The ESS glossary

A non-living physical or chemical component of an ecosystem that affects living organisms, such as temperature, light, pH, salinity, dissolved oxygen or soil texture.

A situation in which total environmental pressure, such as emissions or resource use, falls while GDP continues to grow.

The removal of water from a river, lake, reservoir or aquifer by humans, for drinking water, irrigation, industry or energy.

The number of individuals of a species in a given area, or a relative measure of how common it is.

The rules under which users of genetic resources obtain the provider country's prior informed consent and agree terms to share the benefits, such as money or research results.

The closeness of a measurement or result to the true value of the quantity being measured.

The transfer of acids and acid-forming gases and particles from the atmosphere to the ground, either dissolved in precipitation (wet deposition) or as gases and particles (dry deposition).

Rain, snow or fog with a pH below that of unpolluted rain (about 5.6), caused by sulfuric and nitric acids formed from sulfur dioxide and nitrogen oxides in the atmosphere.

A heritable characteristic that increases an organism's chance of surviving and reproducing in its environment, produced over generations by natural selection.

The attraction of water molecules to the molecules of other substances, such as the walls of plant xylem or soil particles.

The horizontal transfer of water vapour, or of the droplets and ice crystals in clouds, by the wind from one place to another.

The movement of air into and out of soil pore spaces, which supplies oxygen to roots and soil organisms and removes carbon dioxide.

A suspension of fine solid particles or liquid droplets in the air, such as dust, sea salt, sulfate droplets or soot, which affects climate by scattering or absorbing radiation and by changing clouds.

The worth people place on natural capital for its beauty and the pleasure of seeing or experiencing it, such as scenic mountains, coasts or lakes.

The planting of trees on land that has not been forested for a long time, or never was, creating a new forest that stores carbon.

A pair of back-to-back horizontal bar graphs showing the number or percentage of males and females in each age group of a population, with the youngest at the base.

A population in which the proportion of older people, usually those aged 65 and over, is rising, because of falling fertility and rising life expectancy.

A non-binding United Nations action plan for sustainable development agreed at the 1992 Rio Earth Summit, to be carried out by governments and organisations from the global to the local level.

Water flowing over or through farmland into streams and lakes, carrying fertiliser nutrients, manure, pesticides and soil particles with it.

A chemical product used in agriculture, such as a synthetic fertilizer, pesticide, herbicide or growth regulator.

A land-use system in which trees or shrubs are grown together with crops or livestock on the same land, to gain from their interactions.

A single number on a fixed scale, calculated from measured concentrations of several pollutants, that communicates how polluted the air is and how much risk it poses to health.

The proportion of incoming solar radiation reflected by a surface, from 0 to 1; snow and ice have a high albedo, dark ocean and forest a low one.

A rapid increase in the population of phytoplankton, such as algae or cyanobacteria, in a water body, usually after an increase in a limiting nutrient, that discolours the water.

A species introduced by human activity, deliberately or accidentally, to an area outside its natural range; also called a non-native or introduced species.

The formation of new species from populations separated geographically, for example by a river, sea or mountain range.

The statement, accepted when a statistical test rejects the null hypothesis, that there is a real difference, correlation or association between the variables studied.

Two or more different conditions in which the same system can persist under similar circumstances, each maintained by its own feedback loops.

The height of a place above sea level; temperature usually falls as altitude increases, producing zones of vegetation on mountains.

The release of aluminium ions from soil minerals into soil water and streams when the soil becomes acidic, where they are toxic to fish, other aquatic organisms and plant roots.

A compound of nitrogen and hydrogen (NH₃) made by nitrogen fixation and by the Haber process; the starting material for most synthetic nitrogen fertilisers.

The release of ammonium from the nitrogen-containing organic compounds in dead organisms and wastes, carried out by decomposers.

The positively charged ion NH₄⁺, formed when ammonia dissolves in soil water; a form of inorganic nitrogen released by decomposition and used by nitrifying bacteria.

Conditions in which oxygen is absent or very scarce, such as waterlogged soils, swamp sediments and animal guts, where only organisms that do not need oxygen can respire.

