Introduction to environmental management

Continents and oceans

Environmental management starts with knowing the map, because every case study you meet sits somewhere specific. The Earth's land surface is grouped into seven continents: Africa, Antarctica, Asia, Europe, North America, South America and Oceania. You must be able to identify and name all seven from a map, and to place them in their correct relative positions, not just recite the list.

The oceans are larger still. Five major oceans cover about 71% of the Earth's surface: the Pacific Ocean, the Atlantic Ocean, the Indian Ocean, the Arctic Ocean and the Southern Ocean. The Pacific is the largest and deepest, and the Southern Ocean is the ring of water that circles Antarctica. Learn the five by linking each one to the land that borders it, so you can label them on an unmarked world map.

A common exam task is a labelled or blank world map where you write the names on the correct shapes. Practise with a blank outline until you can place Antarctica at the bottom, the Arctic Ocean at the top, and the Pacific and Atlantic on either side of the Americas without hesitation. Getting these right is pure recall, so the marks are there for anyone who practises the map.

• Seven continents: Africa, Antarctica, Asia, Europe, North America, South America, Oceania.
• Five oceans: Pacific, Atlantic, Indian, Arctic, Southern.
• Oceans cover about 71% of the Earth's surface; the Pacific is the largest and deepest.
• The Southern Ocean surrounds Antarctica; the Arctic Ocean sits at the top of the world.

Classifying countries by income level

The World Bank groups the world's countries by income, because how much money a country has shapes every environmental decision it can make. It classifies countries using gross national income (GNI) per person, and the syllabus limits you to three groups: low income economies (LICs), middle income economies (MICs) and high income economies (HICs).

LICs are the poorest countries, where most people earn very little and the government has little money to spend. HICs are the richest, with high GNI per person and more money available for everything, including environmental protection. MICs sit between the two, and they are a broad and fast-changing group that includes countries industrialising quickly.

The classification matters for environmental management because a country's income decides which strategies it can afford. A HIC can fund expensive water treatment plants or renewable energy, while a LIC may rely on cheaper, less sustainable options such as burning wood for fuel, so the same environmental problem looks completely different in different income groups.

• LICs: low income economies, with low GNI per person and little money to spend on environmental management.
• MICs: middle income economies, between the two, often industrialising fast.
• HICs: high income economies, with high GNI per person and more resources available.

Sustainability

Sustainability means meeting the needs of the present without compromising the ability of future generations to meet their own needs. The idea is that we must live within what the Earth can keep providing: a resource used today should still be there, in working order, for the people who come after us. The definition comes from the 1987 Brundtland Report, Our Common Future, which put the word into mainstream use.

The need for sustainable management follows directly. Resources such as fresh water, soil, forests and fish stocks are finite, and if we use them faster than they renew, future generations will have less. Sustainable management means using a resource at a rate that lets it recover, so the yield continues year after year rather than running out.

Sustainability is not the same as simply preserving everything untouched. It means using resources wisely so that economic development and a healthy environment can both continue. Overfishing a stock until it collapses is unsustainable because the catches stop; fishing at a rate the stock can replace is sustainable because the catches can go on indefinitely.

• The 1987 Brundtland Report, Our Common Future, gave the definition you quote in the exam.
• Sustainable management uses a resource at a rate it can renew, so the supply continues.
• Unsustainable use, such as overfishing or cutting trees faster than they regrow, runs the resource down.

The water cycle

The water cycle is the continuous movement of water between the oceans, the atmosphere and the land, driven by energy from the Sun. Water evaporates from oceans, lakes and rivers, and plants release water by transpiration. The water vapour rises, cools and condenses into clouds, then falls as precipitation such as rain or snow.

Once precipitation reaches the ground, the paths it takes depend on the surface. Some is caught by leaves and vegetation before it ever touches the soil, which is interception. The rest soaks into the ground by infiltration, then moves slowly downhill through the soil as through-flow and through the rocks below as ground water flow. Water that does not soak in runs over the surface as surface run-off, flowing into rivers and back to the sea, where the cycle begins again.

You must be able to interpret and draw diagrams of the cycle, labelling each process in the right place. Evaporation and transpiration move water up into the air, condensation forms the clouds, precipitation brings it down, and interception, infiltration, surface run-off, through-flow and ground water flow move it through and over the land back towards the sea. A labelled diagram is a reliable source of marks, so learn to draw one from memory.

The atmosphere: composition and layers

The atmosphere is the layer of gases held around the Earth by gravity, and its composition is mostly two gases. Nitrogen makes up about 78% and oxygen about 21%, with the remaining 1% made up of argon (nearly 1%), carbon dioxide (about 0.04%) and water vapour, whose amount varies with the weather and location.

