eChapters

General Introduction 
Growing populations and industrialisation around the world are driving up energy demand, which increases reliance on fossil fuels. The World Energy Forum projects that global stocks of fossil fuels like coal, natural gas, and oil will run out in less than ten years and decades [1]. Fossil fuels account for 88.1% of total energy consumption; they include coal (43%), oil and other liquids (23%), waste (6%), natural gas (6%), and biomass (24%). Hydroelectricity, and nuclear energy, on the other hand, share relatively small percentages of energy (1% and 2%, respectively) [2]. Petro-diesel, also known as petroleum diesel, is currently utilized as a fossil fuel and is created when crude oil is fractionally distilled at temperatures between 250°C and 350°C under atmospheric pressure. Once heated to a certain degree, the different types of diesel fuel are formed via the vaporization of hydrocarbon chains and the isolation and blending of constituents in a prescribed ratio. Typically, 25% of the petrodiesel’s composition consists of aromatic hydrocarbons and 75% of saturated hydrocarbons. The combustion of diesel fuel releases sulfur, nitrogen, and particulate matter into the environment, which are all present in significant concentrations in petro-diesel. Moreover, burning fossil fuels has resulted in several environmental problems, such as greenhouse gas emissions (GHG), which have a major impact on global warming, climate change, and a host of other chronic illnesses [3]. India is ranked as the fourth-biggest importer and user of petroleum products and crude oil. With demand for oil reaching about 4.1 million gallons per day in 2015, there is a growing disparity between India’s oil supplies and supply. The IEA analysis predicts that beyond 2050, there won’t be any oil reserves and that India’s oil consumption will increase by 6.0 million barrels per day to 9.8 mg/d in 2040 [4]. Two-thirds of the growth in oil demand and 16% of the increase in

Introduction The idea of LiFE was introduced by the Prime Minister during the 26th United Nations Climate Change Conference of the Parties (COP26) in Glasgow from 31st October to 13 November 2022. The idea promotes an environmentally conscious lifestyle that focuses on ‘mindful and deliberate utilisation’ instead of ‘mindless and wasteful consumption’.(PIB India)

The LiFE Movement aims to utilise the power of collective action and nudge individuals across the world to undertake simple climate-friendly actions in their daily lives. The LiFE movement, additionally, also seeks to leverage the strength of social networks to influence social norms surrounding climate. The Mission plans to create and nurture a global network of individuals, namely ‘Pro-Planet People’ (P3), who will have a shared commitment to adopt and promote environmentally friendly lifestyles. Through the P3 community, the Mission seeks to create an ecosystem that will reinforce and enable environmentally friendly behaviours to be self-sustainable.

Introduction 
A major challenge facing the world today is making the transition to a sustainable and resource-efficient economy, especially considering climate change, resource depletion, and rising waste production. The idea of a circular economy has drawn a lot of attention in this setting. In contrast to the conventional linear economic paradigm of “take-make-dispose,” the circular economy prioritizes closed-loop solutions that reduce waste and environmental impact by reusing, recycling, and regenerating resources. The efficient use of biomass as a plentiful and renewable resource to produce biofuels, biochemicals, and bio-based products is a crucial part of this circular framework. The combination of cellulose, hemicellulose, and lignin, known as lignocellulosic biomass, is one of the most widely available and sustainable types of feedstocks for biomass. Originating from forestry byproducts, specific energy crops, and agricultural residues like corn stover and wheat straw, lignocellulosic biomass is a feasible substitute for raw materials derived from fossil fuels [1]. By minimizing reliance on non-renewable resources and supporting sustainable waste management, its conversion through biorefineries into a wide range of bio-based goods is fully in line with the concepts of the circular economy [2]. Integrated systems known as lignocellulosic biorefineries maximize resource efficiency and reduce environmental impact by converting all the components of biomass into marketable products. The production of biofuels (such as bioethanol and biodiesel), platform chemicals, bioplastics, and energy by these biorefineries greatly aids in the creation of renewable energy and sustainable industrial processes [3]. Biorefineries can maximize the utilization of biomass feedstocks by converting them into high-value products while upholding zero-waste principles by utilizing a variety of biochemical and thermochemical conversion processes [4]. A summation of the function of lignocellulosic biorefineries in promoting the circular economy is given in this chapter. The first section covers the current developments in pretreatment and conversion methods as well as the composition of lignocellulosic biomass. By incorporating these technologies into biorefinery systems, waste valorization and energy efficiency issues can be resolved, and biobased goods can be produced more effectively. This chapter also examines the prospects and problems faced by lignocellulosic biorefineries, looking at their technological, economic, and regulatory elements as well as how they might help with the worldwide transition to a circular bioeconomy.