The breakdown of organic waste by microorganisms in a sealed tank without oxygen, producing biogas (mainly methane) used as fuel and digestate used as fertiliser.

A soil formed on volcanic ash, with a low bulk density, that is often very fertile and supports intensive farming, as in Java and Japan.

The view that animals, or at least sentient animals, have moral rights, such as a right not to be killed or made to suffer, that should not be overridden for human benefit.

The protection of participants' identities in an investigation, so that no response or data can be linked to a named or identifiable person.

Analysis of variance: a statistical test that compares the means of three or more groups by comparing the variation between groups with the variation within them.

The complete absence of dissolved oxygen in water or sediment, in which only anaerobic microorganisms can survive.

A proposed geological epoch in which human activity has become the dominant influence on Earth's environment, climate and life, causing rapid environmental change and species extinction.

An environmental perspective that views humankind as the central and most important element of existence, valuing nature mainly for what it provides to people; it includes careful management and stewardship views.

Caused or produced by human activities, such as the carbon dioxide released by burning fossil fuels, as opposed to arising from natural processes.

The part of the Earth system made or modified by humans, including cities, farmland, infrastructure, industry and the flows of materials they create.

A chemical coating, often containing copper or other biocides, applied to nets, cages and boat hulls to stop algae, barnacles and other organisms growing on them.

A population policy intended to lower the birth rate, for example by providing contraception, setting limits on family size or giving incentives for smaller families.

A predator at the top of a food chain that has no natural predators of its own as an adult, such as the wolf, lion or tiger.

The faulty argument that something is good or right because it is natural, or bad or wrong because it is unnatural.

The farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants, with intervention in the rearing process such as stocking, feeding and protection from predators.

A food production system that combines raising fish with growing plants in water, in which fish waste supplies nutrients to the plants and the plants clean the water returned to the fish.

A body of permeable rock or sediment that holds groundwater and lets it flow, so that water can be stored in it and abstracted from wells and boreholes.

The injection of surplus water, such as treated river water or wastewater, into an aquifer through wells for storage, and its pumping back out through the same wells when it is needed.

A farming system that grows crops, such as cereals, vegetables or oilseeds, on cultivated land rather than raising livestock.

A soil of hot deserts and dry shrublands, low in organic matter, often with layers of calcium carbonate, gypsum or salts because little leaching occurs.

The deliberate addition of water to an aquifer at a rate faster than natural recharge, for example from infiltration basins or injection wells, to replenish groundwater.

The deliberate choice by humans of which individual plants or animals breed, so that desired characteristics become more common over generations; also called selective breeding.

A legally binding agreement signed in 2002 by the members of the Association of Southeast Asian Nations to prevent and monitor land and forest fires and cooperate on the resulting smoke haze.

One of the four broad skills an assessment tests: knowledge and understanding (AO1), application and analysis (AO2), evaluation and synthesis (AO3) and the use of investigative skills (AO4).

The Atlantic part of the thermohaline circulation: warm, salty surface water flows north, cools and sinks in the North Atlantic, and returns south as cold deep water.

The layer of gases held around the Earth by gravity, forming the boundary between the Earth and space and the outer limit of the biosphere.

A planetary boundary process covering the amount of fine particles added to the atmosphere by human activity, which affects climate, rainfall patterns and health.

The large-scale movement of air around the Earth that transfers heat from the equator towards the poles, driven by unequal heating of the Earth's surface.

An organism that synthesises its own organic compounds from inorganic carbon and other elements, using energy from light or from inorganic chemical reactions.

A for-profit company certified by the non-profit B Lab as meeting verified standards of social and environmental performance, accountability and transparency.

The reading and analysis of published sources, theory and models carried out before an investigation, used to explain the environmental issue, justify the research question and support a prediction.

A graph that compares separate categories, such as countries or species, using bars of equal width with gaps between them, whose lengths show the value for each category.

A low dam or barrier with gates built across a river mouth or estuary, used to keep out seawater, store freshwater behind it or control flooding.

