Sustainability & Environment (Agri-Food Systems) · Foundations · also Environmental Studies, Environmental Studies & Disaster Management (ICAR UG), Introduction to Environmental Science, Ciências do Ambiente
The map of the whole field: the four spheres, natural resources and their status, human population and consumption, and the main environmental problems an agricultural graduate meets. Compulsory in most undergraduate degrees worldwide and the opening unit of ICAR AICE subject 71.
In the exams: ICAR AICE-JRF/SRF subject 71 Unit 1; ICAR AIEEA-PG 3.6; UGC NET Environmental Sciences Unit 1; CUET-UG Environmental Studies
Environmental science is the study of the natural world and of human interactions with it: how the atmosphere, water, rocks, soils and living things work as one system, what resources they provide, and how population, consumption and technology change them. It draws on biology, chemistry, physics, geology, geography, economics, sociology and ethics, which is why it is taught as a compulsory foundation course in most undergraduate degrees worldwide, including agriculture, and why it opens many environmental science examinations.
This manual is the map of the whole field. It introduces each theme and points to the specialised subjects of this track for depth: ecology and ecosystems, climate, soil, water, biodiversity, pollution, energy, sustainable agriculture, environmental law and governance. Its own focus is the vocabulary, the big numbers, and the main environmental problems that an agricultural graduate meets: resource depletion, land degradation, population and consumption pressure, the side-effects of modern farming, mining and dams, natural disasters, and the ethical and civic responses to them.
It is examined at every level. University entrance tests and first-year environmental studies courses test definitions and facts. Postgraduate entrance examinations in environmental science ask for more detail and simple calculations. Doctoral entrance, research-fellowship and lecturer-eligibility examinations in environmental sciences test fundamentals in depth, often as assertion–reason or matching items. Where figures differ by source, such as land degradation extents or disaster exposure, this manual names the source and date. Examples are drawn from every continent, and figures are global unless a region is named.
Environment means the surroundings of an organism: all the physical, chemical, biological and social factors that affect it. Environmental science studies these surroundings and how they change, while environmental studies adds the social, economic and policy dimensions, and environmental engineering designs technical solutions. The field is multidisciplinary (drawing on many disciplines) and increasingly interdisciplinary (integrating them to solve problems). Modern environmental awareness grew rapidly from the 1960s. Rachel Carson's Silent Spring (1962) documented the harm of pesticides such as DDT to birds and ecosystems. The United Nations Conference on the Human Environment in Stockholm (1972) led to the creation of the United Nations Environment Programme (UNEP), and 5 June became World Environment Day. The World Commission on Environment and Development's report Our Common Future (the Brundtland Report, 1987) defined sustainable development as development that meets the needs of the present without compromising the ability of future generations to meet their own needs. The UN Conference on Environment and Development (the Rio Earth Summit, 1992) produced Agenda 21, the Rio Declaration, and opened the climate change (UNFCCC) and biological diversity (CBD) conventions for signature. In 2015 the UN adopted the 2030 Agenda with 17 Sustainable Development Goals and 169 targets. Many countries have an umbrella environmental protection statute, and several have made environmental education compulsory at every level of schooling, sometimes by court order, in line with the 1977 Tbilisi Declaration. Mehta case (1991) directed that environmental education be taught at all levels, which led to compulsory environmental studies courses in universities. The law and policy subject of this track treats these institutions in depth.
Agriculture is both a beneficiary and a driver of environmental change. It depends on soil, water, climate, pollinators, genetic diversity and pest control by natural enemies, and it occupies about a third of the Earth's ice-free land, uses about 70 per cent of global freshwater withdrawals, and is a major source of greenhouse gases, nutrient pollution, pesticide exposure, deforestation and biodiversity loss. The Green Revolution greatly increased food production but brought groundwater depletion, soil degradation, pesticide and fertiliser overuse, and loss of crop diversity in intensively farmed regions, as chapter 8 explains. An agricultural graduate therefore needs environmental science to diagnose problems on the farm (salinity, erosion, nutrient runoff), to understand regulation and markets (pesticide rules, deforestation-free supply chains, carbon markets), and to design farming systems that remain productive. Later subjects of this track develop each link: soil science for sustainability, hydrology and water quality, climate impacts and adaptation, agricultural greenhouse gas mitigation, nutrient stewardship, pesticides and the environment, agroecology and sustainable farming systems. Environmental problems are typically complex: they involve many interacting causes, long time lags, uncertainty, and costs and benefits that fall on different people. They also cross scales, from a field to a watershed to the planet. Systems thinking, which looks at feedbacks, stocks and flows, and unintended consequences, is therefore a core habit of environmental science, as is the precautionary approach of acting to prevent serious or irreversible harm even when scientific certainty is incomplete.