1. Introduction
Increasing population, industrialization, and change in the human lifestyle have become the reason for the exhaustion of non-renewable energy sources, our prime energy resource. The combustion of non-renewable energy sources produces toxic pollutants such as CO2, CO, NOx, SO2, etc., and greenhouse gases CH4, CO2, and N2O which significantly contribute to global warming, environmental pollution, and health hazards. In the current scenario, we need a green energy source that does not generate toxic gases and is eco-friendly. Hence, the research is triggered towards finding alternative solutions to overcome the energy crisis. The various green energy sources are solar, wind, tidal, geothermal, hydropower, biomass, hydrogen fuel cells, etc. The major drawback of these sources is the geographical location to install the plants. In the present context, identifying an alternate energy source that is sustainable, renewable, and eco-friendly to overcome the ever-growing energy demands is crucial. Hence, bioenergy is an eco-friendly, economical, and sustainable source of energy that gratifies the contemporary development environment by utilizing the potential of renewable organic energy resources (Yin and Wang et al., 2022).
2. Biomass
The sources of biomass are agro wastes, wood wastes, aquatic wastes, municipal wastes, wet wastes, industrial wastes, forest residues, etc. Figure 1.1 illustrates various sources of biomass, such as agricultural leftovers, forestry waste, energy crops, and organic municipal waste, showcasing their potential as renewable energy resources. Biomass is the product of photosynthesis and is also a versatile renewable energy source that can be utilized for sustainable biohydrogen generation. Biomass absorbs atmospheric CO2 during its growth, leading to relatively a lower net carbon impact as compared to fossil fuels. Renewable organic resources (biomass) can be in a solid, liquid, or gaseous phase. Energy generation through the incineration of biomass has been a longstanding practice. Since the energy potential of the biomass is not extracted effectively, it leads to environmental pollution (Kumar and Fiori et al., 2024). Biomass can be converted to liquid and gaseous fuels called biofuels with significant calorific value through thermochemical and biochemical processes (Gautam et al., 2020). Biofuels are superior to fossil fuels in the context of sustainability and reduced emissions of greenhouse gases. A variety of biofuels and chemicals such as bio-ethanol, biodiesel, acetic acid, formaldehyde, etc., can be manufactured from biomass (Gautam et al., 2020). Globally, research is advancing towards replacing non-renewable fuels with biofuels. However, the transition to biofuel technique presents a challenge due to the huge space requirement for biomass. Table 1.1 illustrates the categories of biomass employed for hydrogen generation, categorized into lignocellulosic materials, algal biomass, organic waste, and energy crops.

Despite the meticulous methodology and extensive analysis employed throughout this research project, it is crucial to acknowledge and address the limitations that arose during the study. By recognizing these limitations, we not only ensure a transparent evaluation of the research process but also shed light on potential areas for future investigations to refine and expand upon the findings.

In this section of the chapter, the limitations encountered in this thesis are highlighted as follows:

1. Due to the complexity of the concept, obtaining quantitative responses proved to be exceedingly challenging.

2. The development of improved scales for scoring could have enhanced the research if implemented.

3. The inclusion of a greater number of relevant variables could have provided a more comprehensive and in-depth understanding of the research topic.

4. Deploying mathematical optimization and simulations could have effectively integrated and co-integrated the seemingly disparate aspects of climate change perception, uncertainty perception, and perception of agricultural dynamics.

5. Presently, farmers are hesitant to engage in conversations and provide data to individuals outside their close social circles.

ABSTRACT

Lineaments are the surficial expression of sub-surface phenomena which are well discerned from low-orbital data, satellite data with its synoptic view and repetitive coverage and help to bring out more information on structural features hither to unknown by conventional geological surveys. Their study paved way to many new concepts on tectonism, mineralization, structural deformity etc. of an area both in regional and local perspective. In the present study, a small area was selected after careful observation, for their importance in mineral deposits. The lineaments are mostly structurally controlled and analysed for their relationship with the base metal deposits of the area. Moreover satellite parameters like spatial resolution, scale etc., and are observed for their changes in their orientation and relationship with the deposit of the study area, Jambughoda of Panchmahal District, Gujarat Satellite data of Landsat MSS and TM are used for the analysis. The results proved that the satellite parameters are important criteria and play a vital role in lineament analysis for mineral investigation.

