eChapters

Introduction

Two types of interactions, i.e. competitive and complementary, are found in ecosystems and agroecosystems (Callaway 1998), which shape community structure, plant diversity and system’s functions (Callaway 1995; Pugnaire et al. 1996; Bruno et al. 2003). Competitive interaction in ecosystems (Wedin and Tilman 1993) and agro-ecosystems (Pandey et al. 1999) is well documented. Mechanism of complementary interaction, however, is not much understood so far. Some studies (Bertness and Callaway 1994; Callaway 1998) argue that complementary interaction is facilitative, either facultative or obligatory, and occur generally in harsh physical environments. This suggests that habitat amelioration by neighbours is a common denominator of positive interactions (Bertness and Callaway 1994; Callaway and Walker 1997). Other studies report that complementary interaction is mutualistic (Boucher et al. 1982). Irrespective of whether facultative or mutualistic, it is now well established that complementary interaction is evolutionary (Bertness and Callaway 1994). But, it is still inconclusive how two species exist together in ecosystems and agroecosystems (Bertness and Callaway 1994).

Introduction

Human civilization used to undergo several form of disasters throughout its life history. Most of such events are unpredictable, sudden and short in duration, and such events can easily classifiable as either natural (e.g. cyclones, earth quake, natural forest fires and tsunami) or manmade such as spread of toxic chemicals (e.g. Bhopal disaster 1984), nuclear explosions, civil war, diseases (Minamata, itaiitai, etc.). However, climate change is a real time prolonged disaster which is caused by both natural (caused by variation in solar irradiance, variations in orbital parameters of earth, volcanic activities, natural forest fire, methane release from thawing of permafrost from ocean floor, natural wetlands and cattle) and anthropogenic means (by greenhouse gases resulted from human activities-all kinds of combustion, industrial production of greenhouse gases and agricultural water lodging activities such as paddy cultivation and artificial wet lands, and deforestation).

Introduction

Throughout the arid zones, there is no dearth of problems, but rapidly increasing desertification (some call it land degradation) is a problem of worldwide dimension. Water is a scare commodity in arid zones. Much of rainfall is lost by evapo-transpiration and as a result, ground water recharged only by seepage through soil profile. However, it is a common phenomenon in arid zones of the world that ground water is frequently used at the rate that exceeds recharge. The situation in arid tropics of India, which is spread over an area of 31.7 million ha, is no more different. Considering the role of agriculture in the social and economic progress of developing countries, the vulnerability of agricultural systems to the impacts of climate change has received considerable attention from the scientific community (Fischer et al. 2002; IISD 2003; Kurukulasuriya and Rosenthal 2003). Much of the available literature suggests that the overall impacts of climate change on agriculture especially in the tropics will be highly negative, although in a few areas there may be minor increases in crop yields in the short term (Maddison et al. 2007). Research on agroforestry as an adaptation to climate change and as a buffer against climate variability is in the process of evolving.

Introduction

Rain fed agroecosystem occupies 68% of India’s cultivated area and supports 40% of the human beings and 65% of the livestock population. It produces 44% of food requirements, thus has and will continue to play a critical role in India’s agriculture (Singh et al. 2004). Besides their well established role in agriculture, livestock have crucial role in food security and as risk aversion mechanism for sustaining family, whenever there is crop failure. Indian hot arid zone which is about 12% of total geographical area of the landmass of 0.32 million km2 has maximum covering in western Rajasthan i.e. 61% of the total area whereas the other areas in arid region are available in the states of Gujarat, Punjab, Haryana, Andhra Pradesh and Karnataka accounting for 20, 5, 4, 7 and 3% of hot arid area whereas the cold arid area of 8.4 million ha lies in the state of Jammu & Kashmir covering the Leh and Ladakh region.

Introduction

A number of researchers have used morphological descriptors such as growth habit, leaf, shoot, flower, fruit morphology to classify and discriminate different varieties/cultivars and or detect inter and intra-specific variations in different tree species of economic importance (Saran et al. 2006; Holland et al. 2009). Such morphological descriptors are quite homogenous and often found insufficient to distinguish varieties within morphological groups. The choice of suitable cultivars is of paramount importance for its success. The lack of breakthrough has been due to under utilization of genetic variability for superior quality and high yield potential. Most of the fruit tree species demonstrates a rich genetic diversity mainly through natural cross pollination due to self incompatibility (Godara 1980). The elite plant types with desirable traits have been released as varieties, mass multiplied and propagated through standard vegetative multiplication. However, the authenticity of cultivar identification remains unclear (Devanshi et al. 2007).

Introduction

The area under salt-affected soils in India is estimated to be 6.73 Mha spread over a number of states across the country. This 6.73 million ha are lying barren or produce very uneconomical yields of crops due to excessive accumulation of salts. These soils are agriculturally unproductive because of the high content of soluble salts which had harmful effects on plant growth due to moisture stress and toxicity/deficiency of some of the ions and the exchangeable sodium ions in clay complex lead to the unfavorable physical conditions of for the plant growth and water movement (Bhumla 1977). Saline and sodic soils have excess concentration of either soluble or exchangeable sodium, calcium and magnesium primarily in the form of chlorides and sulphates. Salt affected areas an expected to increase with spread of waterlogging and salinity due to increase in canal irrigation, and intensive exploitation of poor quality ground waters for agriculture in non canal commands. Certain states like Rajasthan and Haryana located in the western part of the country are endowed with 84 and 62% of poor quality ground waters, respectively. Continuous use of such waters for irrigation to agricultural crops is bound to increase the problem of salinity and sodicity in India (Yadav 1989; Minhas and Bajwa 2001). Introduction of irrigation without making proper provision for drainage is the major cause for the development of salinity in canal commands.It is severe on irrigated lands of the dry zone. It reduces crop yield and in severe cases causes complete abandonment of agriculture (Joshi and Dhir 1989; Joshi et al. 2000; Mahesh Kumar et al. 2016). The present paper deals with extent, causes, characteristics and management options of these soils for sustainability of agriculture in the area.