An international treaty, in force since 1992, that controls the movement of hazardous wastes between countries, especially from richer to poorer countries, and since 2019 covers plastic waste.

A survey of the environmental and social conditions of a site before a development begins, used to predict and later measure the project’s impacts and to suggest mitigation.

The storage of electricity as chemical energy in rechargeable cells, usually lithium-ion, so that it can be released to the grid very quickly when needed.

A graph that shows how a behaviour, such as smoking or meat eating, changes in a group over time, often annotated with the events or campaigns that may have influenced it.

Reproductive isolation caused by differences in courtship, mating calls, mating times or mate choice, so that populations living in the same area do not interbreed.

A transect along which quadrats are placed, either continuously or at regular intervals, to record abundance along an environmental gradient.

The value people place on passing a resource or ecosystem on intact to future generations.

A systematic distortion of data or results in one direction, arising from how samples are chosen, how questions are asked or how measurements are made.

A legally binding agreement between two states, often used to manage a shared river, lake, border region or migratory population.

The system of naming each species with two words, the genus name with a capital letter followed by the species name in lower case, both written in italics or underlined.

The increase in concentration of a persistent substance in an organism over its lifetime, because it is absorbed faster than it is broken down or excreted.

The capacity of a biologically productive area to generate an ongoing supply of renewable resources and to absorb its wastes; measured in global hectares.

The ethical view that all living organisms have intrinsic value and moral standing, because each pursues its own good through survival and reproduction.

The amount of dissolved oxygen consumed by microorganisms as they decompose the organic matter in a water sample, usually measured in mg per litre over five days at 20 °C.

The capacity of a material to be broken down by living organisms, mainly bacteria and fungi, into simple substances such as water, carbon dioxide, methane and mineral nutrients.

The total variety of life in an area or on Earth, studied at three levels: the diversity of habitats, the diversity of species and the genetic diversity within species.

A region with at least 1,500 endemic vascular plant species that has lost at least 70% of its original natural vegetation, making it both very rich and highly threatened.

A carbon removal method in which crops or trees are burned for energy and the carbon dioxide released is captured and stored underground, giving net removal from the atmosphere.

A fuel produced from recently living organic matter, such as wood, charcoal, crop residues, ethanol from sugar cane or maize, and biodiesel from vegetable oils.

The continuous movement of a chemical element such as carbon or nitrogen between living organisms and the atmosphere, hydrosphere and lithosphere, which keeps the element available to living things.

A planetary boundary process covering human additions of nitrogen and phosphorus to the environment, mainly from fertilisers, which disrupt their natural cycles.

Waste that contains infectious agents or biological material that may harm humans, animals or the environment, such as used needles, dressings, blood and laboratory cultures.

The deliberate use of a living organism, such as a predator, parasite or pathogen, to reduce the population of a pest or invasive species.

The part of the circular economy in which biodegradable materials, such as food and wood, are cascaded into other uses and then returned safely to the soil by composting or anaerobic digestion.

The definition of a species as a group of organisms that can interbreed in nature and produce fertile offspring, and that are reproductively isolated from other such groups.

The increase in concentration of a persistent substance at each successive trophic level of a food chain, because biomass is lost in respiration while the substance is retained.

The mass of organic matter in an organism, population or trophic level, usually measured as dry mass per unit area, such as g m⁻² or kg m⁻².

A group of comparable ecosystems that have developed in similar climatic conditions in different parts of the world and so share similar vegetation structure and adaptations.

A change in where a biome occurs as the climate changes, generally a movement towards the poles and to higher altitudes as the climate warms.

An approach to designing buildings and urban spaces that increases people’s contact with nature, using living walls and roofs, plants, water features, natural light and natural materials.

The use of genetic resources or traditional knowledge from a country or community for commercial gain without their consent or a fair share of the benefits.

The part of the Earth where life exists, including the lower atmosphere, the oceans and fresh waters, and the soil and upper rocks; an ecological system made of individuals, populations, communities and ecosystems.

A sealed research facility in Arizona, USA, built to test a materially closed life-support system; its 1991–1993 mission showed how hard such a system is to keep in balance.

