Unit 1: Introduction and sustainable development

Environmental studies examines how living organisms interact with their surroundings and with each other, and how human activity alters those relationships. It emerged as a formal discipline after the mid-20th century (notably the 1972 Stockholm Conference), driven by pollution, resource depletion and biodiversity loss. This unit establishes the physical setting of life on Earth, the nature of the discipline itself, and the sustainability framework used to evaluate human demands on that setting.

• Central concern: the environment as a finite, interconnected life-support system whose stability is threatened by unregulated human demand.
• Guiding logic: understand the system (spheres, components) → recognise the study's breadth (multidisciplinary scope) → apply a limiting principle (sustainability, carrying capacity, SDGs).
• Key convention: "environment" is treated as the sum of biotic and abiotic factors acting on an organism at any point in space and time.

II. The Environment — Composition and Structure

The environment is everything that surrounds and influences an organism; it is analysable into functional components and spatial spheres.

A. Introduction to environment

The word derives from the French environner, meaning "to encircle" or "surround".

• Definition: the totality of physical, chemical and biological factors external to an organism that influence its growth, development and survival.
• Two broad categories:
  • Physical (abiotic): non-living factors — air, water, soil, temperature, light, humidity.
  • Biological (biotic): all living organisms — plants, animals, microbes — and their interactions.
• System property: components are interdependent; a change in one (e.g. rising atmospheric CO₂) propagates through others (ocean acidification, warming).

B. Components of environment

The environment is built from four interacting components, three abiotic and one biotic.

• Atmosphere: the gaseous envelope — ~78% N₂, ~21% O₂, ~0.04% CO₂ plus argon and water vapour; regulates temperature and filters ultraviolet radiation.
• Hydrosphere: all water — oceans (~97% of Earth's water), ice caps, groundwater, rivers, lakes; drives the water cycle and dissolves nutrients.
• Lithosphere: the solid outer crust and upper mantle; source of minerals and the soil layer that anchors terrestrial life.
• Biosphere: the zone where life exists, overlapping the other three; the sum of all ecosystems.
• Linkage: the biosphere depends on inputs from the other three — e.g. photosynthesis draws CO₂ from the atmosphere, water from the hydrosphere and minerals from the lithosphere.

C. Spheres of earth

The physical components correspond to concentric, interacting "spheres" that together form the Earth system.

• Lithosphere: rigid crust plus uppermost mantle, ~100 km thick; broken into tectonic plates.
• Hydrosphere: liquid and frozen water at and near the surface.
  • Cryosphere: frozen sub-part — glaciers, sea ice, permafrost — often treated separately.
• Atmosphere: layered by temperature — troposphere (weather), stratosphere (ozone layer at ~15–35 km), mesosphere, thermosphere.
• Biosphere: the thin habitable film from deep ocean vents to the lower atmosphere.
• Interaction example: the hydrological cycle links all four — solar energy evaporates hydrosphere water into the atmosphere, precipitation returns it to lithosphere and biosphere.

III. Environmental Studies as a Field

Environmental studies is not a single science but an integrative field applied to a wide range of human and natural problems.

A. Multidisciplinary nature of environmental studies

The subject draws on and combines methods from many disciplines because environmental problems cut across natural and social boundaries.

• Natural sciences: ecology and biology supply the study of organisms and ecosystems; chemistry explains pollutant behaviour; physics and geology explain energy flow and Earth processes.
• Applied sciences: environmental engineering designs treatment and control systems; agriculture and soil science address land use.
• Social sciences: economics values resources and analyses costs; sociology and geography study population and settlement; political science and law frame policy and regulation.
• Humanities: ethics questions our duties to nature and future generations.
• Integration point: a single problem such as river pollution requires chemistry (contaminants), biology (aquatic life), economics (clean-up cost) and law (discharge standards) simultaneously.

B. Scope and importance of environmental studies

The field's scope spans local to global scales, and its importance follows from the practical necessity of managing shared resources.

• Scope:
  • Conservation: protection of forests, wildlife and biodiversity.
  • Pollution control: monitoring and abating air, water, soil and noise pollution.
  • Resource management: sustainable use of energy, water, minerals and land.
  • Policy and law: environmental impact assessment, treaties, national statutes.
• Importance:
  • Awareness: builds public understanding of ecological limits and consequences of misuse.
  • Problem-solving: provides tools to address climate change, waste and depletion.
  • Sustainability: guides development that does not exhaust the resource base.
  • Global relevance: transboundary issues (ozone depletion, warming) demand shared knowledge and cooperation.