The Earth system is often described as four interacting spheres. The atmosphere is the envelope of gases held by gravity: by volume about 78 per cent nitrogen, 21 per cent oxygen, 0.93 per cent argon and about 0.04 per cent carbon dioxide, with variable water vapour; its layers, radiation and weather are treated in the atmospheric science subject. It protects life from ultraviolet radiation (through the stratospheric ozone layer), moderates temperature through the greenhouse effect, and distributes heat and water. The hydrosphere is all the Earth's water. Of an estimated total of about 1.39 billion km³, about 97.5 per cent is saline, mostly in the oceans, and only about 2.5 per cent is fresh. Of the fresh water, roughly 69 per cent is locked in glaciers and ice caps, about 30 per cent is groundwater, and only around 1 per cent is in lakes, rivers, soil moisture, the atmosphere and living things. Accessible fresh surface water is therefore a tiny fraction of the total. Water moves through the hydrological cycle of evaporation, transpiration, condensation, precipitation, infiltration, runoff and groundwater flow, driven by solar energy and gravity; the hydrology subject develops it. The lithosphere is the rigid outer shell of the Earth, comprising the crust and the uppermost mantle, broken into tectonic plates whose movement causes earthquakes, volcanoes and mountain building. The crust is dominated by oxygen (about 46 per cent by mass) and silicon (about 28 per cent), followed by aluminium, iron, calcium, sodium, potassium and magnesium. Rocks are igneous (from cooled magma, such as granite and basalt), sedimentary (from deposited and cemented particles, such as sandstone, shale and limestone) or metamorphic (transformed by heat and pressure, such as marble, slate and gneiss), linked by the rock cycle. Weathering of rocks produces soil, the thin, living interface on which agriculture depends; the soil subject treats it.
The biosphere is the zone where life exists, from deep ocean sediments and rocks to the lower atmosphere, together with all living organisms. Life is concentrated in a thin layer near the surface. The biosphere transforms the other spheres: photosynthesis produced the oxygen in the atmosphere over billions of years, organisms build soils and limestone, and vegetation shapes local climate and the water cycle. The Earth is about 4.5 billion years old, and life has existed for more than 3.5 billion years. The spheres interact through flows of energy and matter. Solar energy enters the system and drives weather, the water cycle and photosynthesis, and is ultimately radiated back to space as heat; energy flows through, while matter, apart from small exchanges with space, cycles within the Earth system. Biogeochemical cycles of carbon, nitrogen, phosphorus, sulphur and water link the living and non-living components and are treated in the ecology subject. Human activity now affects all four spheres at planetary scale: changing atmospheric composition and climate, depleting and polluting water, moving more sediment and rock than natural processes in many regions, and reshaping the biosphere through land use and species loss. Many scientists use the term Anthropocene for this era of human dominance, though its formal adoption as a geological epoch was rejected by the relevant stratigraphic body in 2024. The planetary boundaries framework (Rockström and colleagues, 2009, updated 2015 and 2023) identifies nine Earth-system processes, including climate change, biosphere integrity, biogeochemical flows of nitrogen and phosphorus, land-system change and freshwater change, and estimates safe limits; several are assessed to have been crossed.
The environment has abiotic (non-living), biotic (living) and social components. Abiotic factors are often grouped as climatic (light, temperature, precipitation, humidity, wind), edaphic (soil properties such as texture, structure, pH, organic matter, nutrients and moisture), topographic or physiographic (altitude, slope, aspect) and, in water, hydrological and chemical factors (salinity, dissolved oxygen, currents). These set the conditions within which organisms live. Liebig's law of the minimum states that growth is controlled by the scarcest resource relative to need, not by the total of resources, and Shelford's law of tolerance states that each species can survive only within a range of each factor, between a minimum and a maximum, with an optimum in between; species with wide ranges are called eury- (such as eurythermal) and those with narrow ranges steno- (such as stenohaline). Biotic components are the living organisms, classified by their role. Producers (autotrophs), mainly green plants, algae and cyanobacteria, make organic matter from inorganic substances using sunlight (photosynthesis) or, in some bacteria, chemical energy (chemosynthesis). Consumers (heterotrophs) obtain energy by eating other organisms: herbivores (primary consumers), carnivores (secondary and tertiary consumers) and omnivores. Decomposers and detritivores, chiefly bacteria and fungi together with earthworms, termites and other soil animals, break down dead matter and release nutrients for reuse. Without decomposers, nutrients would be locked in dead material and production would stop. The ecology subject develops trophic structure and energy flow.