The state of the living part of the Earth system, including the diversity of genes and species and the ability of ecosystems to function; one of the planetary boundaries.

An area recognised by UNESCO that combines biodiversity conservation with sustainable development, divided into a protected core zone, a buffer zone and a transition zone.

A living component of an ecosystem that affects other organisms, such as food supply, predators, competitors, parasites, pathogens and mutualistic partners.

A scale that indirectly measures the quality of an environment, such as a river, from the pollution tolerance, diversity and relative abundance of the organisms living there.

Dark, light-absorbing particles of carbon (soot) from incomplete burning of fossil fuels and biomass, which warm the atmosphere and darken snow and ice when deposited on them.

The use of explosives to stun or kill schools of fish so they can be collected, a destructive and widely illegal method that shatters coral reefs.

A pattern of population change in which rapid growth overshoots the carrying capacity and is followed by a sudden crash, often because resources have been used up.

A biome of high mid-latitudes dominated by coniferous trees, with long cold winters, short mild summers and low productivity limited by temperature and the short growing season.

A garden where living plants are grown, labelled and studied for research, education and conservation, including collections of rare and threatened species.

A fishing method that drags a large cone-shaped net, weighted to stay in contact with the seabed, to catch fish and shellfish living on or near the bottom.

A graph showing the median, the lower and upper quartiles as a box, and the minimum and maximum (or outlier limits) as whiskers, used to compare distributions.

A highly concentrated salt solution, such as the waste water discharged by desalination plants, which is much saltier and denser than seawater.

A fertile, well-drained soil of temperate deciduous forest, with a deep, dark humus-rich A horizon mixed by earthworms over a brown, weakly leached B horizon.

The 1987 report Our Common Future by the UN World Commission on Environment and Development, chaired by Gro Harlem Brundtland, which gave the standard definition of sustainable development.

An area around the core of a protected area where activities compatible with conservation, such as research, education and ecotourism, are allowed, reducing pressure on the core.

The dry mass of soil per unit volume, including its pore spaces, usually in g cm⁻³; high values show compacted soil with little pore space.

Building low banks of earth or lines of stones along the contours of a field to trap run-off water and soil.

A high-capacity bus system with dedicated lanes, stations where passengers pay before boarding and level boarding, giving speeds and reliability close to a tram or metro at lower cost.

Meat from wild animals hunted for food, especially in tropical forests of Africa, Asia and South America, for household use or sale.

A model of the circular economy by the Ellen MacArthur Foundation, showing materials looping back through a technical cycle on one side and a biological cycle on the other.

The unwanted animals caught unintentionally while fishing for a target species, such as juvenile fish, turtles, dolphins and seabirds, which are often discarded dead.

A soil rich in calcium carbonate, usually formed on limestone or chalk parent material, with a neutral to alkaline pH.

The process by which organisms such as corals, molluscs and some plankton build shells or skeletons of calcium carbonate from calcium and carbonate ions dissolved in seawater.

A compound of calcium, carbon and oxygen (CaCO₃) that marine organisms use to build shells and skeletons, and the main component of limestone and chalk.

The measurement of the energy content of a material by burning a dried sample completely, often in a bomb calorimeter, and measuring the heat released.

The breeding of animals of a threatened species in zoos or other managed facilities, often with the aim of increasing numbers and reintroducing them to the wild.

A method of estimating the size of a mobile animal population by capturing, marking and releasing a sample, then recording how many marked individuals appear in a second sample.

The total amount of carbon dioxide that can still be emitted while keeping global warming below a chosen limit, such as 1.5 °C, with a stated probability.

A technology that captures carbon dioxide from power stations or industrial sources and stores it permanently, usually deep underground in rock formations, so that it does not reach the atmosphere.

The biogeochemical cycle by which carbon moves between the atmosphere, organisms, soils, oceans and rocks through processes such as photosynthesis, respiration, decomposition, dissolving and combustion.

The total amount of greenhouse gases produced directly and indirectly by a person, product, organisation or country, expressed in tonnes of CO₂ equivalent.