Introduction

Desertification is affecting the livelihoods of millions of people, mainly poor in the dry lands, which occupy nearly 41% of the Earth’s land area and are the residence of more than 2 billion people of the world. In India, the western part of Rajasthan is mostly affected by desertification process dominated by wind erosion. Kar et al. (2009) reported that 15.2 mha land in western Rajasthan is affected by wind erosion out of total 22.96 mha area under desertification. A brief account on issues and priorities related to wind erosion processes in Thar desert was reported in Santra et al. (2006). Plenty of incident solar energy in the region makes the desert surface very hot especially during summer months. Wind speed also remains very high in the region for most of the time in a year. Therefore, the loss of top fertile soils through wind erosion process is very active in the region. Eroded dust particles during severe wind erosion events commonly known as dust storms not only create the soils poor but also pose several environmental threats through generating aerosols in atmosphere. 

Introduction

The world demand for wood is continuously increasing due to increase in population. The ever increasing population has led to depletion of existing timber reserves and the forestland base has been reduced by increased allocation of forest areas to urban, agricultural, recreational and other uses. The growing awareness towards development of plantations has generated a voluminous increase in the demand for quality planting material. Conventionally, propagation is achieved through sexual (seeds) or vegetative methods (rooting of cutting, grafting, layering, etc). Propagation through seeds is routinely used for production of planting material but it generates immense genetic variability which is not desirable while propagating perennial tree species. In order to propagate selected trees with desirable features vegetative propagation methods like rooting of cuttings, grafting, layering etc have been developed. These methods can produce genetically identical off springs thereby preserving the advantageous traits;

Introduction

Trees play an important role in ecosystem in all terrestrials and provide a range of products and services to rural and urban people (Gogoi 2015). As natural vegetation is cut for agriculture and other types of development, the benefits that trees provide are best sustained by integrating trees into agricultural system - a practice known as agroforestry. Agroforestry focuses on the wide range of trees grown on farms and other rural areas. Among these are fertilizer trees for land regeneration, soil health and food security; fruit trees for nutrition; fodder trees for livestock; timber and energy trees for shelter and fuel wood; medicinal trees to cure diseases and trees for minor products viz. gums, resins or latex products. Many of these trees are multipurpose, providing a range of benefits. Although effective and valuable tools have been introduced to evaluate the risk to construction in areas prone to geo-hydrological hazards, fewer steps have been made in the field of ordinary land use planning at different scales. 

Introduction

There is a growing interest in the role of different types of land use systems in stabilizing the atmospheric CO₂ concentration and reducing the CO₂ emissions or on increasing the carbon sink of forestry and agroforestry systems. Forestry has been recognized as a means to reduce CO₂ emissions as well as enhancing carbon sinks. There is considerable interest to increase the carbon storage capacity of terrestrial vegetation through land-use practices such as afforestation, reforestation, and natural regeneration of forests, silvicultural systems and agroforestry (Brown 1996; Canadell and Raupach 2008). Agroforestry systems are very important given the area currently under agriculture, the number of people who depend on land for their livelihoods, and the need for integrating food production with environmental services (Garrity 2004; Makundi and Sathaye 2004).

Introduction

Agroforestry is a land-use management system where trees or shrubs are grown around or among crops or in pasture lands. It combines agricultural and forestry technologies to create more diverse, productive, profitable, healthy, and sustainable land use systems.
India has been at the forefront of agroforestry research ever since organized research in this area started worldwide about 25 years ago. Considering the country’s unique land use, demographic, political and socio-cultural characteristics as well as its strong contributions to agricultural and forestry research, India’s experience in agroforestry research has proved important to agroforestry development especially in developing countries.

Introduction

The literatures and researcher data showed that there is negative impacts of agricultural expansion, landscape modification and deforestation on biodiversity, ecosystem services, alteringthe species composition and their ecological functions (Tscharntke et al. 2005; Priess et al. 2007; Flynn et al. 2009; Senior et al. 2013; Deguines et al. 2014; Kumar 2016) which can lead to considerable changes in critical ecosystem processes. On the other hand, an increasingly industrialized global economy, rapid population growth, land degradation, land use pattern and role of various human activities have led to dramatically increased the pressure on the natural resources such as the available land for sustaining the livelihoods, and with over exploitation and extraction of the natural resources the ecosystems are becoming unsustainable and fragile since last century (Kumar 2017). Standardization of cultural practices is one of the primary objectives to make the system ecologically, sustainable and economically viable (Gill et al.2009).

Introduction

Forest cover of India has been estimated to be 7,01,673 km2 (70.17 million ha) which is 21.34 per cent of the total geographical area of the country. The tree cover of the country is estimated to be 92,572 km2 which is 2.82 per cent of geographical area. The total forest and tree cover is 7,94,245 km2 which is 24.16 per cent of the total geographical area of the country. Out of this, 9.14per cent forest cover is in the form of open forests and another 1.26 per cent is scrub forests (FSI 2015). According to National Forest Policy 1988, one-third (33.33%) of the land area should be under the forest cover for sound ecological balance. It means that we have to bring another 11.66 % area under forest cover and at the same time improve quality of the degraded forests. However the horizontal expansion of land under tree cover is not possible. In order to increase the tree cover and fulfill the requirements of the people and industries,

