By US Saikia & B Goswami
Climate change refers to the changes in the average state of the atmosphere over time scales ranging from decades to millions of years in regional or global scale. Though climate change is a natural phenomenon, the current climate change is taking place at a very rapid pace and that is the main issue of concern. The signs of adverse affects of climate change are increasingly becoming evident and agriculture is one of the major sectors, which is struggling to adjust with such rapid changes. The biological system has its inherent capacity to adjust itself to the changes in the external environment. But, it is a time taking process and hence, the rapid climate change is creating worldwide threat to both floral and faunal diversity apart from creating severe threat to global food security.
Global and India scenarios of climate change
Every year, humanity releases 8 billion tons CO2 to atmosphere (6.5 billion tons from fossil fuels & 1.5 billion tons due to deforestation). Nearly, 50 % (3.2 billion tons of CO2) remains in the atmosphere to warm up the planet. In 2013, the CO2 concentration has reached its highest level i.e. 401 ppm compared to 280 ppm in 1750. As a result, the global temperature is likely to rise by 1.4-5.8°C during the 21st century; with rise in sea level by 0.09-0.88 m. Variation in climatic pattern has been witnessed with frequent occurrence of drought, flood, cyclone, extended and untimely snowfall etc.
Researchers have found non uniform variation of climate change in India. If, some area is witnessing increase in rainfall (West coast, northern AP and NW India), opposite is happening in some other areas (eg. NE India and eastern MP). India witnessed increase in surface air temperature by 0.51 0C during 1901-2007 and the average temperature has risen by 0.2 0C per decade during 1971-2009. Deglaciation in the Himalayas and sea level rise in Indian Ocean @1.63 mm/year during 1993-2009 are other noticeable changes recorded as a result of rapid climate change in India.
Causes of climate change
There are different views on causes of rapid climate change. But, in general, the causes of the change may be categorized in to two broad categories, viz., Natural (volcanoes, ocean current, sunspot cycle & solar flare etc.) and Anthropogenic/manmade factors (change in land use pattern, burning of fossil fuel leading to increasing concentration of GHG’s, industrialization, urbanization and deforestation). These factors are gaining importance mainly since the industrial revolution got started in the western countries.
Consequences of climate change
Weather/climate is the driving force for success or failure of cropping/farming systems. Climate change is likely to have both positive and negative consequences. The positive one is that increasing concentration of CO2 will lead to high rate of photosynthesis, mostly in C3 plant like rice. The temperate regions of the world may be able to grow tropical crops due to increasing atmospheric temperature. But, increasing cloudiness is likely to reduce appropriate solar insolation leading to poor yield realization. Further, high temperature during the reproductive stage may adversely affect the dry-matter partitioning by reducing rate of net photosynthesis. In India, wheat crop is frequently facing the intense heat wave condition during its grain filling and ripening period (March-April) impacting wheat productivity very adversely. Besides, frequent droughts, floods, heat/cold waves, cyclones etc. have become more destructive impacting the economy as a whole. New pathogens & insects are likely to emerge due to climate change. In India, increasing sea & river water temperature are likely to affect fish breeding, migration and harvests. Human migration across political boundaries due to fall out of climate change is also one of the greatly debated serious consequences of the current time.
Climate change trends in North East India
The NE region has a mean minimum/maximum summer season temperature of 23/31 0C and 9/24 0C during winter. It receives an average 1000-2000 mm of rainfall during the summer and about 200 mm during winter. Under changing climate the projected increase in minimum and maximum temperature in NE Region, during summer, is about 2 0C by 2030. The summer rainfall is also likely to reduce by about 10%. On the other hand, during winter projected increase in temperature is about 2.5 0C and remains rainless mostly.
Although the contribution from agriculture sector towards gross domestic product has declined, yet it remains the predominant sector for Indian economy. Over 75% of the people of the NE India directly depend on agriculture for their livelihood. Therefore, better performance of agriculture has a direct and multiplier effect across the economy of the region. Because of climate change the rain-fed agriculture is facing a greater risk as it is resource poor and having limited flexibility for adaptation. Under changing scenarios there is increase in demand for fresh water and nutrient requirement, increase in soil erosion & nutrient losses affecting soil health, intensification of pest, disease and weed problems, reduction in nutritional quality and low input use efficiency.