The atmosphere is divided into four primary layers, named from the ground upwards. The troposphere is the lowest layer, where our weather happens and where most of the atmosphere's mass and water vapour sit. Above it is the stratosphere, then the mesosphere, and finally the thermosphere, the outermost layer. Temperature changes with height in each layer, and the boundaries between them are called pauses.

These layers matter for the rest of the course. The ozone layer sits within the stratosphere, and the greenhouse gases that keep the planet warm act mainly in the troposphere. Being able to name the four layers in order, from the ground up, is a common one-mark recall question.

The ozone layer and the natural greenhouse effect

The ozone layer is a region of the stratosphere with a high concentration of ozone gas, O3. Its role is to absorb most of the Sun's harmful ultraviolet (UV) radiation before it reaches the Earth's surface, protecting living things from damage. This is why it is described as a shield: without it, much more UV would reach the surface.

Separate from the ozone layer is the natural greenhouse effect, the process that keeps the Earth warm enough for life. Ultraviolet (shortwave) radiation from the Sun passes through the atmosphere and is absorbed by the Earth's surface. The surface then re-emits some of this energy back into the atmosphere as infrared (longwave) radiation.

Greenhouse gases such as carbon dioxide and water vapour absorb some of this infrared radiation and prevent it from leaving the atmosphere, trapping heat and raising the ambient temperature. This natural effect is essential, because without it the Earth would be far too cold to support life, but the same mechanism is at the heart of the enhanced greenhouse effect and climate change covered later in the course.

Notice the distinction: the ozone layer absorbs incoming ultraviolet radiation, while the greenhouse effect traps outgoing infrared radiation. They happen in different parts of the atmosphere and solve different problems, so do not run them together in an answer.

Ecosystems: structure and interactions

An ecosystem is a community of living organisms interacting with each other and with their non-living environment. Within it, a population is all the individuals of one species living in one place, and a community is all the populations of different species living together. Each species has a habitat, the place where it lives, and a niche, the role it plays, what it eats, where it feeds and when it is active. A biome is the large-scale version: a major region with a characteristic climate and vegetation, such as a tropical rainforest or a desert.

The components of an ecosystem are biotic (living) and abiotic (non-living). Biotic components include producers, which make their own food by photosynthesis, consumers (primary, secondary and tertiary), which eat other organisms, and decomposers, which break down dead material. Abiotic components are the physical and chemical factors, including temperature, humidity, water, oxygen, salinity, light and pH.

Biotic factors control the number and diversity of organisms in an ecosystem through their interactions. Competition occurs when organisms need the same limited resource; it is intra-specific within one species and inter-specific between different species. Grazing is animals feeding on plants, and predation is one animal killing and eating another. These interactions limit population sizes, so the ecosystem settles into a balance rather than one species taking over.

Photosynthesis is the process by which plants synthesise glucose using carbon dioxide, water and energy from sunlight, and it is the energy source that drives nearly every ecosystem on Earth. The word equation is carbon dioxide + water -> glucose + oxygen, and the chemical equation is 6CO2 + 6H2O -> C6H12O6 + 6O2. Chlorophyll, the green pigment inside chloroplasts, captures the light energy, and the rate of the reaction depends on three limiting factors: the availability of water, the concentration of carbon dioxide and the availability of light.

Energy flow through food chains and the carbon cycle

Energy enters an ecosystem when producers capture sunlight, and it passes between organisms along food chains and food webs. A producer is the first level, a primary consumer eats the producer, a secondary consumer eats the primary consumer, and a tertiary consumer eats the secondary consumer. Decomposers break down the dead remains at every level. A trophic level is a feeding level within a food chain, so the producers form level one, primary consumers level two, and so on.

Energy is transferred between organisms starting with a producer, but much of it is lost at every step. Energy is lost through respiration, which releases it as heat, and through waste products and uneaten parts that are not passed on. Only a small fraction, often around 10%, is transferred to the next trophic level, which is why food chains are rarely more than four or five links long.

Aerobic respiration is the chemical process that releases this energy: the reactions in cells that break down glucose molecules and release energy, carbon dioxide and water. The word equation is glucose + oxygen -> carbon dioxide + water, and the chemical equation is C6H12O6 + 6O2 -> 6CO2 + 6H2O. Respiration is, in effect, photosynthesis running backwards, and the two together keep carbon moving around the planet.

The carbon cycle describes this movement of carbon between the atmosphere, living things, the oceans and the rocks. Photosynthesis on land and in the oceans removes carbon dioxide from the atmosphere and locks it into living things as carbon stores, so it has an important effect on atmospheric carbon dioxide concentrations. The stages you must know are photosynthesis, respiration, feeding, decomposition, fossilisation and combustion. Respiration and combustion return carbon dioxide to the atmosphere, while photosynthesis removes it, and over long periods dead organisms can be fossilised into coal, oil and gas.