Introduction

Homegardens are traditional agricultural systems, particularly common in the tropics characterized by a high plant diversity (Kumar and Nair 2004, 2006; Scales and Marsden 2008; Galluzzi et al. 2010), maintain high level of productivity, stability, sustainability and equitability (Soemarwoto and Conway 1992), serve as a refuge for wildlife (Perfecto and Vandermeer 2008), contributing significantly to the household diet by producing a large variety of food commodities (Kumar and Nair 2004; Wiersum 2006; Pulido et al. 2008; Kortright and Wakefield 2011; Kumar 2017; Kumar and Tripathi 2017), nutritional supplies (Mendez et al. 2001; Perrault and Coomes 2008; Vlkova et al. 2010; Balooni et al. 2014), supplementary cash income for owner (Huai et al. 2011; Arifin et al. 2012; Yang et al. 2014) and important spaces for transmission of cultural heritage (Galluzzi et al. 2010). Many native or endangered species can be found in homegardens (Albuquerque et al. 2005; Akinnifesi et al. 2010; Milow et al. 2013), and they are niches for domesticating semi-wild species (Akinnifesi et al. 2010). Plants grown, intentionally or unintentionally, in homegardens are important for household subsistence and economy.

Introduction

Agriculture expanded and forest dwindled. That eventually occurred with the expansion of civilization. Clearing of forests, granted in past, continued in modern times. Cutting of forests reached to such an alarming level that thinking of people turned back to create more forests. Sometimes over extraction of forest resources made forests unstable to yield perpetually according to necessity in future for which forests are turned unsupportive for livelihood and people tried for innovative means to enhance forest productivity in future (Nair 1993). Also with time agriculture faced the similar unfortunate condition towards intensive cultivation. So, peoples’ thinking turned back in agriculture how to make it stable and more supportive for livelihood year after year. Culturally human societies are connected both with agriculture and as well as forests from the time immemorial.

In contrast to the earlier and existing non-sustainable land use practices, agro forestry presents a more dynamic, productive and sustainable solution to the increasing demand of food, fodder, timber and other agricultural and tree goods. According to the United Nations,the world population was more than 7 billion in 2011 which is expected to go up to 9.3 billion by the mid-century. Consequently food production needs to be increased by over 60% by the year 2050. Agroforestry, which is a multifunctional, ecologically based, natural resource management system can help in dealing with such environmental, economic or social issues.

Key Facts
    
•    The United Nations Framework Convention on Climate Change (UNFCCC) defines ‘climate change’ as a ‘Change of climate 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 main green house gases (GHG) that have caused the global climate change or global warming are carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (NO₂).
    
•    CO₂ is the principal anthropogenic greenhouse gas that affects the Earths radiative balance. It is the reference gas against which other GHGs are measured and therefore has a Global Warming Potential (GWP) of 1. CH₄ and N₂O have a GWP of 21 and 310 respectively.
    
•    CO₂ is responsible for most of the enhanced green house effect of more than 50%, CH4 about 10 to 15% and NO2 about 4%.
    
•    The global atmospheric concentrations of carbon-dioxide, methane and nitrous oxide have increased since 1750, CO₂ increased from a pre-industrial value of 280 ppm to 379 ppm in 2005, CH₄ increased from 715 ppb to 1774 ppb and NO₂ increased from 270 ppb to 319 ppb in 2005.

Key facts

    
•    Though water is the most widely occurring substance on earth, freshwater accounts for only 2.5% whereas the rest of water is saltwater. The agriculture sector uses more than 75% of freshwater available. 
    
•    The current observed climate change impacts on water resources include increased precipitation at high latitudes and temperate areas, decreasing precipitation at low latitudes; decreasing snow covers, and glaciers in most regions; decreasing flows in some river basins; floods and droughts in some countries and significant decreases in lake and river size in Africa.
    
•    A number of climate models projected that a doubling of atmospheric concentrations of CO₂ would increase global precipitation by at least 5%.  The precipitation is expected to increase in some areas, such as, at high latitudes and in the tropics (south east monsoon regions and over the tropical Pacific), whereas the precipitation is likely to decrease in the sub-tropics (e.g. much of North Africa and northern Sahara).

Key facts

    
•    Agriculture is the major land use across the globe. Agriculture production (plant growth) is highly dependent on climate since crop growth is influenced by solar radiation, temperature and precipitation. Agriculture is also sensitive to climate variability and weather extremes (droughts, floods, severe storms).
    
•    The yields of C₃ crops (rice, wheat, and soybean) is expected to increase (10-20%) with predicted doubling of CO₂ concentrations compared to C₄ crops (maize, sorghum, millet, sugarcane) since C₃ plants respond readily/positively to increased CO₂ levels. Therefore, CO₂ enrichment may benefit temperate and humid tropical agriculture compared to semi-arid tropics.
    
•    The predicted rise of temperature could impact crop and horticulture yield if it exceeds optimal temperature range. For example, low latitudes crops are being grown near the limits of temperature tolerance and global warming may put them to higher stress.
    
•    On a world wide basis, global warming would benefit the mid to high latitude zones for agriculture (for a small change of temperature of 1-3^ºC), whereas low latitudes, semi-arid and tropical areas will have much reduced crop and livestock yields. However, adaptation measures may reduce such impacts.

Key facts

    
•    Fish is an important source of animal protein for billions of people (estimate 2.6 billion people). About 200 million people and their dependants worldwide, mostly in developing countries, live by fishing and aquaculture. 
    
•    Fish living in temperate and Polar Regions could be benefited from climate changes since an increase in water temperature would extend the fish growing season. Moreover, rising temperature could reduce over-wintering stress normally experienced by temperate fishes.
    
•    Rise of temperature may cause a decrease in dissolved oxygen (DO) or hypoxic conditions (as temperature and DO are inversely related) and can impair fish reproduction and may cause endocrine disruption in fish (increase incidence of malformations and may alter sex differentiation and sex determination in fish).
    