The movement of production and its emissions from a country with strict climate policies to one with weaker policies, which can cancel out the original emission cuts.

A colourless, odourless, poisonous gas (CO) produced by the incomplete combustion of fuels, which reduces the ability of the blood to carry oxygen.

A state in which the carbon dioxide released by a country, organisation or activity is balanced by an equal amount removed from the atmosphere or offset, giving zero net emissions.

A reduction or removal of greenhouse gas emissions in one place, such as tree planting or avoided deforestation, that is paid for to compensate for emissions released elsewhere.

Any policy that makes emitters pay for each tonne of carbon dioxide they release, either through a carbon tax or through an emissions trading scheme.

The process of capturing carbon dioxide from the atmosphere or from emissions and storing it in solid or liquid form, for example in plant biomass, soils, rocks or underground reservoirs.

A tax charged on each tonne of carbon dioxide emitted, or on the carbon content of fuels, which raises the price of high-carbon activities so that emitters have an incentive to cut emissions.

An animal that feeds mainly on other animals, as a secondary or higher consumer.

The maximum size of a population of a species that an environment can support over a long period, determined by competition for limited resources.

A detailed, real example of a place, event, ecosystem or policy, studied in depth to show how general ideas apply and used as specific evidence in extended answers.

A device in a vehicle exhaust in which metal catalysts convert carbon monoxide, unburned hydrocarbons and nitrogen oxides into carbon dioxide, water and nitrogen.

A clouding of the lens of the eye that blurs vision and can lead to blindness; exposure to ultraviolet radiation, especially UVB, increases the risk.

The catch obtained for a standard amount of fishing effort, such as kilograms per hour of trawling, used as an indirect index of the abundance of a fish stock.

A measure of how many positively charged ions, such as calcium, magnesium and potassium, a soil can hold on the negatively charged surfaces of its clay and humus.

A relationship in which a change in one variable directly produces a change in another, shown by a known mechanism and controlled investigation rather than correlation alone.

The process in all living cells that releases energy from glucose and other organic compounds for cell activities, producing carbon dioxide and water and losing some energy as heat.

The set of natural reactions in which ultraviolet radiation splits oxygen molecules into atoms that form ozone, and ozone is broken down again, keeping stratospheric ozone in a steady state.

An autotroph, usually a bacterium or archaeon, that makes organic compounds using energy released by exothermic inorganic chemical reactions rather than light.

The process by which chemoautotrophs make organic compounds from carbon dioxide using energy from oxidising inorganic substances such as hydrogen sulfide.

A statistical test that compares observed frequencies with those expected if there were no association, used to test for an association between categorical variables.

Stable, non-toxic compounds of carbon, chlorine and fluorine once widely used as refrigerants, aerosol propellants, foam-blowing agents and solvents; they release chlorine that destroys stratospheric ozone.

Building in ways that keep materials in use, by designing buildings for disassembly and reuse, using recovered and recycled materials, and avoiding waste in construction and demolition.

An economic model that aims to decouple economic activity from the consumption of finite resources by eliminating waste and pollution, circulating products and materials, and regenerating nature.

The Convention on International Trade in Endangered Species of Wild Fauna and Flora (1973), a treaty that controls international trade in listed species through three appendices of increasing restriction.

Scientific research in which members of the public take part, often by collecting, recording or analysing data, usually in collaboration with professional scientists.

A group of organisms made up of a common ancestor and all of its descendants, which share characteristics inherited from that ancestor.

A branching diagram showing the probable evolutionary relationships between groups of organisms, in which each branching point represents a common ancestor.

The arrangement of organisms into groups on the basis of their shared characteristics, which allows efficient identification and the prediction of other characteristics.

The finest mineral fraction of soil, with particles smaller than 0.002 mm, made of complex silicate minerals that hold water and positively charged nutrient ions.

The average atmospheric conditions of a place, such as temperature, precipitation, humidity and wind, calculated over a long period, usually about 30 years.

Distress, worry or fear about climate change and its threat to the future, which can affect people's feelings, thoughts and daily functioning, especially among young people.

