the negative effects greater research, policy and financial support. 680

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