•    Bioavailability and toxicity of common pollutants such as pesticides and heavy metals may be enhanced with increasing temperatures. Therefore, exposure of toxicants at elevated temperatures may cause a decline in recreational and commercial fisheries.

Key facts

    
•    The climate change is likely to affect millions of people both directly (via increased deaths, disease and injury from heatwaves, floods, storms, fires and droughts) and indirectly (through changes in the water, air, food quality and quantity and ranges of vectors, such as mosquitoes, water-borne pathogens).
    
•    Recent observed climate change related effects include: (a) an increase in heat related deaths across the globe (Australia, Canada, France, Germany, the Netherlands, Portugal, Switzerland, UK and USA; (b) spread of vector- and rodent-borne diseases such as malaria (Africa, India) and dengue and (c) increase in food poisoning (New Zealand).
    
•    Heatwaves can cause adverse health effects such as heat cramps, fainting, heat exhaustion and heat stroke. Human deaths due to heatwaves are associated with cardiovascular and respiratory diseases and in 2003 in Europe 70,000 deaths were recorded from heatwaves alone.
    
•    Projections : (a) cold temperature is expected to become less frequent, while heat waves will become more frequent; (b) increases in heat related deaths and illness across the globe including Australia, Germany, Portugal, UK, and USA;  (c) malaria zone may expand in Australia, Africa (highlands), India and  260-320 million more people will be affected by malaria by 2080;  (d) dengue area is likely to increase as climate would be more suitable and by 2085, about 6 billion people will be at risk of contracting dengue fever including Australia and New Zealand; (e) diarrhoeal disease may increase with temperature increase; and (f) cholera outbreaks may rise as a result of more plankton blooms providing nutrients for Vibrio cholerae.

Key facts

    
•    The use of chemicals has many benefits, however, there are potential risks that some of these chemicals may cause harm to organisms and human health if they enter into the environment.
    
•    Harmful chemicals are those chemicals which are persistent, bio-accumulative, as well as toxic (PBT). 
    
•    Environmental or ecological risk assessment (ERA) consists of hazard identification, effect assessment, exposure assessment, risk characterization, risk classification, risk-benefit analysis, risk reduction and monitoring.
    
•    The five types of environmental monitoring are: chemical monitoring, bio-accumulation monitoring, biological effect monitoring, health monitoring and ecosystem monitoring. 
    
•    An integrated monitoring program is a coordinated monitoring activity comprising of both chemical and biological measurements in a variety of environmental compartments. There are four different monitoring levels in an integrated ERA, these are: suborganismals (biomarkers), organisms (bioassays), populations (bio-indicators) and ecosystems (ecological indicators).

Key facts

    
•    Arsenic (As) is a metalloid, with properties intermediate between those of a metal and a non-metal. Arsenic can exit in the environment and biological systems in various inorganic and organic forms (species). These are arsenite - AsIII, arsenate - AsV, monomethyl arsonic acid (MMAA), dimethyl arsinic acid (DMAA), arsenocholine, arsenobetaine and arsenosugars. 
    
•    Arsenicals have a wide range of toxicity. In general, inorganic arsenicals are more toxic than oragnoarsenicals to biota and trivalent arsenic (arsenite) is more acutely toxic than pentavalent (arsenate) form in the following orders:
    
    Arsenous acid (AsIII) ®  arsenic acid (AsV) ® MMAA ®DMAA ® arsenocholine ® arsenobetaine.
    
•    Under oxidizing and aerobic conditions, the predominant form of arsenic (As) in soil and water is arsenate (AsV), whereas under anaerobic and reducing/or waterlogged conditions, arsenite (AsIII) predominates.
    
•    Inorganic AsIII and AsV are the major As species in groundwater, soils, terrestrial plants, whereas the main species found in marine animals is Arsenobetaine (AsB), which is considered to be non-toxic.
    
•    The LD50 values of different arsenicals show that arsenite (AsIII) is most toxic (LD50 range 15-42 mg/kg) and arsenobetaine is least toxic (LD50 > 10,000 mg/kg).

Key Facts

    •    The heavy metals (HM) or trace metals in an aquatic environment can come from natural (e.g. geological minerals, wind blown silicate dust, volcanic emissions, sea spray and combustion) and anthropogenic sources (e.g. mining, industry and sewage treatment discharges as well as electronic waste and agriculture fertilisers). In aquatic systems, the heavy metals of greatest concerns are cadmium, copper, lead, mercury and zinc.
    •    Metals may exist in a number of physico-chemical states in aqueous systems such as particulate matter and dissolved forms. Metal speciation in freshwater is strongly influenced by hardness, alkalinity, pH, natural dissolved organic matter (DOM) and redox potential. 
    •    Water hardness is quantitatively related to metal toxicity in freshwater (i.e. toxicity of heavy metals decrease with increasing hardness and alkalinity; on the other hand, toxicity increases with decreasing salinity, dissolved organic matter and chelators). The uptake and toxicity of heavy metals of most metals in marine waters is low as compared to freshwater because metals are easily complexed with chloride ions.
    •    The toxicity of HMs is related to the dissolved ionic form of the metal rather than total concentration of the metal. Each different physico-chemical forms of an element has a different toxicity, for example, if the element (e.g. Cu) is absorbed on a colloidal particles it is expected to be of little or no effect on aquatic organisms, however,  if the copper is available as free Cu (II) ion, few aquatic organisms may survive.

Key facts
    
•    Pesticides are chemicals that are broadly used to protect crops, livestock and other animals and plants from pests and diseases. They are classified according to the type of pest to be controlled (algicides, herbicides, fungicides and insecticides).
    
•    Commercial production of DDT began in 1943. At that time, DDT was considered to be a wonderful invention. It was cheap to produce, very toxic to insects and much less toxic to mammals and its usage resulted in a sharp decline of mosquito borne diseases. In 1962, it was discovered that DDT was causing egg-shell thinning in bird eggs and thus was leading to the near extinction of bird species such as peregrine falcons and bald eagles.
    