Humans add a social or cultural environment: population and settlements, economic systems, technology, institutions, laws, cultural values, religion, knowledge and politics. These shape how people use resources and how much they affect the natural environment. The same natural resource, such as a river, may be managed sustainably or degraded depending on property rights, prices, governance, and cultural norms. Indigenous and local knowledge systems often contain detailed understanding of local ecosystems and practices, such as sacred groves in South Asia, West Africa and East Africa (the kaya forests of coastal Kenya, for example) that have conserved forest patches for generations. Environmental problems therefore have social causes and social consequences. Poverty can force people to overuse resources for survival, while affluence drives high consumption and waste; both pressures appear in the IPAT identity discussed in chapter 6. The burden of pollution and degradation often falls on poor and marginalised groups who contributed least to it, which is the concern of environmental justice. Gender affects roles in resource collection and management, as the transitions and governance subject explains. An integrated view treats the environment as a social–ecological system in which people and nature are coupled: changes in one affect the other through feedbacks. For example, falling groundwater tables raise pumping costs, which can push smallholders into debt, leading to further pressure on resources. Recognising such feedbacks helps design interventions that address root causes rather than symptoms.
A natural resource is anything obtained from the environment to meet human needs. Resources are classified as renewable (replenished by natural processes within human time scales, such as sunlight, wind, water, forests, fish and soil fertility if managed well) and non-renewable (formed over geological time and effectively finite, such as fossil fuels and minerals). Renewable resources become depletable if used faster than they regenerate, so the distinction depends on management. Some resources are inexhaustible flows (solar energy), and some non-renewable resources can be recycled (metals). Land is the base of agriculture, forests, settlements and infrastructure. Of the world's roughly 13 billion hectares of land, about 1.5–1.6 billion hectares (about 12 per cent) are cropland and roughly 3 billion hectares are permanent meadows and pastures (FAO); land per person differs enormously between densely populated regions such as South and East Asia and land-rich regions such as Oceania and the Americas. Competition among agriculture, urban expansion, industry, infrastructure, forests and conservation is intense. Soil forms very slowly, often taking centuries to form a few centimetres, so soil lost to erosion is practically non-renewable on human time scales. Healthy soils supply nutrients and water, store carbon, filter water and host much of the Earth's biodiversity; the soil subject develops these functions. Freshwater is unevenly distributed in space and time. Freshwater is just as unevenly shared: Asia holds roughly 60 per cent of the world's people but about a third of its renewable freshwater, while South America holds about a quarter of the freshwater for under 6 per cent of the people, and monsoon regions receive most of their rain in a few months. A widely used indicator, the Falkenmark index, classifies a country as water-stressed when annual renewable freshwater per person falls below 1700 m³, water-scarce below 1000 m³, and in absolute scarcity below 500 m³. Groundwater supplies a large share of irrigation worldwide and is over-exploited in many aquifers, such as the North China Plain, the High Plains (Ogallala) aquifer and parts of the Middle East and South Asia; the water subjects treat this.
Forests provide timber, fuel, fodder, food and medicines, and regulate water, climate, soil and biodiversity. Global forest area is about 4 billion hectares, roughly 31 per cent of land, and deforestation, mainly for agricultural expansion in the tropics, continues, though its rate has slowed according to FAO's Global Forest Resources Assessments. Forest cover differs greatly between countries, from over 60 per cent of land in parts of Scandinavia, Central Africa and Amazonia to under 1 per cent in many arid states; national forest inventories report it at regular intervals to FAO's Global Forest Resources Assessment, and many national forest policies set a target share of land under forest or tree cover. Indicators of forest quality, such as canopy density, matter as well as area. Mineral resources include metallic ores (iron, copper, aluminium from bauxite, zinc), non-metallic minerals (limestone, gypsum, phosphate rock, mica) and fuel minerals (coal, uranium). Minerals underpin construction, industry, fertilisers (phosphate and potash), electronics and the energy transition. Extraction has major environmental and social impacts, discussed in chapter 9. Recycling, substitution and efficient use extend mineral resources. Energy resources include fossil fuels, nuclear fuels and renewable flows such as solar, wind, hydro, biomass, geothermal and tidal energy. Their environmental impacts and the energy transition are treated in the energy subject. The central sustainability principles for resources were summarised by Herman Daly: renewable resources should be harvested no faster than they regenerate; wastes should be emitted no faster than the environment can assimilate them; and non-renewable resources should be depleted no faster than renewable substitutes are developed.
