S. K. Guru
1.4 Climate change impacts
Climate change will have a profound impact on human and ecosystems during the coming decades through variations in global average temperature and rainfall (Anonymous 2001a, d,e). The temperature of the temperate and polar regions will increase (Wittwer, 1990), decreasing the snowing period (Seino, 1995); thereby increasing the length and intensity of growing periods (Wittwer, 1980; Decker et al., 1985) and growing degree units (Rosenzweig, 1985). The consequences include melting glaciers, sinking of oceans, more precipitation, more and more extreme and unpredicted weather events, shift- ing seasons, increasing incidences and resurgence of pests, weeds and diseases (Chakravarty and Mallick, 2003; Goulder and Pizer, 2006; Ninan and Bedamatta, 2012). Tropical coun- tries are likely to be affected more than the countries in the temperate regions (Anonymous, 2007a,b). Climate change poses unprecedented challenges to human society and ecosys- tems in the twenty-first century, particularly in the developing nation in the tropics (Parry, 1990; Parry et al., 1992, 2004, 2005; McCarthy et al., 2001). The accelerating pace of climate change combined with global population and income growth threatens food security (Nelson et al., 2009). It will also affect livelihoods and human well-being (Ninan and Bedamatta, 2012). Populations in the developing world which are already vulnerable and food insecure are likely to be more seriously affected.
The impact of climate change will persist. This will affect the basic elements of life around the world such as access to water, food production, healthcare and the environment (Ninan and Bedamatta, 2012). Millions of people could suffer from hunger, water shortage and coastal flooding as the world gets warmer. The overall costs and risks of climate change are expected to be equivalent to losing at least 5% of global GDP each year, if we do not act now. If a wider range of risks is taken into account, the estimated damage could rise to 20% of GDP or more (Stern, 2006, 2007). There are certain regions, sec- tors, ecosystems and social groups which will be affected the most by climate change and the consequences of economic glo- balisation. Managing the impact of climate change, therefore,
poses a challenge to governments and societies (Ninan and Bedamatta, 2012).
In 2005, nearly half of the economically active population in developing countries (2.5 billion) relied on agriculture for its livelihood (Nelson et al., 2009). Today three-fourths of the world’s poor population live in rural areas (Anonymous, 2008b).
Agriculture and allied sectors are highly sensitive and vulner- able to climate change (Adams et al., 1998) as these changes will have an impact on agriculture by affecting crops, soil, live- stock, fisheries and pests, directly and indirectly (Anonymous, 2007b; Ninan and Bedamatta, 2012). Global warming due to the greenhouse effect is expected to affect the hydrological cycle namely, precipitation, evapotranspiration and soil mois- ture, which will pose new challenges for agriculture. The Food Policy Report 2009 suggested that agriculture and human well- being will be negatively affected by climate change (Nelson et al., 2009) and summarises the following impact:
• In developing countries, climate change will cause yield declines for the most important crops. South Asia will be particularly hard hit.
• Climate change will have varying effects on irrigated yields across regions, but irrigated yields for all crops in South Asia will experience large declines.
• Climate change will result in additional price increases for the most important agricultural crops such as rice, wheat, maize and soya beans. Higher feed prices will result in higher meat prices. As a result, climate change will reduce the growth in meat consumption slightly and cause a more substantial fall in cereals consumption.
• Calorie availability in 2050 will not only be lower than in the no-climate-change scenario. It will actually decline relative to 2000 levels throughout the developing world.
• By 2050, the decline in calorie availability will increase child malnutrition by 20%, relative to a world with no cli- mate change. Climate change will eliminate much of the improvement in child malnourishment levels that would occur with no climate change.
• Thus, aggressive agricultural productivity investments of US$ 7.1–7.3 billion are needed to raise calorie con- sumption enough to offset the negative impacts of climate change on the health and well-being of children.
The brunt of environmental changes on India is expected to be very high due to greater dependence on agriculture, limited
natural resources, alarming increase in human and livestock population, changing patterns in land use and socio-economic factors that pose a great threat in meeting the growing food, fibre, fuel and fodder requirements (Ninan and Bedamatta, 2012). Droughts, floods, tropical cyclones, heavy precipitation events, hot extremes and heat waves are known to impact agri- cultural production and farmer’s livelihood negatively as all agricultural commodities even today are sensitive to such vari- ability. Increasing glacier melt in the Himalayas will change the availability of irrigation especially in the Indo-Gangetic plains affecting food production. Further warming is likely to lead to a loss of 1.6 million tonnes of milk production in India by 2020 (Ninan and Bedamatta, 2012). Total farm-level net-revenue loss of 8.4–25% is projected for the country in an event of 2°C temperature rise along with a 7% precipitation increase, which will amount to a loss of *`81–195 billion (Kavi Kumar and Parikh, 1998, 2001a; Sanghi et al., 1998; Kavi Kumar, 2009).