•    Pesticides use has greatly helped to increase and improve the world food production. Use of pesticides also increases farmer’s profits by preventing crop losses due to pest attacks and weed infestation.

Key facts
    
•    Dioxins are the most dangerous and ‘super toxic’ chemicals so far known on the earth and three closely related families are collectively known as dioxins. These are Polychlorinated dibenzo-p-dioxin or dioxins (PCDDs), Polychlorinated dibenzofurans or furans (PCDFs) and polychlorinated biphenyls (PCBs).
    
•    2, 3, 7, 8-TCDD (or called TCDD) is the most potent of all the congeners. The toxicity equivalency factor or TEF of TCDD has been assigned as 1, while all other congeners assigned in order of toxicity ranking magnitude relative to TCDD.
    
•    There are 75 compounds/congeners in the dioxin family (PCDD), 135 compounds in the furan family (PCDF) and 209 possible compounds in the PCBs based on the possible number of chlorine atoms.
    
•    The toxicity of dioxins and dioxin-like compounds vary substantially among the different PCDDs, PCDFs and PCBs. It is generally accepted that only 29 out of the 419 congeners of dibenzo-p-dioxins, dibenzofurans and polychlorinated biphenyls are toxic to humans and other organisms. The TCDD is most toxic and registered by the WHO as carcinogenic for humans.

Key facts

    
•    Endocrine disrupting chemicals (EDCs) are micropollutants with estrogenic or androgenic activities at very low concentrations and are emerging as a major concern for water quality.
    
•    EDCs include natural and synthetic hormones (Estrone or E1, 17b-estradiol or E2, Estriol or E3, 17a-ethynylestradiol or EE2); alkylphenols (nonylphenol or NP; octyphenol or OP), phenols (bisphenol-A or BPA), phthalates (Di-n-butyl phthalate or DBP, Di-2-(ethylhexyl)-phthalate or DEHP); organotins (tributyltin or TBT); and phytoestrogens (b-sitosterol, coumestrols, genistein). 
    
•    Wastewater treatment plants, intensive livestock effluents, industrial wastewaters, landfill, paper and pulp mill effluents and antifouling paints are important sources of EDCs in the environment.

Key facts
    
•    Biotoxins are naturally occurring toxic compounds produced by some freshwater cyanobacteria (blue-green algae) and marine algal species (dinoflagellates, diatoms).
    
•    Tonnes of pharmacologically active substances are used annually in human and veterinary medicines, some of these substances are excreted (human and animal) non-metabolised or an active metabolites and enter into the environment since waste water treatment plant (WWTP) cannot degrade them.
    
•    In Europe, around 4,000 different pharmaceutically active compounds are used as human and veterinary drugs and the annual consumption is about several hundred tonnes.
    
•    European Union and the United States laws require an assessment of potential risks to the environment as part of license application processes for new medicinal products.

•    Pharmaceutical products are generally polar, water soluble and low volatile molecules, it means that they have high mobility in the environment.

Key facts

Freshwater biotoxins

    
•    Biotoxins are naturally occurring toxic compounds produced by some freshwater cyanobacteria (blue-green algae) and marine algal species (dinoflagellates, diatoms).
    
•    Cyanobacteria are now recognised as a serious water quality problem with regard to drinking water supply and recreational use.
    
•    Environmental conditions that can promote cyanobacterial/blue-green algal blooms are: excessive nutrients (phosphorus and nitrogen); warm water temperatures (15-30OC); sunlight for photosynthesis; and quiescent or stagnant water.
    
•    Outbreak of human poisoning attributed to cyanobacteria are neurotoxins (e.g. anatoxin-a, anatoxin-a(s), saxitoxins) and hepatotoxins (e.g. microcystins, nodularin) produced by some strains of the cyanobacteria including Microcystis, Anabaena, Aphanizomenon spp.

1.1 Introduction

Greenhouse effect, regulated by the presence of greenhouse gases in the earth’s atmosphere, is a natural process that plays a major part in shaping the earth’s climate. A continued rise in concentration of the greenhouse gases has led to enhanced greenhouse effect resulting in global warming and global climate change. The impact of human activities on greenhouse gases (GHGs) emission through fossil fuel burning, agriculture and industrial processes is important and familiar to people. This chapter addresses basic principles and physics of greenhouse effect and the role of Indian agriculture in GHG emissions. Agriculture is a potential source and sink to GHGs in atmosphere. It is a source for three primary GHGs: CO₂, N₂O and CH4 and sink for atmospheric CO₂ . Management of agricultural land, land use change and forestry has a profound influence on atmospheric GHGs concentration. The two broad anthropogenic sources of GHGs emission from agriculture are the energy use in agriculture (manufacture and use of agricultural inputs and farm machinery) and the management of agricultural land. Large sections of the India’s population depend on biomass resources like wood, crop residues and cattle dung for energy. In the agriculture sector, besides the CO₂ emissions due to burning of crop and animal waste, India’s large ruminant population and rice fields are significant contributors to CH₄ emissions. An understanding of GHG emissions by sources and removal by sinks in agriculture is important to take appropriate mitigation and adaptation strategies and to estimate and create inventory of GHGs.

2.1 Introduction

Weather has always been a popular topic but in the recent past it has received wide attention and debate as the public concern has increased about unforeseen changes in our climate. Over the 20^th century the average temperature of the earth has increased by 0.4 -0.8^oC. This increase is expected to continue and by 2100 the average global temperature is likely to be 1.4 - 5.8 ^oC warmer. One of the anticipated effects of climate change is the possible increase in both frequency and intensity of extreme weather events, such as heat waves, cold waves, hurricanes, floods and drought spells. The warming of the earth may fuel interactions between the ocean and atmosphere that will amplify the frequency and intensity extreme weather events. The possible changes in the frequency, distribution and intensity of extreme climate events have a significant influence at local, regional and global scales due to their multi-sectoral impacts on the overall economy.