Land degradation is the reduction or loss of the biological or economic productivity of land through human activities and natural processes. The UN Convention to Combat Desertification (UNCCD, 1994) defines desertification as land degradation in arid, semi-arid and dry sub-humid areas resulting from various factors, including climatic variations and human activities; it does not mean the advance of sand dunes alone. Processes include water erosion (sheet, rill and gully erosion, and ravines), wind erosion, chemical degradation (salinisation, sodification, acidification, nutrient depletion, pollution), physical degradation (compaction, waterlogging, crusting), biological degradation (loss of vegetation and soil organic matter), and mass movement such as landslides. Causes include deforestation, overgrazing, unsuitable cultivation of steep or marginal land, poor irrigation and drainage (which cause waterlogging and salinity), excessive or unbalanced fertiliser use, mining, urban sprawl and climate extremes. Estimates of degraded land vary with methods and definitions. National assessments, mostly based on satellite mapping, commonly find that a fifth to a third of a country's land is degrading, and in most humid and semi-arid countries water erosion is the most extensive process, followed by vegetation degradation and wind erosion; the UNCCD asks parties to report three indicators: land cover, land productivity and soil organic carbon. Many national remote sensing agencies map degraded land classes such as gullied and ravinous land, scrubland, waterlogged and saline areas and degraded forest, giving a baseline for reclamation programmes. Globally, UNCCD and other assessments estimate that a large share of land is degraded, though figures differ widely between studies.
Reclamation methods depend on the process. Eroded land is treated with soil and water conservation measures: contour bunding, terracing, check dams and gully plugs, vegetative barriers, cover crops, agroforestry and afforestation, ideally planned across whole watersheds. Ravines, such as those on the Loess Plateau of China, in the Sahel and along the alluvial rivers of South Asia, are stabilised with peripheral bunds, gully plugs, check dams and vegetation. Saline soils, with high soluble salts (electrical conductivity of the saturation extract above 4 dS m⁻¹), are reclaimed by leaching with good-quality water and providing drainage, including subsurface drainage. Sodic (alkali) soils, with high exchangeable sodium (exchangeable sodium percentage above 15) and often high pH, are reclaimed by applying gypsum (calcium sulphate), which replaces sodium on the exchange complex, followed by leaching, and by growing tolerant crops such as rice and salt-tolerant grasses; National soil salinity research centres in Asia, the Middle East and Australia have developed widely adopted technologies, and FAO's Global Soil Partnership compiles them. Acid soils are ameliorated with lime. Waterlogged land needs drainage and sometimes bio-drainage with deep-rooted trees. Mined land is restored by backfilling, topsoil replacement and revegetation. Sustainable Development Goal target 15.3 calls for achieving a land degradation-neutral world by 2030. Land degradation neutrality (LDN) means that the amount and quality of land resources remain stable or increase within specified scales and time frames, achieved by avoiding new degradation, reducing existing degradation and reversing it through restoration. Countries have pledged to restore around a billion hectares in total under the UNCCD, the Bonn Challenge and the UN Decade on Ecosystem Restoration (2021–2030). Restoration has strong co-benefits for livelihoods, water, biodiversity and climate, but success depends on community participation, secure tenure, maintenance and choosing native species suited to the site. The land degradation and soil conservation subject of this track treats engineering and policy in depth.
The human population grew slowly for most of history and then very rapidly after about 1800, reaching 1 billion around 1804 and 8 billion on 15 November 2022 according to United Nations estimates. In 2023 the most populous country changed for the first time in modern records on UN estimates, a sign of how fast fertility has fallen in East Asia. Global growth rates peaked at over 2 per cent a year in the late 1960s and have since fallen below 1 per cent; the UN's World Population Prospects project that world population will peak during this century, though projections are uncertain. When a population grows at a constant percentage rate, growth is exponential, and the doubling time is approximately 70 divided by the percentage growth rate (the 'rule of 70'): a growth rate of 2 per cent a year doubles a population in about 35 years. Exponential growth cannot continue indefinitely in a finite environment, which is the basis of concerns going back to Thomas Malthus (1798), who argued that population tends to grow geometrically while food supply grows arithmetically. Malthus did not foresee the large increases in agricultural productivity that followed, but his concern about limits recurs in modern debates. The demographic transition model describes how countries move from high birth and death rates (stage 1), through falling death rates with continued high birth rates and rapid growth (stage 2), to falling birth rates (stage 3), and to low birth and death rates with slow or no growth (stage 4); some models add a stage 5 with declining population. The total fertility rate (TFR) is the average number of children a woman would have over her lifetime at current age-specific rates; replacement level is about 2.1 in low-mortality populations. Global TFR fell from about 5 in 1950 to about 2.3 in 2021 (UN); it is below 1.5 in much of East Asia and southern Europe and above 4 in much of sub-Saharan Africa, and national averages hide wide differences between regions. Age structure diagrams show whether a population is expanding (a broad base), stable or contracting. Population momentum means that a young population continues to grow for decades even after fertility falls to replacement.