A study done at ICAR, Umiam has reveled that, the average monsoon rainfall/rainy days in NE region has decreased from 900-3000 mm/65-91 days (1951-90) to 850-2350 mm/57-85 days (1991-07). Significant decrease in rainfall is noticed in Ukhrul and Senapati districts of Manipur and Phek, Zunheboto and Wokha districts of Nagaland. The reduction in rainy days is highly significant for all the districts of Nagaland; upper Assam districts of Tinsukia, Dibrugarh; and Tirap, Changlang, Lower Dibang valley districts of Arunachal Pradesh. This is resulting in early/mid/late season water stress and reduction in crop yield.
Role of decision support systems in adaptation & mitigation
According to the agricultural experts sustainable livelihood could be achieved by harnessing local resources available in a given agro?climatic situation. In general, adaptation in rain-fed agriculture may be brought about by introduction of improved climate resilient cultivars, modifying existing cropping pattern and diversification, rational irrigation and resource conservation technologies. Increasing scientific and social awareness among the farmers to educate and prepare them to face the consequences of climate change is an integral part of overall adaptation strategy. Easy access to inputs, markets, microfinance and insurance facilities are other key terms of such policies.
Growth and development of biological world is highly regulated by the atmospheric forces. Being an agricultural scientist, one always likes to know how different processes in a living system are regulated by the environmental forces, eg. germination through flowering up to maturity and eventual dying in plants. The outcome of such exploration has led to discovery of various complex processes like photosynthesis and respiration etc. For easy understanding of a system scientists have quantified each individual process, transform them into some logical mathematical expressions. These processes are systematically arranged and linked to each other as well as to the external factors, to mimic a complete real system. This has led to the beginning of crop growth simulation models. Simulation is mimicking of a real world system in a virtual environment. This is an improved tool to understand the functioning of a plant in the computer with the same precision as if it has been grown actually in the field. There is a host of crop growth simulation models developed for different crops including rice, maize, wheat, legumes, oilseeds, vegetables etc. A number of such individual models are embedded in a single platform for easy imposition/testing of various management and environmental conditions on the growing environment, and it facilitates the process of decision making by the user groups. Examples of commonly used such platforms are DSSAT, InfoCrop, AquaCrop etc. These are also called ‘Decision support systems’.
Applications of crop simulation models are numerous. Accuracy of model prediction depends on the precision taken in assumption and experimentation. Calibration of any model with respect to selective cultivar and climatic condition followed by validation are to be carried out before taking up any application of the same. As developing a simulation model involves lot of expertise, time and cost, one need to calibrate the existing models in line with his location, crops and climate. A simulation study done with DSSAT model has envisaged that upland rice productivity in Meghalaya is likely to increase by 5-7% by 2020 if maximum temperature increased by 2 0C and level of CO2 reached 450 ppm. With increasing risks involved in farming is brought about by climate change, the modeling approach is likely to play a major role in assessing the vulnerability of existing agricultural systems, both in irrigated and rainfed environments. Most of these models are equipped with provisions to impose/create extreme conditions of weather- eg. change in rainfall pattern, extreme rainfall, high/low temperature during critical growth stages, flood/drought etc. It is also possible to track the growth and development processes by incorporating real time weather data on day to day basis. We can find out most suitable crop, cultivar, sowing window, fertilizer application options either for a single crop or crops in succession. Regulated and judicious application of irrigation water helps to enhance water productivity. Hence, crop growth simulation models may be used effectively to evolve strategies of suitable adaptation to climate change through changes in farming practices, and cropping patterns, which may, in turn, help to ease out the impact of climate change on the farming community.
(The writers are scientists at ICAR Research Complex for NEH Region, Umiam, Meghalaya)