Globally Climate and climatic resources change can affect agriculture of both developing and developed countries in a variety of ways (Downing, 1996; Watson et al., 1996; Cline, 2008). Climate change and agriculture are interrelated pro- cesses, both of which takes place on a global scale (Anonymous, 2007c). Climate change is projected to have significant impacts on conditions affecting crop and livestock production, includ- ing temperature, carbon dioxide, glacial run-off, precipitation hydrologic balances, input supplies, other components of agri- cultural systems and the interaction of these elements (Adams et al., 1998; Webster, 2008; Gornall et al., 2010). For example, crop and livestock yields are directly affected by changes in cli- matic factors such as temperature and precipitation and the fre- quency and severity of extreme events such as droughts, floods and wind storms/tropical cyclones. Beyond a certain range of temperatures, warming tends to reduce yields because crops speed through their development, producing less grain in the process. It was estimated that warming since 1981 has resulted in annual combined yield losses of 40 million tonnes or US $5 billion (Lobell and Field, 2007).
Higher temperatures also interfere with the ability of plants to get and use moisture. Evaporation from the soil acceler- ates when temperatures rise and plants increase transpiration.
These conditions determine the carrying capacity of the bio- sphere to produce enough food for the human population and domesticated animals. Despite technological advances such as Impacts on
agriculture
improved varieties, genetically modified organisms and irriga- tion systems, weather is still a key factor in agricultural produc- tivity, as well as soil properties and natural communities (Curry et al., 1990; Curtis and Wang, 1998). The effect of climate on agriculture is related to variabilities in local climates rather than in global climate patterns (Kaufmann and Snell, 1997;
Freckleton et al., 1999; Gadgil et al., 1999; Tan and Shibasaki, 2006). The international aspect of trade and security in terms of food implies the need to also consider the effects of climate change on a global scale. The poorest countries would be hard- est hit with reductions in crop yields mostly in tropical and sub- tropical regions due to decreased water availability and new or changed insect pest incidence (Anonymous, 2001a,b; Cline, 2007, 2008). Marine life and the fishing industry will also be severely affected in some places. Climate change induced by increasing GHGs is likely to affect crops differently from region to region. A decrease in potential yields is likely to be caused by the shortening growth period, decreases in water availability and poor vernalisation. Climatic change would affect agriculture in several ways as
• Productivity, in terms of quantity and quality of crops
• Agricultural practices through changes of water use (irri- gation) and agricultural inputs such as herbicides, insec- ticides and fertilisers
• Environmental effects relating to frequency and intensity of soil drainage (leading to nitrogen leaching), soil ero- sion, reduction of crop diversity
• Rural space through the loss and gain of cultivated lands, land speculation, land renunciation and hydraulic amenities
• Adaptation, that is, organisms may become more or less competitive, as well as humans’ urgency to develop more competitive organisms, such as flood-resistant or salt- resistant varieties of rice.
The possible changes to climate and atmosphere in the com- ing decades may influence GHG emissions from agriculture and the effectiveness of practices adopted to minimise those (Smith et al., 2007a). The concentration of CO2 is projected to double within the next century. This will influence the plant growth rates, plant litter composition, drought tolerance and nitrogen demands (Torbert et al., 2000; Norby et al., 2001; Jensen and Christensen, 2004; Henry et al., 2005; Van Groenigen et al., 2005; Long et al., 2006). Increasing temperatures may not
only increase crop production in colder regions due to a longer growing season (Smith et al., 2005a,b) but also could accelerate decomposition of soil organic matter, releasing stored soil car- bon into the atmosphere (Fang et al., 2005; Knorr et al., 2005;
Smith et al., 2005b). Moreover, changes in precipitation pat- terns could change the adaptability of crops or cropping sys- tems selected to reduce GHG emissions (Smith et al., 2007a).
Agriculture will have a two-sided effect: an increased CO2
climate change, first, directly by the fertilising effect creating a higher level of ambient CO2 (both positively and negatively) in the atmosphere and, second, indirectly by the effect of change in climate on crop, livestock, insect pests, diseases, weeds, soils and water supplies (Easterling et al., 1989; Parry et al., 1989, 1990). These impacts classified as both direct (positive and negative) and indirect are listed in Tables 1.1 through 1.3.
The effects of climate change on agriculture vary by region and by crop (Adams et al., 1998). Higher growing season tem- peratures can significantly impact agricultural productivity, farm incomes and food security (Battisti and Naylor, 2009).