Abstract

The frequently recurring earth tremors / Seismicities in parts of Tamil Nadu & Kerala and the earthquakes of higher magnitude in Central India in the recent years have gradually dissolved the concept of shield area stability for the South India and the concept of mid-plate seismicity has emerged in the minds of geoscientists, Hence, the geoscientists have embarked into a number of studies to bringout seismotectonic maps for South India. In this context, a detailed studies have been carried out by the authors in parts of westernghats (Kodaikkanal and Varushanad hills) in Tamil Nadu. In the said study lineaments were interpreted using high resolution IRS satellite data and from the lineament pattern, isofracture, lineament density and lineament interaction intensity the strain maxima axes were drawn. Such strain maximas were observed to fall in N- S, E – W and NE –SW directions. These strain maximas were found to coincide with various drainage anomalies, like radial, compressed meandering and eyed drainages indicating that these lineaments are prone for seismicity/ earth tremors.

9.1 Introduction

Biomass conversion is a transformative process that harnesses the energy and chemical potential of organic materials derived from living organisms. It encompasses various methods of converting biomass, including agricultural residues, forestry by-products, algae, and even waste materials, into valuable products such as biofuels, chemicals, and energy. This process is a cornerstone of sustainable resource utilization and plays a critical role in addressing environmental concerns, reducing reliance on fossil fuels, and promoting a circular economy. Biomass conversion methods range from biochemical processes like fermentation and anaerobic digestion to thermochemical processes such as combustion, pyrolysis, gasification, and liquefaction. Each method employs distinct conditions, catalysts, and technologies to break down complex biomass structures and convert them into desired products.

16.1 Introduction

Littoral drift is a geological process by which sediments such as sand or other materials, move along a beach shore.Long Shore Drift is the movement of eroded material, in a zig zag way, along the coast. The process arises when waves approach the shore obliquely. That is to say, at an angle other than 90°. The effect of this is determined by factors such as the direction and fetch of the present wind and, in the long term, of the prevailing wind.

Waves striking the shore at an angle as opposed to straight on will cause the wave swash to move up the beach at an angle. The swash moves the sediment particles up the beach at this angle, while the backwash brings them, solely under the influence of gravity, directly down the beach. Some geologists consider a beach to be merely a shoreline feature of deposited material, but William Bascom (1980) has argued that a beach is the entire system of sand set in motion by waves to a depth of ten meters or more off ocean coasts. Submerged, longshore bars are therefore also part of the beach, and thus beaches can be viewed as either:

Livestock population meet the protein requirement of humans in addition to meeting from plants. The food chain starts from fodder crops to animals and from animals to humans. In human physiology, digestion of plant protein is much easier than animal protein, but however the digestion depends on climate (temperate climate, sub-tropical climate, tropical climate etc.,) wherein human kind live. Similar to crops, there is strong interaction between livestock and meteorological weather elements (temperature, relative humidity, wind etc.). But detailed study has not been published elaborately in scientific journals in the past. The weather elements have greater influence on livestock productivity in terms of milk, meat, skin, wool etc., pest and disease infestation and their housing needs. In this chapter how weather elements influence shed management, pest and disease problem and animals’ productivity and are discussed. In majority of the Veterinary and Animal Science University in India, they have one division on animal climatology, wherein both research and extension aspects are being attended. However, in depth research is the need of the present decade, since little works have been done in the past on animal climatology.

Irrespective of weather elements, the heat stress due to the combination of temperature and relative humidity plays important role in affecting the productivity of animals. There is a range of thermal conditions within which animals are able to maintain a relatively stable body temperature by means of behavioral and physiological means. Heat stress results from the animal’s inability to dissipate sufficient heat to maintain homeothermy (Sejian et al., 2017). High ambient temperature, relative humidity and radiant energy compromise the ability of the animals to dissipate heat. As a result, there is an increase in body temperature, which in turn initiates compensatory and adaptive mechanisms to re-establish homeothermy and homeostasis. Homeostasis refers to the tendency to maintain a balanced or constant internal state that is optimal for functioning. Animals have a specific balanced or normal body temperature. When there is a problem with the internal functioning of animal body, this temperature may increase, signaling imbalance. As a result, body attempts to solve the problem and restore homeostasis for normal body temperature. These readjustments generally referred as adaptations and this is essential for survival of the animals.

