49 of the ESS glossary’s terms, each with the part of the syllabus where you first meet it.
A computer model of an imaginary planet with black and white daisies, published by Watson and Lovelock in 1983, showing how negative feedback through albedo can regulate a planet's temperature.
A barrier built across a river to hold back water, creating a reservoir used for water supply, irrigation, flood control or hydroelectric power.
The IUCN Red List category for species with too little information on distribution or population to assess their extinction risk; it does not mean that the species is safe.
An electronic device that records measurements from one or more sensors automatically at set time intervals, allowing conditions to be monitored continuously over long periods.
An investigation that answers its research question using secondary data selected from a database by stated, repeatable rules for filtering and sampling.
Dichlorodiphenyltrichloroethane, a persistent, fat-soluble organochlorine insecticide that biomagnifies in food chains; its breakdown product DDE causes eggshell thinning in birds of prey.
The remains of dead plants, animals and microorganisms, together with their wastes such as faeces and manure, before they are fully decomposed.
An area of a sea or lake where the water, usually near the bottom, is hypoxic or anoxic, so that it cannot support most aquatic animal life.
The process of reducing or ending the use of energy sources that emit carbon dioxide, such as fossil fuels, and replacing them with low-carbon or renewable sources.
An organism, mainly a bacterium or fungus, that breaks down dead organic matter into inorganic substances, releasing nutrients back into the soil, water or air.
The breakdown of dead organic matter into simpler inorganic substances by decomposers and detritivores, which releases nutrients and carbon dioxide.
Breaking the link between economic activity and environmental pressure, so that output or well-being can rise while resource use or pollution stays the same or falls.
An ecocentric philosophy, named by Arne Næss in 1973, holding that all life has value in itself, irrespective of its usefulness to humans, and calling for deep changes in human society.
A facility for the permanent disposal of high-level radioactive waste, built hundreds of metres underground in stable rock, where engineered and natural barriers isolate the waste for thousands of years.
The clearing of forest and conversion of the land to another use, such as farming, mining or settlement, removing the forest's storages of biomass and much of its diversity.
A number, calculated from the sample size and the number of groups or categories, used to find the critical value of a statistical test.
A planned, democratic reduction of production and consumption, especially in high-income countries, to bring ecological footprints within biocapacity while improving well-being and equity.
A period of potential economic growth when falling fertility leaves a population with a large share of working-age people relative to dependants.
A model describing how the birth and death rates of a population change through five stages as a society develops, from high and fluctuating rates to low rates, with rapid growth in between.
The study of human populations: their size, structure, distribution and change through births, deaths and migration.
The dating of past events and the reconstruction of past climate from the pattern of annual growth rings in trees, which are wider in favourable years and narrower in poor ones.
The conversion of nitrate back into nitrogen gas by denitrifying bacteria in anaerobic conditions such as waterlogged soils, returning nitrogen to the atmosphere.
A factor whose effect on a population's birth or death rate increases as population density increases, such as competition, predation and disease.
A factor whose effect on a population does not depend on its density, such as extreme weather, fire, floods or volcanic eruptions.
The number of dependants (people aged under 15 and 65 and over) for every 100 people of working age (15–64) in a population.
The variable that is measured in an investigation because it is expected to change in response to the independent variable; plotted on the y-axis of a graph.
A system in which a small refundable deposit is added to the price of a drink container and paid back when the empty container is returned for reuse or recycling.
The removal of salt and other dissolved minerals from seawater or brackish water to produce freshwater, mainly by reverse osmosis or by distillation.
Land degradation in arid, semi-arid and dry sub-humid areas, caused by climatic variation and human activities such as overgrazing and deforestation, leading to desert-like conditions.
The drying out of an organism or a habitat through loss of water, a major stress for organisms exposed to air at low tide or on dry soils.
An animal that ingests dead organic matter such as fallen leaves, faeces and dead bodies, breaking it into smaller pieces, as earthworms and woodlice do.
The movement of people from large urban areas to smaller towns and rural areas, so that the proportion of the population living in cities falls; also called counter-urbanisation.
An identification tool made of a series of numbered questions, each with two alternative answers that lead either to another question or to the name of an organism.
The unequal heating of the Earth’s surface and atmosphere, mainly because the angle and path length of sunlight vary with latitude, giving an energy surplus in the tropics and a deficit near the poles.
A single-celled protist with two flagella, common in marine plankton; some species form red tides and produce neurotoxins that accumulate in shellfish.
A technology that removes carbon dioxide directly from the surrounding air using chemical filters, after which the gas can be stored underground or used.
The amount of oxygen gas dissolved in water, usually measured in milligrams per litre, which aquatic organisms need for respiration.
An economy designed to share value and opportunity far more equitably among all stakeholders, rather than relying on growth to reduce poverty.
An event, natural or human, such as fire, flood, storm, grazing or clearing, that removes or damages part of a community and changes the resources available.
A single number calculated from sample data that combines species richness and evenness to describe the diversity of a community, used to compare sites or track change over time.
A method of identifying a species by sequencing a short, standard section of its DNA and comparing it with a reference library of sequences from known species.
The unit for the total amount of ozone in a column of atmosphere; 1 DU equals a layer of pure ozone 0.01 mm thick at standard temperature and pressure.
The number of years a population would take to double in size if its current percentage growth rate stayed constant.
A framework for a regenerative and distributive economy that meets the needs of all people within the means of the planet, shown as a ring between a social foundation and an ecological ceiling.
The area of land drained by a river and its tributaries, separated from neighbouring basins by high ground called a watershed.
A method of irrigation that delivers small amounts of water slowly through pipes and emitters directly to the roots of each plant, reducing losses by evaporation and run-off.
A prolonged period of below-average precipitation that leads to a shortage of water for ecosystems, agriculture or human supply.
A crop variety that can grow and produce a yield with less water than usual, through traits such as deep roots or reduced water loss, whether bred conventionally or genetically modified.
The mass of a sample after all its water has been removed by drying to constant mass, used as a measure of the organic matter it contains.