Environmental impact depends not only on the number of people but on how much each person consumes and how that consumption is produced. The IPAT identity, proposed by Paul Ehrlich and John Holdren (1971) in debate with Barry Commoner, expresses this as I = P × A × T: impact equals population times affluence (consumption or output per person) times technology (impact per unit of consumption or output). For example, if population grows by 20 per cent, affluence by 50 per cent and technology reduces impact per unit by 30 per cent, impact changes by a factor of 1.2 × 1.5 × 0.7 = 1.26, a 26 per cent increase. The Kaya identity applies the same logic to carbon dioxide emissions: CO2 = population × (GDP per person) × (energy per unit of GDP) × (CO2 per unit of energy). It shows that emission reductions must come from lower energy intensity and lower carbon intensity of energy if population and income keep growing. IPAT is an identity, not a causal model: the factors are not independent, since technology may change with affluence, and population growth may slow as incomes rise. The STIRPAT model (Dietz and Rosa) turns it into a statistical model that tests the influence of each factor. The global distribution of consumption is very unequal: a small share of the world's population in high-income countries accounts for a large share of resource use and emissions, while many people in low-income countries consume very little. This means that consumption patterns and technology, not population alone, determine much of the environmental impact, an important point for both policy and ethics. Decoupling economic growth from resource use and environmental impact, relatively (impact grows more slowly than the economy) or absolutely (impact falls while the economy grows), is a central goal of sustainable development.
Carrying capacity is the maximum population of a species that an environment can support indefinitely without degrading it, given the resources available. In population ecology it appears as the parameter K in the logistic growth model, as the ecology subject explains. For livestock and wildlife, carrying capacity is used to set stocking rates: grazing more animals than the land can support degrades pasture and soil, and stocking rates must adjust to rainfall and forage production. For humans, carrying capacity is harder to define because it depends on technology, trade, consumption levels and values. Trade allows a region to draw on the carrying capacity of distant places. Instead of asking how many people the Earth can carry, environmental scientists often ask how much productive area a given population's consumption requires, which leads to the ecological footprint.
The ecological footprint, developed by Mathis Wackernagel and William Rees in the early 1990s, measures the biologically productive land and water area required to produce the resources a population consumes and to absorb its wastes, chiefly carbon dioxide from fossil fuels, given prevailing technology. It is expressed in global hectares (gha), hectares with world-average biological productivity. Biocapacity is the productive area actually available, also in global hectares. When a population's footprint exceeds the biocapacity available to it, it runs an ecological deficit, met by imports, by depleting stocks or by accumulating waste such as carbon dioxide in the atmosphere. The Global Footprint Network estimates that humanity's footprint exceeds the Earth's biocapacity by roughly 70 per cent, meaning that humanity uses resources as if it had about 1.7 Earths. Earth Overshoot Day marks the date each year when humanity's demand exceeds what the Earth can regenerate in that year; in recent years it has fallen in late July or early August. The number of Earths needed is the footprint per person divided by the biocapacity per person: a footprint of 2.7 gha per person against 1.6 gha of biocapacity per person implies about 1.7 Earths. Footprints per person differ greatly between countries, with high-income countries far above the world average and many low-income countries below it per person, although a populous low-income country can still have a large total footprint. The carbon footprint, the largest component of the global ecological footprint, is now often measured separately in tonnes of CO2-equivalent, as in the life-cycle assessment and carbon accounting subjects. The water footprint, developed by Arjen Hoekstra, measures the volume of water used to produce goods and services, divided into green (rainwater), blue (surface and groundwater) and grey (water needed to dilute pollution) components; the water conservation subject uses it. Footprint methods have limitations: they aggregate diverse impacts into one area measure, depend on assumptions about yields and carbon absorption, omit some impacts such as toxic pollution and biodiversity loss, and should be read as communication and comparison tools rather than precise measures. Their value lies in showing that current global consumption exceeds what ecosystems can regenerate.
World food production has more than kept pace with population growth since the 1960s, largely because of higher yields rather than more land. The Green Revolution, associated with Norman Borlaug (Nobel Peace Prize 1970) and the international research centres CIMMYT in Mexico and IRRI in the Philippines, combined high-yielding semi-dwarf varieties of wheat and rice with irrigation, chemical fertilisers and pesticides from the mid-1960s. It turned several Asian and Latin American countries from food-deficit importers into countries with large grain stocks and greatly reduced famine risk, though it largely bypassed sub-Saharan Africa. Yet hunger and malnutrition persist, mainly because of poverty, inequality, conflict and waste rather than global shortage, and the food system faces growing demand, changing diets and climate change. FAO estimated in 2011 that roughly one-third of food produced for human consumption is lost or wasted; later estimates separate food loss from harvest up to retail (FAO, about 13–14 per cent) and food waste at retail, food service and household levels (UNEP's Food Waste Index, about 17–19 per cent of food available to consumers). The sustainable food systems subject develops these issues.