3.1 Introduction

Ozone (O₃) is present throughout the atmosphere and can have either positive or negative effect depending on where it is found. The stratosphere (15-50 km) has the largest (90%) concentrations of O₃ (Colls, 1997). Stratospheric O₃ is important as it regulates the transmittance of ultraviolet light to the surface of the earth. Hence reductions in stratospheric O₃ in Polar regions, particularly the Antarctic “ozone hole”, are of concern regarding the health effects of exposure to increased levels of ultra violet (UV) radiation. In the troposphere (0-15 km), O₃ is a toxic pollutant of global importance and it is a major constituent of photochemical smog. Interest in pollutant O₃ and in its effects on living organisms has increased in the last decades as a consequence of the rise in its ground-level concentration and of the widening of its diffusion (Ashmore, 2005). Economic growth requires more energy production, which would result in increased production of NOx and volatile organic compounds (VOCs) precursors for O₃ formation (Ghude et al., 2008).

4.1 Introduction

Circumstantial evidences almost confirm researchers’ on early predictions of a changing climate and a warming world. The trend of changes also establishes the primary influence of increased greenhouse gas concentration on the global warming and the consequential events. The global mean surface air temperature has increased by about 0.74°C over the last 100 years. It is projected to rise 1.4 to 6.4 °C by the year 2100 (IPCC AR4, 2007). Changes will vary from region to region. Eleven of the twelve years in the period 1995-2006 rank among the top 12 warmest years in the instrumental record (since 1880). The radiative forcing of CO₂, CH₄ and N₂O is very likely (> 90% probability) increasing at a faster rate during the current era than any other time in the last 10,000 years. This is because of the increase in the global abundance of the three key greenhouse gases. The atmospheric CO₂ concentration has reached the level of 389 ppm in 2010 (WMO, 2011) from 270 ppm the pre-industrial era. In addition, global abundance of other greenhouse gases such as methane (CH₄) has increased from 700 ppb in the pre-industrial era to 1808 ppb in 2010 and in the same period, nitrous oxide (N₂O) has increased from 270 ppb to 323 ppb.

5.1 Introduction

In recent decades, human induced changes in climate of the earth have the focus of scientific and social attention. The most imminent of this is the increased concentration of greenhouse gases (GHGs) namely, carbon dioxide (CO₂), methane (CH₄) and nitrous oxide (N₂O) in the atmosphere. The concentration of CO₂, CH₄ and N₂O have increased markedly by 30%, 145% and 15%, respectively as a result of human activity since 1750, the era of Industrial Revolutions (IPCC, 2007). Between 1750 and 2005, the concentration of CO₂, CH₄ and N₂O in the atmosphere has increased from 280 to 379 ppm, 715 to 1774 ppb and from 270 to 319 ppb, respectively (IPCC, 2007). However, there was a steep increase during the recent years i.e. 70% increase of GHGs between 1970 and 2004.

6.1 Introduction

The change in climatic factors over the years is affecting the entire ecosystem. According to Intergovernmental Panel on Climate Change (2007), the global surface temperature is predicted to increase between 1.4 and 5.8 ^oC by the year 2100. Microbial and plant metabolic processes are often dependent on environmental factors (for e.g. temperature and moisture), enzyme activity, and nutrient availability all of which are likely to be affected by climate change (IPCC, 2007). The global atmospheric concentration of carbon dioxide, an important greenhouse gas (GHG) largely responsible for global warming, has increased from a pre-industrial value of about 280 ppm to 389 ppm at present. Similarly, the global atmospheric concentration of other important GHGs like methane and nitrous oxides has also increased considerably. The increase in GHGs was 70% between 1970 and 2004.

Rising atmospheric CO₂ is able to change the physiological activities of plants and soil micro organisms which in turn control the flow of carbon (C) and nitrogen (N) in terrestrial ecosystems. The change in climatic factors also alters the beneficial plant-microbe interactions, which may be positive, negative, neutral or having variable effects. The survival and activity of microorganisms in the rhizosphere mainly depend on the flow of carbon in the root exudates. The composition of these root exudates is affected by various environmental factors such as soil type, pH, light intensity, oxygen status, soil temperature, soil moisture and nutrient availability. Diverse microbial activities pose a major challenge to predict the response of microbial community to global climate change. These changes in microbial activity have larger impacts on vital ecological processes such as nutrient cycling.

7.1 Introduction

The current atmospheric CO₂ concentration is the highest during last 650,000 to 800,000 years (Luthi et al., 2008), and also probably in the last 20 million years (Pearson and Palmer, 2000). Since last two decades, it is increasing at a rate of about 2 ppm/yr with the current concentration of 389 ppm in 2010 (WMO, 2011). The current trend of energy use based on fossil fuel consumption may raise it to 900 - 1100 ppmby the end of 21^st century (Kiehl, 2011).

8.1 Introduction

Earth’s temperature has increased significantly due to the rise in concentration of greenhouse gases in its atmosphere. Naturally occurring greenhouse gases include water vapour (H₂O), carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O) and ozone (O₃). Prior to industrial revolution, the amount of greenhouse gases released into the atmosphere matched what could be absorbed by the natural sinks. Industrialization catapulted the addition of anthropogenically emitted gases to the environment, much beyond the natural levels. These greenhouse gases are building up, thus creating the effect of ‘global warming’. Global warming is a consequence of two major phenomena - depletion of the ozone layer and increase in greenhouse gas emission (Ishler, 2008).

