eChapters

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.

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.