Intensive agriculture has caused serious environmental problems, especially in intensive Green Revolution regions such as the rice–wheat belt of South Asia and the North China Plain. Groundwater depletion follows heavy pumping for rice–wheat systems; water tables have fallen by many metres in parts of South Asia and northern China, raising pumping costs and energy use. Waterlogging and secondary salinisation occur in canal-irrigated areas with poor drainage. Fertiliser overuse and imbalance, especially high nitrogen relative to phosphorus and potassium, lower nutrient use efficiency, contaminate groundwater with nitrate and cause eutrophication of lakes and rivers when nitrogen and phosphorus run off; algal blooms and oxygen depletion follow. Pesticide overuse harms non-target organisms, including pollinators and natural enemies, leads to pest resistance and resurgence, and leaves residues in food, water and soil. Monocultures and the replacement of traditional varieties have caused genetic erosion, the loss of crop genetic diversity. Soil degradation includes declining organic matter, micronutrient deficiencies (zinc deficiency became widespread in rice–wheat soils), compaction and erosion. Burning of crop residues, such as rice straw in South Asia, sugarcane trash in Brazil and stubble in parts of Africa and Eastern Europe, releases particulate matter and contributes to severe seasonal air pollution, along with loss of nutrients and soil organisms. Agriculture also contributes greenhouse gases: methane from rice paddies and livestock, nitrous oxide from fertilised soils, and carbon dioxide from land clearing; it drives most tropical deforestation globally. Responses include integrated nutrient management and soil-test-based fertiliser use, integrated pest management, micro-irrigation and crop diversification away from water-hungry rice in over-pumped areas, residue retention with machines such as the Happy Seeder instead of burning, conservation agriculture, organic and natural farming in suitable contexts, and agroecological approaches. These are developed in the nutrient stewardship, pesticides, conservation agriculture, organic farming, agroecology and sustainable farming systems subjects.
Mining extracts minerals and fuels from the Earth by surface (open-cast or open-pit) or underground methods. Its environmental effects include clearing of forests and topsoil; disturbance of large areas of land by pits, overburden dumps and tailings; loss of biodiversity and habitat fragmentation; air pollution from dust and blasting; water pollution, including acid mine drainage, which forms when sulphide minerals such as pyrite are exposed to air and water and produce sulphuric acid that mobilises heavy metals; lowering of water tables by pit dewatering; land subsidence over underground workings; mine fires in coal fields, some of which have burned for decades (Centralia in Pennsylvania since 1962, Jharia in South Asia for over a century); noise; and health effects such as silicosis and pneumoconiosis among workers. Tailings dams can fail catastrophically; the collapse of a tailings dam at Brumadinho, Brazil, in 2019 killed over 250 people. Mining also causes social impacts: displacement of communities, often Indigenous or tribal peoples in forested mineral-rich regions of Asia, Africa, Latin America and Australia, loss of livelihoods, and conflicts over land and benefits. Responses include environmental impact assessment and clearances, progressive mine closure and reclamation plans, backfilling and revegetation, treatment of mine water, dust suppression, and benefit-sharing with affected communities. Many mining laws now require benefit sharing, through community development agreements, royalties earmarked for affected districts or local development funds paid by leaseholders, and the Extractive Industries Transparency Initiative (EITI) asks countries to publish what companies pay.
The International Commission on Large Dams (ICOLD) defines a large dam as one 15 metres or more in height from the lowest foundation to the crest, or between 5 and 15 metres impounding more than 3 million cubic metres. Dams provide irrigation, hydropower, flood control, drinking water and navigation; large dams in Asia, Egypt and the western United States were central to the expansion of irrigation, and in Asia to the Green Revolution; ICOLD's register lists about 60,000 large dams worldwide. Their environmental and social costs are also large. Reservoirs submerge forests, farmland and villages, displacing people: estimates of the number displaced by large dams worldwide run into tens of millions, and resettlement and rehabilitation have often been inadequate, as in the controversies over the Three Gorges dam in China, the Aswan High Dam in Egypt, the Sardar Sarovar dam in South Asia and the Pak Mun dam in Thailand; such disputes led the World Bank and IUCN to convene the World Commission on Dams, which reported in 2000. Dams fragment rivers, block fish migration and alter downstream flows, temperature and sediment, reducing the fertility of floodplains and deltas and contributing to coastal erosion and subsidence. Reservoirs trap sediment and gradually lose storage capacity through siltation. Stagnant reservoirs can favour waterborne disease vectors and, in the tropics, emit methane. Waterlogging and salinity can develop in poorly drained command areas. Large reservoirs can trigger earthquakes, a phenomenon called reservoir-induced seismicity; the magnitude 6.3 earthquake at Koyna reservoir in 1967 and the Kremasta (Greece) and Kariba (Zambia–Zimbabwe) events of the 1960s are frequently cited examples. Dam failures, though rare, can be catastrophic. The World Commission on Dams (2000) recommended that decisions on dams should consider alternatives, gain public acceptance with the free, prior and informed consent of affected Indigenous peoples, address existing dams' problems, sustain rivers and livelihoods, recognise entitlements and share benefits, ensure compliance, and share rivers peacefully. Alternatives and complements include smaller decentralised water harvesting structures, improved efficiency of existing irrigation, run-of-river hydropower and environmental flow releases. The environmental impact assessment and water governance subjects treat assessment and management in detail.