9.1 Introduction

Background increase in anthropogenic emissions of Greenhouse gases, associated climate change and its global consequences are issues of concern. The Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (FAR) reveals that warming of the climate system is evident from the increase in global average air and ocean temperatures, widespread melting of ice and the rising global average sea level. The report states that the global mean temperature may increase between 1.4 and 5.8^oC by 2100, which will have severe impact on the global hydrological system, other ecosystems, the sea level, and agriculture. The impact could be particularly severe in tropical countries including India. Thus climate change is unavoidable and associated weather extremes such as high temperature and heat waves; increase frequency of droughts and high intensity rainfall causing flood are the issues of concern for Indian Agriculture.

10.1 Introduction

The IPCC predicts the global average surface temperature to increase by 1.4 – 5.8 ^oC by 2100 with the increased atmospheric carbon dioxide (CO₂) concentration from 540-970 ppm over the same period. The atmospheric CO₂ concentration and temperature, both, showing a steep rise since last three decades and their impacts experienced across all sectors of agriculture. Serious concerns have been raised about the effects of global environmental change on community and ecosystem functioning. Climate change scenarios generated from General Circulation Models (GCM) with a doubling of atmospheric CO₂ predicted various extreme weather events viz., warming temperatures, increase in anti-cyclonic behaviour during the summer which may result in 20% increase in the precipitation, and long periods of drought between rain bearing storms.

11.1 Introduction

Agriculture sector contributes 19% to the total greenhouse gas (GHG) emission in India. Combined with land use change and forestry (LUCF), it is the second largest source of GHG emission in India. Initial efforts at dealing with the problem of global warming concentrated on mitigation, with the aim of reducing and possibly stabilizing the GHG concentrations in the atmosphere (UNFCCC, 1992). Even if this stabilization was achieved, sea level rise and global warming would continue to increase over centuries because of the inertia of the earth systems. Mitigation activities are traditionally employed as natural resources conservation measures, but they generally serve the dual purposes of reducing the emission of GHG from anthropogen sources, and enhancing carbon ‘‘sink’’. Forestry sector holds the key to the success of mitigation efforts, and has great potential to sequester carbon through reduced emissions from deforestation and degradation (REDD), afforestation and reforestation, and forest management. India’s vast area of croplands, through cropland management, could be an important area for sequestering carbon in soils. India being the largest producer of rice and livestock in the world, appropriate management can contribute to a reduction of methane emission from rice production and enteric fermentation.

12.1 Introduction

The concentration of greenhouse gases (GHGs) in the atmosphere has been rising from historical levels, primarily due to fossil-fuel burning and land-use changes. These gases have the potential to trap energy from the sun, which may result in global warming, and this has sparked a world-wide concern that emissions of these gases should be reduced below the 1990 levels by the year 2012 (Kyoto Protocol). The international community has recognized the need to stabilize/reduce CO₂ and other GHG emission. The types of farm power, farm equipment and machinery have a significant influence on intensification and optimization outcomes, and on profit. However, until now, agricultural intensification generally had a negative effect on the quality of many of the essential resources such as soil, water, land, biodiversity and the ecosystem services which caused a decline in the yield and factor productivity growth rates. Another challenge to agriculture is its environmental food print and climate change. Agriculture is responsible for about 30% of the total greenhouse gas emissions, while being directly affected by the consequences of a changing climate. It is estimated that global conversion of all croplands to conservation tillage (CT) could sequester 5 billion tones of carbon annually.

In India significant efforts are underway to develop and popularize agricultural machinery and tools for resource conservation through the combined efforts of several State and National Institutions, particularly Rice-Wheat Consortium for Indo Gangetic Plains. The new technologies are encouraging the farmers to take up innovative ways of managing their resources for higher productivity and also providing a way to the scientific community to solve emerging problems of climate change. The farm machinery in conservation agriculture (CA) can reduce the emissions of fossil fuels compared to conventional agriculture by up to 60%. However, the largest contribution to mitigate climate change with CA can be obtained from carbon (C) sequestration and the storage of atmospheric carbon in the soil. The C -sink potential of soils varies depending on climate and production system. On an average 0.1-0.5 t. ha^-l y^-l of organic carbon can be sequestered under humid temperate conditions. Farm equipments like straw shavers and rotavators play a role in residue incorporation in the soil.

13.1 Introduction

Greenhouse gas (GHG) emissions have become an increasingly important topic worldwide due to their effects on global warming and climate change. The effects of GHG emissions on the ecological and socioeconomic vulnerability have already been noticed and will continue to grow regionally and globally in the years to come (IPCC 2007). Carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons, perflourocarbons, and sulfur hexafluoride are the important GHGs that are monitored by the United Nations Framework Convention on Climate Change (UNFCCC 2008). Global GHG emissions due to human activities (anthropogenic) have grown since the beginning of the industrial revolution with an increase of 70% between 1970 and 2004 (IPCC, 2007).

14.1 Introduction

Atmospheric concentration of CO₂ has increased from 280 ppm in pre-industrial era to 385 ppm in 2008 (+ 37.5%) and is presently increasing at the rate of 2 ppm yr^-1 or 3.5 Pg yr^-1 (1 Pg or petagram = 1 Gt = 1 gigaton = 1 billion metric ton). The increase in CO₂ emission by human activity is attributed to fossil fuel combustion, deforestation and biomass burning, soil cultivation and drainage of wetlands or peat soils. Increase in fossil fuel combustion is caused by high global energy demand of 475 Quads (1 quad = 1015 BTU) and increasing at the rate of 2.5 % yr^-1, especially in emerging economies including China, India, Mexico, Brazil, etc. The world population of 6.7 billion in 2008 is increasing at the rate of 1.3 % yr^-1 and is projected to be 9.5 billion by 2050 before stabilizing at 10 billion towards the end of the 21^st century. There exists a strong positive correlation between population growth on the one hand and CO₂ emission or the energy demand on the other. The People’s Republic of China accounted for 13% of the world’s C emissions in 2002 and that share is projected to rise to 18% by 2025 (Lal, 2004a).