IV. Sustainability and Sustainable Development

Sustainability is the principle of using resources within the limits of natural regeneration; it operationalises the idea that a finite Earth cannot support unlimited demand.

A. Concept of sustainability

Sustainability is the capacity of a system to endure and maintain its functions indefinitely.

• Core idea: consumption of a renewable resource should not exceed its rate of natural replenishment, and waste generation should not exceed the environment's assimilative capacity.
• Renewable vs non-renewable:
  1. Renewable (forests, fish, solar): sustainable if harvest ≤ regeneration rate.
  2. Non-renewable (fossil fuels, minerals): finite stock; sustainability means efficient use and substitution.
• Intergenerational equity: present use must leave enough for future generations.
• Simple test: a groundwater aquifer used sustainably has extraction balanced by recharge; over-extraction lowering the water table signals unsustainability.

B. Sustainable development

Sustainable development applies sustainability to economic progress, reconciling growth with environmental protection.

• Standard definition (Brundtland Report, Our Common Future, 1987): "development that meets the needs of the present without compromising the ability of future generations to meet their own needs."
• Twin ideas in the definition:
  • Needs: priority to the essential needs of the world's poor.
  • Limits: technology and social organisation impose limits on the environment's ability to meet needs.
• Aim: balance three goals — economic development, social equity and environmental protection — rather than trading one against another.
• Contrast with conventional growth: conventional growth maximises output ignoring depletion and pollution; sustainable development internalises these limits.

C. Carrying capacity

Carrying capacity sets the quantitative ceiling that makes sustainability measurable.

• Definition: the maximum population of a species that a given environment can support indefinitely, given available food, habitat, water and waste absorption.
• Symbol in logistic growth:

dN/dt = rN (1 − N/K)

• N: population size
• r: intrinsic (maximum) growth rate
• K: carrying capacity — the equilibrium population the environment sustains
• Behaviour: growth is fastest at intermediate N and falls to zero as N approaches K, giving an S-shaped (sigmoid) curve.
• Overshoot: if N exceeds K, resource degradation forces the population to crash below K.
• Human dimension: technology and trade raise apparent human carrying capacity, but the ecological footprint measures whether demand exceeds Earth's regenerative capacity.

D. Pillars of sustainability

Sustainability rests on three mutually reinforcing pillars, sometimes drawn as overlapping circles.

• Environmental (planet): protecting ecosystems, biodiversity, air, water and climate; the resource base on which the others depend.
• Economic (profit): maintaining viable, efficient economic activity and livelihoods without exhausting natural capital.
• Social (people): ensuring equity, health, education and community well-being across present and future generations.
• Interaction: true sustainability lies at the intersection of all three; strength in one pillar cannot compensate indefinitely for collapse in another.
• Extended view: some frameworks add a fourth pillar — culture or governance — to capture institutions and shared values.

V. Sustainable Development Goals

The Sustainable Development Goals translate sustainability principles into a shared global agenda with measurable targets.

A. Origin and structure

• Adoption: agreed by all UN member states in 2015 as part of the 2030 Agenda for Sustainable Development, succeeding the Millennium Development Goals.
• Framework: 17 goals and 169 targets covering the three pillars, to be achieved by 2030.
• Organising idea: the goals are "integrated and indivisible" — progress on one supports others; leaving no one behind is the central pledge.

B. The 17 goals by pillar

• Social goals (people):
  • 1 No Poverty; 2 Zero Hunger; 3 Good Health and Well-being; 4 Quality Education; 5 Gender Equality.
• Environmental goals (planet):
  • 6 Clean Water and Sanitation; 13 Climate Action; 14 Life Below Water; 15 Life on Land.
• Economic goals (prosperity):
  • 7 Affordable and Clean Energy; 8 Decent Work and Economic Growth; 9 Industry, Innovation and Infrastructure; 10 Reduced Inequalities; 12 Responsible Consumption and Production.
• Settlement and institutions:
  • 11 Sustainable Cities and Communities; 16 Peace, Justice and Strong Institutions; 17 Partnerships for the Goals.

C. Significance

• Universality: applies to developed and developing countries alike, unlike earlier development targets aimed only at poorer nations.
• Measurability: each target has indicators enabling monitoring of national progress.
• Interlinkage example: achieving Goal 7 (clean energy) advances Goal 13 (climate action) and Goal 3 (health) by cutting fossil-fuel pollution, illustrating how the goals reinforce one another.