A natural hazard becomes a disaster when it seriously disrupts a community that is exposed and vulnerable, as the adaptation and disaster risk subject explains with the Sendai Framework. Exposure to hazards is global but uneven: UNDRR reports that floods and storms account for most recorded disasters and Asia for most people affected. National disaster management plans, prepared under the Sendai Framework for Disaster Risk Reduction 2015–2030, typically map the share of land prone to earthquakes, floods and river erosion, the length of coast exposed to cyclones and tsunamis, the share of cropland vulnerable to drought, and the hill areas at risk from landslides and avalanches; large monsoon and delta countries often find more than half their land exposed to at least one major hazard. Floods may be riverine (from prolonged heavy rain over catchments, as in the Ganges–Brahmaputra, Yangtze, Mississippi and Niger basins), flash floods (rapid, from intense local rain or cloudbursts, especially in mountains), coastal (from storm surges), urban (from heavy rain overwhelming drainage on paved surfaces) or from dam or glacial lake outbursts. Droughts are meteorological, agricultural, hydrological or socioeconomic, as the adaptation subject explains; they develop slowly and affect large areas and livelihoods. Tropical cyclones bring wind, storm surge and heavy rain to coasts, especially the Bay of Bengal, the Philippines, the Caribbean, Mozambique and Madagascar; their meteorology is covered in the atmospheric science subject.
Earthquakes result from sudden release of energy along faults, mostly at tectonic plate boundaries; the Himalaya, formed by a continental collision between two plates, is one of the most seismically active regions. The point of rupture underground is the focus or hypocentre, and the point on the surface above it is the epicentre. Magnitude measures the energy released; the moment magnitude scale has largely replaced the Richter scale for large earthquakes. Both are logarithmic: each increase of one unit corresponds to a tenfold increase in measured wave amplitude and roughly 32 times more energy released. Intensity, measured on scales such as the Modified Mercalli scale, describes the effects at a particular place and depends on distance, depth, geology and building quality. National building codes divide territory into seismic zones by expected ground shaking, usually expressed as peak ground acceleration with a 10 per cent chance of exceedance in 50 years, and the most severe zones lie along plate boundaries and active faults; ISO 3010 sets the basis for seismic actions on structures. Building codes, retrofitting and land-use planning are the main ways to reduce earthquake losses, because buildings, not ground shaking itself, cause most deaths. Tsunamis are long-wavelength sea waves generated mainly by undersea earthquakes that displace the sea floor; the Indian Ocean tsunami of 26 December 2004, triggered by a magnitude 9.1 earthquake off Sumatra, killed around 230,000 people in more than a dozen countries, including Indonesia, Sri Lanka, India, Thailand and countries as far as Somalia. It led to an ocean-wide tsunami warning system coordinated by UNESCO's Intergovernmental Oceanographic Commission, with regional tsunami service providers in Australia, India and Indonesia, modelled on the Pacific system set up after 1960. Landslides are downslope movements of rock, debris or soil, triggered by heavy rain, earthquakes, undercutting by rivers or roads, deforestation and slope loading; young mountain ranges such as the Himalaya, Andes and Alps and steep humid uplands are especially prone, and landslides often follow intense monsoon or typhoon rains. Mitigation includes hazard zonation mapping, drainage, slope stabilisation, retaining structures, vegetation and controlling construction on unstable slopes. For agriculture, disasters destroy crops, livestock, soils and infrastructure; preparedness and recovery in agriculture are covered in the adaptation subject.