In mid and high latitudes, the suitability and productivity of table 1.1 Positive impacts on agriculture
S. no. Evidence of climate change
Impact on agricultural production
1 Longer frost-free periods Use of higher-yielding genetics
2 Lower daily maximum temperature in summer
Reduced plant stress 3 More freeze/thaw cycles in
winter
Increased soil tilt and water infiltration 4 More summer precipitation Reduced plant stress 5 More soil moisture Reduced plant stress 6 Higher dew point temperatures Reduced moisture stress 7 Higher intensity of solar output Increased degree days 8 More diffuse light (increased
cloudiness)
Reduced plant stress 9 Higher water-use efficiency Higher yields 10 Warmer spring soil
temperatures
Use of higher-yielding genetics
11 Reduced risk of late spring or early fall frosts
Use of higher-yielding genetics
12 Increased atmospheric CO2
levels
Increased photosynthesis and yields
crops are projected to increase and extend northwards, espe- cially for cereals and cool season seed crops (Maracchi et al., 2005; Tuck et al., 2006). Crops prevalent in southern Europe such as maize, sunflower and soya beans could also become viable further north and at higher altitudes (Hildén et al., 2005;
Audsley et al., 2006). Here, yields could increase by as much as 30% by the 2050s, depending on the crop (Alexandrov et al., 2002; Ewert et al., 2005; Richter and Semenov, 2005; Audsley et al., 2006). Large gains in potential agricultural land was pro- jected for the Russian Federation in the coming century (64%
increase over 245 million hectares by the 2080s) due to its table 1.2 Negative impacts on agriculture
S. no. Evidence of climate change Impact on agricultural production 1 More spring precipitation causes
water logging of soils
Delay planting, reduced yields, compaction, change to lower-yielding genetics
2 Higher humidity promotes disease and fungus
Yield loss, increased remediation costs 3 Higher night-time temperatures in
summer
Plant stress and yield loss 4 More intense rain events at the
beginning of crop cycle
Re-planting and field maintenance costs;
loss of soil productivity and soil carbon 5 More droughts Yield loss; stress on livestock; increase in
irrigation costs; increased costs to bring feed and water to livestock
6 More floods Re-planting costs, loss of soil productivity and soil carbon; damage to infrastructure and logistics
7 More over-wintering of pests due to warmer winter low temperature
Yield loss, increased remediation costs 8 More vigorous weed growth due to
temperature, precipitation and CO2 changes
Yield loss, increased remediation costs
9 Summer time heat stress on livestock
Productivity loss, increase in miscarriages, may restrict cows on pasture
10 Temperature changes increase disease among pollinators
Losses to cropping (forage, fruits, vegetables) systems
11 Increased taxes or regulations on energy-dependent inputs to agriculture (e.g. nitrogen fertiliser)
Profitability impacts on producers; loss of small-scale farm supply dealers
12 New diseases or re-emergence of diseases that had been eradicated or under control
Enlarged spread pattern, diffusion range and amplification of animal diseases
longer planting windows and generally more favourable grow- ing conditions under warming (Fischer et al., 2005). However, technological developments could outweigh these effects, resulting in combined wheat yield increases of 37–101% by the 2050s (Ewert et al., 2005).
A record crop yield loss of 36% occurred in Italy for corn grown in the Po valley where extremely high temperatures pre- vailed (Ciais et al., 2005). It is estimated that such summer temperatures in Europe are now 50% more likely to occur as a result of anthropogenic climate change (Stott et al., 2004). In areas where temperatures are already close to the physiologi- cal maxima for crops such as seasonally arid and tropical regions, higher temperatures may be more immediately det- rimental, increasing the heat stress on crops and water loss by evaporation (Gornall et al., 2010). A 2°C local warming in the mid latitudes could increase wheat production by nearly 10%, whereas at low latitudes the same amount of warming may decrease yields by nearly the same amount. Different crops show different sensitivities to warming. It is important to note the large uncertainties in crop yield changes for a given level of warming.