As we look to the future, climate crisis is looming large and it is essential to address several aspects of climate-resilient agriculture. One of the critical areas that require attention is scaling up climate-resilient agricultural practices. This involves promoting and supporting the adoption of climate-resilient agricultural practices, such as conservation agriculture, agroforestry, and climate-smart agriculture, among small-scale farmers and rural communities. There is vast scope for upgrading traditional technologies making best use of modern technologies. To achieve this, there is a need:
• To increase funding and investment in climate-resilient agriculture. This can be achieved through a combination of government funding, private sector investment, and international aid. The funding should be used to support research and development, technology transfer, and capacity building, as well as to provide financial incentives to farmers to adopt climate-resilient agricultural practices.
• Strengthening international cooperation is also critical for promoting climate-resilient agriculture. This involves sharing knowledge, expertise, and resources among countries, as well as collaborating on research and development, technology transfer, and capacity building. International cooperation can also help to promote policy and institutional reforms that support climate-resilient agriculture.
• Promoting climate information and early warning systems. This involves providing farmers and rural communities with accurate and reliable climate information, as well as early warning systems that can help them prepare for and respond to climate-related disasters. Climate information and early warning systems can be provided through a range of channels, including mobile phones, radio, and television.
• Supporting climate-resilient agricultural research and development is also critical for promoting climate-resilient agriculture. This involves investing in research and development that focuses on improving crop varieties and animal breeds, developing new technologies and practices, and improving our understanding of the impacts of climate change on agriculture. Research and development can also help to identify and promote climate-resilient agricultural practices that are suitable for different regions and contexts.
• Promoting policy and institutional reforms is also essential for supporting climate-resilient agriculture. This involves promoting policies and

Farmers’ data collection can be a valuable input for the development of agrometeorological advisories because it provides a unique perspective on the local weather and climate conditions that affect their crops and farming practices. Farmers have a deep understanding of the local environment and are often able to observe subtle changes in weather patterns and soil conditions that may not be captured by traditional meteorological instruments. By collecting data on weather patterns, soil moisture, crop growth, and other factors, farmers can provide valuable insights into the complex relationships between weather, climate, and agriculture. This data can be used to improve the accuracy and relevance of agrometeorological advisories, which are critical for helping farmers make informed decisions about planting, irrigation, pest management, and other aspects of crop management. By incorporating farmers’ data into the development of these advisories, researchers and policymakers can create more effective and targeted recommendations that take into account the specific needs and conditions of local farming communities. Furthermore, the collection of farmers’ data can also help to identify gaps in existing meteorological data and provide insights into the impacts of climate change on local agriculture. This information can be used to inform the development of more effective climate adaptation strategies and to support the creation of more resilient and sustainable agricultural systems.
In addition, the involvement of farmers in data collection can also help to build trust and promote the adoption of agrometeorological advisories. By working closely with farmers and incorporating their knowledge and expertise into the development of these advisories, researchers and policymakers can create more effective and sustainable solutions that meet the needs of local farming communities. Overall, the collection of farmers’ data can provide a valuable input for the development of agrometeorological advisories, helping to create more effective, targeted, and sustainable solutions that support the needs of local farming.
5.1 Low Cost Instrumentation
The use of low-cost instrumentation in agriculture is essential for enabling farmers to collect accurate and reliable data on various parameters that affect crop growth, soil health, and farm management. In many developing countries, smallholder farmers lack access to expensive and sophisticated equipment, making it difficult for them to make informed decisions about their farming practices

Algae are organisms that grow in an aquatic environment and use light and carbon dioxide (CO2) to produce biomass. There are two categories of algae: macroalgae and microalgae. Macroalgae, measured in inches, are large multicellular algae that often grow in ponds. Macroalgae refers to thousands of macroscopic and multicellular seaweed species. The term includes some species of macroalgae such as Rhodophyta (red), Phaeophyta (brown), and Chlorophyta (green). Algae species such as kelp provide important breeding habitats for fisheries and other marine species, thereby protecting food sources; Other species such as plankton algae play an essential role in carbon sequestration and produce up to 90% of the Earth’s oxygen. Macroalgae, or large seaweeds, grow very rapidly and can reach extraordinary lengths up to 60 meters (McHugh, 2003). Their growth rates are much higher compared to many land plants. For example, wild brown algae can yield between 3.3 and 11.3 kg of dry biomass per square meter each year, and cultivated varieties can produce up to 13.1 kg in just seven months. In contrast, sugarcane, which is known for its high productivity, typically produces 6.1 to 9.5 kg of fresh biomass per square meter per year (Kraan. 2010). Additionally, macroalgae are available naturally in water bodies on a seasonal basis, and farming them in the ocean does not require traditional farming land or fertilizers. This makes them a promising option for addressing energy needs, as they are not only used for food and hydrocolloid extraction but also have potential for ethanol production. Humans have a long history of growing algae for uses such as food, food additives, feed, textiles and papers, bio-plastics. In recent years, seaweed farming has become a worldwide agricultural practice, providing food and feedstock for various chemical uses such as carrageenan, animal feed, biofertilizers and growth promoters. Due to its importance in marine ecology and carbon uptake, recent attention has focused on kelp farming as a potential climate change mitigation strategy for carbon dioxide biocapture, along with other benefits, such as reduced nutrient loads and increased habitat for coastal aquatic species, and reduced local ocean acidification in addition to biofuel opportunities. The seven most commonly cultivated algal taxa are Eucheuma spp., Kappaphycus alvarezii, Gracilaria spp., Saccharina japonica, Undaria pinnatifida, Pyropia spp. and Sargassum fusiform. Eucheuma and K. alvarezii are cultivated for carrageenan (a gelling agent); Gracilaria is grown for agar; while the rest is grown for food. Macroalgae production has become a cornerstone of global aquaculture, serving diverse industries such as food, biofuels, and pharmaceuticals

