Anjali Kumari
Research Associate

Plant Pathology, ICAR Research complex for Eastern Region

Palandu, Ranchi, Pin Code 834001

Jharkhand, India

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Introduction

Climate change refers to the variation in the Earth’s global climate or in regional climate over time. It describes changes in the state of the atmosphere over time scales ranging from decades to millions of years.
In another way climate change is defined as “a change which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over comparable time periods”. The most imminent climatic changes in recent times is the increase in the atmospheric temperatures due to increased levels of greenhouse gases such as carbon dioxide (CO2), methane (CH4), ozone (O3), nitrous oxide (N2O) and chlorofluoro carbons (CFCs). Because of the increasing concentrations of those radioactive or greenhouse gases, there is much concern about future changes in our climate and direct or indirect effect on agriculture (Garg et al., 2001; IPCC, 2001; Krupa; 2003; Aggarwal, 2003; Bhatia et al., 2004).

Agriculture plays a key role in overall economic and social well being of India. Indian is an agricultural country, where 70 per cent population is dependent on agriculture. This forms the main source of income. The contribution of agriculture in the national income in India is more, hence, it is said that agriculture in India is a backbone of Indian Economy. The contribution from agriculture has been continuously falling from 55.1% in 1950-51 to 37.6% in 1981-82 & further to 18.5% in 2006-07. Agriculture constitutes about 75% of the total exports of the country. Such is the importance of agriculture as far as earnings of foreign exchange are concerned. Because of the heavy pressure of population in labor-surplus economies like India & its rapid increase the demand for food increases at a fast rate. Therefore, unless agriculture is able to continuously increase its surplus of food-grains, a crisis is likely to emerge. Agriculture provides raw materials to various industries of national importance. Sugar industry, Jute industry, Cotton textile industry, Vanaspati industry are examples of some such industries which depend on agriculture for their development. Since more than two-thirds of the population of India lives in rural areas, increased rural purchasing power is a valuable stimulus to industrial development. Climate change and agriculture are interrelated processes, both of which take place on a global scale. Thus seeing the importance of agriculture in Indian economy and livelihood, it is important to discuss the impact of climate change on agriculture for better understanding of the impact and to take preventive measures.

Effect of elevated temperature plays a major role on agriculture. On theoretical basis it can be expected that transpiration losses will increase with higher air temperatures. It is likely that the evaporative demand as determined by the vapour pressure deficit would increase by about 5 to 6% per degree warming (McKenney and Rosenberg, 1993). The overall effect of a higher temperature alone is an intensification of the hydrological cycle. It should be realized that the combined result of a higher ambient temperature, leading to a higher evaporative demand, and partial stomatal closure, counteracting this, could be overridden by changes in other environmental and atmospheric conditions like soil water availability, precipitation patterns, cloudiness and air humidity.

Effect of elevated CO2 on agriculture

Increases in leaf area and duration, leaf thickness, branching, tillering, stem and root length, and dry weight are well-known effects of increased CO2 on many plants. Based on a review of literature, Manning & von Tiedemann suggested that elevated CO2 would increase canopy size and density, resulting in a greater biomass of high nutritional quality. When combined with increased canopy humidity, this is likely to promote foliar diseases such as rusts, powdery mildew, leaf spot and blights. Increase in ambient CO2 concentration is beneficial since it leads to increased photosynthesis in several crops, especially those with C3 mechanism of photosynthesis such as wheat and rice, and decreased evaporative losses. Despite this, yields of major cereals crops, especially wheat are likely to be reduced due to decrease in grain filling duration, increased respiration, and /or reduction in rainfall/irrigation supplies. Increase in extreme weather events such as floods, droughts, cyclones and heat waves will adversely affect agricultural productivity. Reduction in yields in the rainfed areas due to changes in rainfall pattern during monsoon season and increased crop water demand. Incidence of cold waves and frost events may decrease in future due to global warming and it would lead to a decreased probability of yield loss associated with frost damage in northern India in crops such as mustard and vegetables. Quality of fruits, vegetables, tea, coffee, aromatic, and medicinal plants may be affected. Incidence of pest and diseases of crops to be altered because of more enhanced pathogen and vector development, rapid pathogen transmission and increased host susceptibility. Agricultural biodiversity is also threatened due to the decrease in rainfall and increase in temperature, sea level rise, and increased frequency and severity of droughts, cyclones and floods.

Impact of climate change on management practices

In recent times, the crop simulation models have been used extensively to study the impact of climate change on agricultural production and food security. The output provided by the simulation models can be used to make appropriate crop management decisions and to provide farmers and others with alternative options for their farming system(Mall et al., 2006) Assist farmers in coping with current climatic risks(weather services, agro-advisories, insurance, community banks for seed and fodder). Intensify food production systems (technology and input delivery systems, market links) Improve land and water management(technologies for resource conservation and use efficiency) Enable policies and regional cooperation (incentives to farmers for resource conservation and use efficiency, pricing of resources, credit for transition to adaptation technologies) Strengthen research for enhancing adaptive capacity varieties, resource conservation technologies, pest surveillance -for improved assessments: mechanism for collection and dissemination of weather, soil, water and agricultural data. We have to reduce our greenhouse gas emissions and shift towards becoming a low carbon economy – one that relies on low emissions forms of energy and that is much more efficient in using energy resources.

Conclusion

Climate change is the major issue of recent times. It is perhaps, the greatest challenge to sustainable development. Attri and Rathore (2003) suggested the adaptation strategies for sustainable production of wheat and ensuring food security. Climate change is real and underway, so there is a need of impact identification and adoption to cope with vulnerabilities in agricultural sector. Climate change is likely to reduce yields of most crops in long-term. In short-term effects may be small (preliminary results, better field data and models needed). 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.