table 1.3 Indirect impacts on agriculture
S. no. Situational change Impact on agriculture 1 Regulation involving greenhouse
gas emissions
Potential increased costs to meet new regulations; opportunities to participate in new carbon markets and increase profits 2 Litigation from damages due to
extreme events or management of carbon markets
Legal costs may increase
3 New weed and pest species migration
Control strategies will have to be developed;
increased pest management costs as well as crop losses
4 Vigorous weed growth results in increased herbicide use
Increase in resistance or reduction in time to development of resistance; regulatory compliance costs or litigation over off-site damages from pesticides
5 Possibility of increased inter-annual variability of weather patterns
Increased risk in crop rotation, genetic selection and marketing decisions 6 Increased global demand for food
production due to climate and demographic changes
New markets; increase in intensification of production; increase in absentee ownership 7 Increased period for forage
production
Decreased need for large forage storage across winter for livestock operations
Water is vital to plant growth, so varying precipitation pat- terns forcing a northward advance of monsoon rainfall further into Africa and Asia, increasing the occurrence of total rainfall, will have a significant impact on agriculture (Parry et al., 1988, 1989; Wittwer, 1990). This rainfall will also be more intense in its occurrence and therefore will propagate flooding and ero- sion. Food production can also be impacted by too much water (Gornall et al., 2010). Heavy rainfall events leading to flooding can wipe out entire crops over wide areas and excess water can also lead to other impacts, including soil water logging, anaer- obicity and reduced plant growth. Indirect impacts include delayed farming operations. Agricultural machinery may not be adapted to wet soil conditions. The proportion of total rain falling in heavy rainfall events appears to be increasing and this trend is expected to continue as the climate continues to warm. A doubling of CO2 is projected to lead to an increase in intense rainfall over much of Europe. In the higher end projec- tions, rainfall intensity increases by over 25% in many areas important for agriculture. As over 80% of total agriculture is rain-fed, projections of future precipitation changes often influ- ence the magnitude and direction of climate impacts on crop production (Olesen and Bindi, 2002; Tubiello et al., 2002). The impact of global warming on regional precipitation is difficult to predict owing to strong dependencies on changes in atmo- spheric circulation, although there is growing confidence in projections of a general increase in high-latitude precipitation, especially in winter and an overall decrease in many parts of the tropics and sub-tropics (Anonymous, 2007b).
Precipitation is not the only influence on water availability.
Increasing evaporative demands owing to rising temperatures and longer growing seasons could increase crop irrigation requirements globally by between 5% and 20% or possibly more by the 2070s or 2080s, but with large regional variations, increasing in the Middle East and North Africa and South-East Asia (Doll, 2002; Abou-Hadid et al., 2003; Arnell et al., 2004;
Fischer et al., 2006) and decreasing in China (Tao et al., 2003).
The temperature increase due to elevated CO2 will also induce higher rates of evapotranspiration causing reduction in soil mois- ture (Schlesinger and Mitchell, 1985; Kellogg and Zhao, 1988;
Zhao and Kellogg, 1988; Parry et al., 1990). The areas which may suffer due to reduced soil moisture between December and February are southern and western Africa, South-East Asia, the Arabian peninsula, eastern Australia and southern North America, while between June and August are West Africa, western Europe, China, Soviet Central Asia, South-West United
States, Mexico, Central America, eastern Brazil and north-east- ern and western Australia (Parry et al., 1990).
Some major rivers such as the Indus and Ganges are fed by mountain glaciers with approximately one-sixth of the world’s population currently living in glacier-fed river basins (Stern, 2007). Populations are projected to rise significantly in major glacier-fed river basins such as the Indo-Gangetic plain. These river basins are irrigated agricultural land comprising less than one-fifth of all cropped area, but produce between 40% and 45% of the world’s food (Doll and Siebert, 2002). The major- ity of observed glaciers around the globe are shrinking (Zemp et al., 2008) due to changes in atmospheric moisture, particu- larly in the tropics (Bates et al., 2008). Melting glaciers will initially increase river-flow, although the seasonality of flow will be enhanced bringing with it an increased flood risk (Juen et al., 2007). In the long term, glacial retreat is expected to be enhanced further, leading to an eventual decline in run-off, although the greater time scale of this decline is uncertain. As such, changes in remote precipitation and the magnitude and seasonality of glacial melt waters could, therefore, potentially impact food production for many people.
Water for irrigation is largely often extracted from rivers such as the Nile and the Ganges, which depend upon distant climatic conditions (Gornall et al., 2010). Agriculture along the Nile in Egypt and in the Indo-Gangetic plains in India depends on rainfall from the upper reaches of the Nile and the Ganges in the Ethiopian Highlands and the Himalayas, respectively.
These areas are mostly between mid and high latitudes, where predictions for warming are the greatest. Warming in winter means that less precipitation falls as snow and that which accu- mulates melts earlier in the year. The changing patterns of snow cover fundamentally alter how such systems store and release water. Changes in the amount of precipitation affect the volume of run-off, particularly near the end of the winter at the onset of snow melt. Temperature changes mostly affect the timing of run-off with earlier peak flow in the spring. Although addi- tional river-flow can be considered beneficial to agriculture, this is only true if there is an ability to store run-off during times of excess to use later in the growing season.
Thus, climate changes remote from production areas is also critical. In rivers such as the Nile, climate change will increase flow throughout the year that will benefit agriculture, but in the Ganges, run-off increases in peak flow during monsoon season while in the dry season river-flow is very low. Without sufficient storage of peak season flow, water scarcity will affect