12.1 Introduction

A magneto hydrodynamic energy conversion system or MHD system converts heat energy directly into electricity. An MHD generator produces electricity via the interaction of a moving fluid with a magnetic field and ionized gas. MHD conversion does not involve any mechanical conversion intermediary. As a result, this process offers substantial fuel savings because the process of producing mechanical energy and then converting it to electrical energy is eliminated. It is possible to generate electricity in large quantities using MHD power plants while reducing the impact on the environment. During his Bakerian lecture in 1832 to the Royal Society, Michael Faraday presented the concept of MHD power generation for the very first time. 

Introduction 
Maize (Zea mays L.) which belongs to the Poaceae family, has its roots in the American continent where it was once grown by ancient cultures like the Indians, Magyars, and Aztecs. Today, maize is one of the most widely cultivated crops globally, with the largest productions in countries such as the US, China, India, and Brazil. As a monocotyledonous and cross-pollinated annual plant, maize is an angiosperm with seeds enclosed in a fruit or shell. The root system of maize is fibrous, reaching up to 60 cm. in soil depth. Maize is a warm-season crop with specific agro climatic requirements for successful cultivation. It thrives in warm temperatures and requires a minimum temperature of around 10°C (50°F) for germination. The ideal temperature range for its growth is between 20°C and 30°C (68°F to 86°F). However, maize is sensitive to frost, and exposure to freezing temperatures can damage or kill the crop. Adequate and well-distributed rainfall is crucial during its growing season, as maize needs about 500 to 1000 mm. (20 to 40 inches) of rainfall to support its development, with higher water requirements during flowering and grain-filling stages. While the crop is moderately droughttolerant, moisture stress at critical growth stages can significantly impact yield. Maize is a sun-loving crop and requires long daylight hours with ample sunshine for efficient photosynthesis and plant growth. The soil should be well-drained, loamy or sandy, rich in organic matter, and have a pH ranging from 5.8 to 7.0 (Greaves et al., 1996). Avoiding waterlogged or compacted soils is crucial, as they can impede root development and nutrient uptake. Maize can be cultivated at varying altitudes, but its suitability is generally limited to elevations below 2,500 meters (8,200 feet) above sea level. The crop typically requires 90 to 120 days from planting to maturity, although some varieties with shorter growing seasons are available for regions with limited frost-free periods. High salinity can result in decreased plant leaves, green weight, fresh weight, shorter shoots, and root length but salt-tolerant varieties have been developed.

Among subtropical fruit crops mango, guava, bael and aonla are among the most important ones. The productivity of these crops is affected by many factors, among which diseases have their own economic significance. The crops use to suffer from a large number of diseases, however, economically important diseases having significance in agro-advisory are mentioned below.
Mango Wilt and Decline
The mango wilt disease caused by Ceratocystis fimbriata is one of the most devastating diseases (Shukla et al., 2015, 2018b, 2020; Shukla, 2020). Association of Berkeleomyces basicola and Lasidiplodia theobromae in wilt, decline and branch drying has also been observed. Symptoms: Ceratocystis infection on the trees causes dark staining of the affected wood, exudation of gum, leaf drying and ultimately death of the tree (Al Adawi et al., 2003; Shukla et al., 2018b). Later symptoms include vascular discolouration beneath the gummosis (Masood et al., 2008; Shukla et al., 2018b). The symptoms may appear in the form of sudden wilt, decline or branch drying and accordingly the whole tree or branch may die within a period of a fortnight to six months of appearance of first symptom.