Environmental ethics asks what moral obligations humans have towards nature, other species and future generations. Anthropocentrism holds that only humans have intrinsic moral value, so nature matters instrumentally, for the services and resources it provides; enlightened anthropocentrism still supports strong protection because human wellbeing depends on healthy ecosystems. Biocentrism extends moral consideration to all living organisms; Albert Schweitzer's 'reverence for life' and Paul Taylor's respect for nature are examples. Ecocentrism values ecological wholes, such as species, ecosystems and the biosphere; Aldo Leopold's 'land ethic' in A Sand County Almanac (1949) states: 'A thing is right when it tends to preserve the integrity, stability, and beauty of the biotic community. It is wrong when it tends otherwise.' Deep ecology, a term coined by the Norwegian philosopher Arne Naess (1973), argues for the intrinsic value of all life and for fundamental changes in human values and lifestyles, in contrast to 'shallow' ecology focused on pollution and resource depletion for human benefit. Other ethical principles shape environmental policy. Intergenerational equity holds that present generations must not deprive future ones of a healthy environment. The precautionary principle (Principle 15 of the Rio Declaration, 1992) states that where there are threats of serious or irreversible damage, lack of full scientific certainty shall not be used as a reason for postponing cost-effective measures to prevent environmental degradation. The polluter pays principle (Principle 16) holds that the polluter should bear the cost of pollution. Environmental justice demands a fair distribution of environmental benefits and burdens. Many religious and cultural traditions, including sacred groves and sacred rivers in South Asia and Africa, the Andean concept of Pachamama and the conservation practices of desert communities that protect trees and wild animals, express respect for nature.
Citizens and civil society play central roles in environmental protection. More than 100 national constitutions now recognise a right to a healthy environment, a duty of the state to protect it, or both, and some add a citizen's duty to protect nature; Ecuador's 2008 constitution goes further and gives rights to nature itself. Where no express right exists, courts in several countries have read the right to life to include a clean and healthy environment, and in 2022 the UN General Assembly (resolution 76/300) recognised the human right to a clean, healthy and sustainable environment; public interest litigation and open standing rules have let citizens bring cases on industrial pollution, vehicle emissions, river cleaning, forest conservation and climate. More than 2,000 specialised environmental courts and tribunals now operate in over 60 countries (UNEP, 2021), and the Aarhus Convention (Europe) and Escazú Agreement (Latin America and the Caribbean) guarantee access to information, participation and justice. The law and policy subject treats these in detail. Non-governmental organisations (NGOs) and community movements raise awareness, conduct research, monitor pollution and compliance, litigate, advocate for policy change, support communities and implement conservation and development projects. Examples range from grassroots movements such as Kenya's Green Belt Movement and the Chipko tree-hugging movement in the Himalaya to national research and advocacy organisations and international organisations working on conservation, climate and development. Their legitimacy depends on transparency, accountability and genuine connection with affected people. Individual citizens contribute by reducing their own consumption and waste, choosing sustainable products, conserving water and energy, participating in local governance, such as village-level or community natural resource management, joining citizen science projects that monitor birds, water quality or air pollution, and holding governments and companies to account. Environmental education aims to build knowledge, attitudes and skills for such participation, in line with the Tbilisi Declaration and SDG target 4.7.
A student uses this subject as the map for all later environmental and sustainability courses, learning the core vocabulary (biotic and abiotic components, renewable and non-renewable resources, carrying capacity, footprint, land degradation, IPAT) and the landmark dates and documents that examiners ask about: Silent Spring, Stockholm 1972, Brundtland 1987, Rio 1992 and the SDGs. Simple calculations recur: rule-of-70 doubling times, IPAT and Kaya factor changes, the number of Earths from footprint and biocapacity, Falkenmark water classes and earthquake energy ratios.
A five-year practitioner, such as an agricultural officer, an environmental consultant or an NGO field manager, uses the subject to frame problems for colleagues and communities: explaining why groundwater is falling, why a field is turning saline or sodic and what reclamation it needs, how a proposed mine or dam will affect land, water and livelihoods, and how disaster exposure shapes a district plan. The foundation makes it possible to draw on the right specialised subject and specialist.
A senior professional with 25 years' experience, such as a state environment or agriculture secretary, a research director or a corporate sustainability head, uses the subject's system view to set priorities across resources, to recognise trade-offs between food, water, energy and biodiversity, to weigh population, consumption and technology in long-term planning, and to apply ethical and legal principles such as precaution, polluter pays and intergenerational equity in decisions about land, mining and dams.
A researcher with a PhD and 25 years' experience uses the fundamentals to frame interdisciplinary research on social–ecological systems, planetary boundaries, footprints and decoupling, land degradation neutrality and restoration, and the environmental history of agricultural intensification. Such a researcher also teaches the foundation course and ensures that its numbers and definitions are kept current with new assessments.
This manual is a survey: each theme is treated in depth in a specialised subject of this track, to which it refers. Statistics change with each assessment: population, forest cover, degraded land, food loss and footprint figures should be updated from the latest UN, FAO, UNCCD and Global Footprint Network releases, and disaster exposure figures come from national documents that are periodically revised. It does not give country-by-country figures, detailed soil reclamation dose calculations (left to the land degradation and soil subjects), or engineering design of dams and mine reclamation. Ethical theories are summarised briefly without the philosophical debates around them.
Original practice questions written to the syllabus and pattern of the exams named in each question's examTags. They are not past papers and do not reproduce any board's questions.
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