Long-term changes in the Earth’s climate, including global warming and the wider changes it causes in rainfall, extreme weather, ice cover, sea level and ocean conditions.

Adjustment of human or natural systems to actual or expected climate change, reducing its harmful effects and making the most of any beneficial ones.

Action that reduces the causes of climate change by cutting greenhouse gas emissions, removing greenhouse gases from the atmosphere or reducing the warming process itself.

A graph showing the average monthly temperature of a place as a line and its average monthly precipitation as bars, usually based on about 30 years of data.

An approach to climate change that treats it as an ethical and political issue, asking that responsibility, costs and help be shared fairly given that those least responsible are often most vulnerable.

Legal action in national or international courts to force governments or companies to reduce greenhouse gas emissions, adapt to climate change or pay for climate-related harm.

A computer simulation that uses mathematical equations for the physical, chemical and biological processes of the atmosphere, ocean, land and ice to reproduce past climate and project future climate.

Doubt or denial that climate change is happening, that it is caused mainly by human activity, or that it is serious enough to justify action.

The degree to which a community, country or ecosystem is likely to be harmed by climate change, depending on its exposure, sensitivity and capacity to adapt.

The relatively stable community at the end of a succession, in steady-state equilibrium with the climate and soils of the area.

A survey question with a fixed set of possible answers, such as yes or no, multiple choice or a Likert scale, giving data that can be counted.

A period during which fishing for a species is banned, usually timed to protect it while it spawns or while its young grow.

A system that exchanges energy but not matter with its surroundings; Biosphere 2 and, approximately, the Earth and its global cycles are examples.

A weather modification technique in which particles such as silver iodide or salt are released into clouds to encourage water droplets or ice crystals to form and fall as precipitation.

A unit that expresses the amount of any greenhouse gas as the amount of carbon dioxide that would cause the same warming, so different gases can be added together.

The square of the correlation coefficient, R², giving the proportion of the variation in the dependent variable accounted for by its linear relationship with the independent variable.

The attraction of water molecules to each other through hydrogen bonds, which gives water its high surface tension and lets it be pulled up through plants in columns.

The arrival and establishment of a species in an area where it did not previously live, for example plants spreading onto newly exposed rock.

The burning of a fuel or organic matter in oxygen, a transformation that releases energy as heat and light and returns stored carbon to the atmosphere as carbon dioxide.

Farming in which crops or livestock are produced mainly for sale in markets to earn a profit, rather than for the farmer's own household.

An ancestral species from which two or more later species or groups have evolved, shown as a node on a cladogram.

The principle that all states share responsibility for protecting the global environment, but that richer states, which have caused more damage and have more resources, should take on greater obligations.

A resource that many people can use, where it is difficult to exclude users and each person's use reduces what is left for others, such as ocean fish stocks, groundwater or common grazing land.

A collection of interacting populations of different species living in the same area at the same time.

The squeezing together of soil particles, for example by heavy machinery or trampling, which reduces pore space, aeration, infiltration and root growth.

An interaction in which organisms of the same or different species need the same limited resource, such as food, water, light or space, so that each gets less.

The aerobic decomposition of organic waste, such as food scraps and garden waste, by microorganisms into compost, a stable, humus-rich material used to improve soil.

The transformation of water vapour into liquid water droplets when air cools, which releases latent heat and forms clouds, fog and dew.

The annual meeting of all the countries that are party to the UNFCCC, where climate agreements are negotiated and progress is reviewed.

An ethical approach in which an action is right if it produces the best overall consequences, regardless of the intentions behind it.

The protection, management and sustainable use of species, habitats and ecosystems so that biodiversity and the services it provides are maintained for the present and the future.

A measure of how likely a species is to become extinct in the near future, assessed against standard criteria and expressed as a category such as Vulnerable or Critically Endangered.

An organism that obtains its energy and carbon compounds by feeding on other organisms or their remains, rather than making its own food.

A temperate climate type far from the sea, with a large annual temperature range, cold winters, warm or hot summers and lower precipitation, often peaking in summer.