Introduction

 India, situated between the latitude of 08004’ and 37006’ N and longitudes of

68007’ to 97025’ E, has a geographical area of 329 Mha. Physiographically, it

can be divided into three broad regions, viz., Peninsula (a triangular Plateau in

the Deccan and South of the Vindhyas), Mountain region of the Himalalayas

(Extra-Penninsula), and the Indo-Gangetic Plain separating these two regions.

Geologically, a great part of the Penninsula is occupied by the gneiss, schists

and other rocks of diverse nature. Red soils (Alfisols) generally predominate in

this region. The western and central parts predominate in basaltic rock having

Black cotton soils of different thickness (Vertisols, Inceptisols). The mountain

region shows the development of marine sediments of all ages, especially, in

north of the Himalayas. The vast Indo-Gangetic and other plains of Pleistocene

origin are composed of alluvium of the great river systems flowing in this

region. The alluvial soils of this region depend on the age of alluvia and degree

of development.

Climatically, India shows three distinct seasons:

 i) Cool and mainly dry winters from November to February

ii) Hot and mainly dry summers from March to June

iii) Monsoon rainy season from mid-June to September.

Abstract

The landslides that swallowed the whole of Malin village, Maharashtra on the early morning hours of 30 July, 2014 is one of the major disasters, next only to Kedarnath episode in the recent years. Consequently, the Department of Science and Technology, New Delhi, constituted an expert committee comprising the authors of the article which made a visit and took the on the spot assessment of the disaster. Their observations show that the area is covered by the Deccan basalts, which are layered with compact and vesicular basalts; fractured and jointed basalts due to tectonics and the cooling of the basalts; and have also undergone extensive geomorphic evolution. Due to such geologic/geomorphic setting, the flow layered basaltic hillock in which Malin is located is naturally benched, which is further being leveled for the agriculture purposes. The deforestation, leveling of the hills, excessive usage of water for irrigation and the lack of drainages outlet in such benched and leveled slopes have assigned high degree of landslide vulnerability to the area. Over this, when torrential rainfall occurred in the last week of July, the landslide was triggered. On the basis such inferences, some mitigation measures have been evolved after the visit.

In his classic book ‘The Ascent of Man’, Bronowski has written, “When I was a young man, we all thought that mastery came from man’s domination of his physical environment. Now we have learned that real mastery comes from understanding and moulding the living environment.” Our Biosphere, the living environment that supports us all, has problems and we humans are mainly responsible. We do not live ‘gently’ on the earth. The seven billion of us require air, water, food, energy, housing and amenities and we have developed the earth to provide them and have also created problems. That the problems exist are serious is the bad news. That we are recognizing them and that man has shown ability to organize and grow in ascending order from time to time is the good news.

1.1 The relation between man and the earth’s resources

The balance between the demand which a community of plants or animals makes on its environment and the ability to satisfy those demands is not the static equilibrium of a laboratory balance with equal weights on either side. It is more like the unstable balancing of a circus acrobat - a series of swings and overcorrections, resulting in an oscillation on either side of the true balance point. Thus a species of wild life increases in number according to the availability of its food supplies, but then goes beyond the optimum number. The natural correcting factors of starvation or migration reduce the population, but there is an overcorrection, and soon the cycle starts again with increasing numbers.

1.1.1 The Malthusian Thesis

In primitive societies the human population also oscillates about a mean as the limiting factors of starvation, disease, and war, maintain an uneasy balance against the natural tendency to increase. A serious imbalance arises when man learns how to modify the limiting factors, but allows the natural increase to go unchecked. The essence of the Malthusian Thesis is that the resulting instability is the inevitable order for mankind. The thesis is named after the English political economist Thomas Malthus who first gave it formal expression in MALTHUS (1966). In an age when significant improvements in health, hygiene, and the standard of living were just becoming possible, Malthus aroused great argument when he pointed out that these very improvements could lead to mi sery through overpopulation. The key point of Malthus’s argument is that population increases in what he called geometric ratio, what today we would call an exponential curve, because whenever there is an increase in population there are more people to produce the next generation, so the rate of population growth accelerates - in modelling terms a positive feedback loop. On the other hand, when we increase food production there is no feed-back loop, the best we can hope for is for a constant linear increase. The natural sequence is therefore for food demand to increase faster than food supply, leading at some point to food shortage.