15.1 Introduction

There is now adequate evidence about the impending global climate change and the consequences thereof. The fourth assessment report of IPCC observed that ‘warming of climate system is now unequivocal, as is now evident from observations of increase in global average air and ocean temperatures, widespread melting of snow and ice, and rising global sea level’ (IPCC, 2007). Though climate change is global in its occurrence and consequences, it is the developing countries like India that are likely to face more adverse consequences. Globally, climate change is seen as a failure of market mechanisms wherein the polluters haven’t had to pay for the negative externalities (Stern, 2007) that their economic activities caused.

16.1 Introduction

The ancient Greek philosopher ‘Heraclitus’ said, that, “You can’t step into the same river twice”. By this, he meant that permanence is an illusion and changes are inevitable. One of such changes, which has created buzz all over world is climate change. To understand the science behind climate change, the first step would be to know about the periodic changes in earth’s climate. Scientists devised innovative techniques to recover evidence from the distant past, first from deposits left on land, then from sea floor sediments, and one of the finest techniques of drilling deep into ice. Evidences from past climates help us to understand the evolution of the earth’s atmosphere, oceans, biosphere, and cryosphere. At the same time, paleo-climate studies help in quantification of properties of earth’s climate, including the forces that drive climate change and the sensitivity of the earth’s climate to those forces. When scientists investigate causes or complex processes in the present and future, they may find evidence in the past that helps them in mapping out the complexities (McMullen and Jabbour, 2009). The paleo-climatologists succeeded brilliantly and discovered strangely regular pattern of glacial cycles, which helps in prediction of future changes.

Introduction

Much of the world’s agricultural biodiversity is found in environments marginal for agricultural production. It is in such environments where management of high levels of diversity can become a central part of the livelihood management strategies of farmers and the survival of their communities. Abiotic stress can be termed as the negative impact of environmental factors on the organisms in a specific situation. It is a natural phenomenon that occurs in multiples and interdependent, and its impact varies across the sectors of agriculture. Abiotic stress is the primary cause of crop loss worldwide, reducing average yields for most major crop plants by more than 50%. Drought and salinity are becoming particularly widespread in many regions, and may cause serious salinization of more than 50% of all arable lands by the year 2050 (Wang  2003). Environmental stresses such as erratic and insufficient rainfall, extreme temperatures, salinity, alkalinity, aluminium toxicity, acidity, stoniness and others limit yield and productivity of many cultivated crop plants. Not only are such problems serious today, it seems they are inevitably worsening.

Introduction

Climate change is a big phenomena, it is having a huge impact on agriculture from ancient to present time. It has received wide attention and debate as the public concern has increased about unforeseen change in climate. The impact of climate change on Indian agriculture will be significant since more than 60% of Indian population depends on agriculture for their livelihood with the contribution of agriculture to GDP is approximately 20 percent. In recent decades, human induced changes in climate has the focus of scientific and social attention.

Introduction
 
Food production systems in India are becoming increasingly vulner-able to climate variability and change which are largely characterized by altered frequency timing and magnitude of precipitation and temperature that trigger a series of other devastating events. High rates of snow and glacial melting, frequent floods and droughts, heat waves, hail and increased incidence of pests and diseases are already causing widespread damage and losses to agricultural sector in tropical and sub-tropical countries including India. Overwhelming direct damage to crops and livestock within few minutes can be caused by extreme weather events such as hail, wind­storm, or heavy frost. While occurrence, losses and post disaster management have been discussed extensively for natural calamities such as excess rainfall, drought and flood, little attention has been given to hail storm.

Introduction

Increasing evidence over the past few decades indicate that significant changes in climate are taking place worldwide and its effects are surreal. Major cause to climate change has been ascribed to the increased levels of greenhouse gases like carbon dioxide (CO₂), methane (CH₄), nitrous oxides (N₂O), chlorofluorocarbons (CFCs) beyond their natural levels due to the uncontrolled human activities such as burning of fossil fuels, increased use of refrigerants, and enhanced agricultural activities. Global average sea level has risen since 1961 at an average rate of 1.8 (1.3 to 2.3) mm/yr and since 1993 at 3.1 (2.4 to 3.8) mm/yr, with contributions from thermal expansion, melting glaciers and ice caps, and polar ice sheets. The climatic changes are resulting in erratic weather patterns and the impacts are already being manifested in many parts of the world and coastal agricultural systems are nearing crisis point. The IPCC has projected that during the 21st century the global surface temperature is likely to rise a further by 1.1 to 2.9 °C as per their lowest estimation model and by 2.4 to 6.4 °C as per their higher estimation model.

Introduction

Agriculture plays a crucial role in ensuring food security, accounting for a significant share of India’s Gross Domestic Product (GDP). Agriculture is not just about food production alone, since it is a complex multi-dimensional and multi-faceted sector which concerns the efficient use of the natural resources, productivity enhancement, and preservation of the ecosystems in a manner that can sustain the needs and improvements of human livelihoods (Devendra, 2012). It is also a most vulnerable sector to climate change which has been recognized as one of the most serious challenge for the world- its people, the environment and its economies. Increased incidence of abiotic stresses (drought, high & low temperature, salinity, submergence and oxidative stress) and biotic stresses (pest and diseases) have became major cause for stagnation of productivity in major crops (Grover et al., 2011). Abiotic stresses are directly correlated with the change in climate while biotic stresses are indirectly correlated as the pattern and incidence of disease varies with the variation in climatic condition. Also, crop productivity rely on extent and type of stress in the particular area.