A survey method that estimates the value of a non-market good by asking people their willingness to pay for it, or to accept compensation for its loss, in a described scenario.

A way of managing forest in which trees are harvested selectively or in small groups, so the canopy and soil are never fully cleared.

Ploughing across a slope along its contours, so that each furrow slows run-off and reduces soil erosion by water.

A factor that could affect the dependent variable and is kept constant, or as constant as possible, so that changes can be attributed to the independent variable.

Choosing survey respondents because they are easy to reach, such as classmates or passers-by at one place and time; quick but likely to be biased.

A broad international agreement, legally binding on the states that ratify it, which sets out general goals and a framework for cooperation on an issue, such as the UNFCCC.

A United Nations treaty opened for signature in 1992 whose objectives are the conservation of biodiversity, the sustainable use of its components and the fair sharing of benefits from genetic resources.

The whitening of corals when heat or other stress causes them to expel the symbiotic algae living in their tissues, leaving them without their main food source and at risk of death.

A shallow, warm-water marine ecosystem built from the calcium carbonate skeletons of corals, with very high productivity and species diversity despite nutrient-poor surrounding water.

The strictly protected central part of a biosphere reserve, where ecosystems are left largely undisturbed and only monitoring and low-impact research are allowed.

The apparent deflection of moving air and water caused by the Earth's rotation: to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

A statistical relationship in which one variable tends to increase (positive) or decrease (negative) as another increases; it does not by itself show causation.

A number from −1 to +1 measuring the strength and direction of a correlation between two variables, with 0 meaning no correlation.

A method of appraising a project or policy by estimating all its costs and benefits in money, including environmental ones where possible, and comparing the totals.

A crop, such as clover, rye or vetch, grown mainly to cover and protect bare soil between main crops rather than to be harvested.

A mineral that is essential to important technologies, such as batteries, magnets and electronics, and whose supply is at risk because production or processing is concentrated in few countries.

The value of a test statistic, read from a table for a chosen significance level and degrees of freedom, that the calculated statistic must exceed for significance.

The IUCN Red List category for species facing an extremely high risk of extinction in the wild, for example with fewer than 50 mature individuals or a decline of 80–90% or more over ten years or three generations.

Growing a different crop on the same field in successive seasons in a planned sequence, often including a legume, to maintain fertility and break pest cycles.

A charge on imported goods according to the carbon dioxide emitted in making them, so that producers in countries without a carbon price cannot undercut those that pay one.

The number of live births per 1,000 people in a population per year, calculated from the total (usually mid-year) population without allowing for its age or sex structure.

The number of deaths per 1,000 people in a population per year, calculated from the total (usually mid-year) population without allowing for its age structure.

All the frozen water of the Earth system, including ice sheets, glaciers, sea ice, snow cover and permafrost.

The planned use of fire by Indigenous people according to traditional knowledge to manage land, such as lighting small, cool fires early in the dry season to prevent large late-season wildfires.

Non-material benefits that people obtain from ecosystems, such as recreation, tourism, beauty, spiritual meaning, education and a sense of place.

The worth of natural capital to the identity, traditions, history and way of life of a group of people, such as a traditional harvest or a landmark central to local customs.

The total amount of a greenhouse gas, usually carbon dioxide, emitted by a country or the world over a long period, typically since the Industrial Revolution.

The use of sodium cyanide sprayed onto coral reefs to stun fish for capture, mostly for the live reef-fish food and aquarium trades, which kills coral and non-target animals.

Photosynthetic bacteria, often called blue-green algae, that can form dense blooms in nutrient-rich water; some species produce toxins.

A toxin produced by cyanobacteria, such as microcystin, which damages the liver, that can poison people and animals that drink or swim in affected water.

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.

Discarded electrical and electronic equipment, such as phones, computers and batteries, which contains valuable metals and hazardous substances such as lead, mercury and brominated flame retardants.

The planet viewed as a single integrated system in which the biosphere, hydrosphere, cryosphere, geosphere, atmosphere and anthroposphere are linked by flows of energy and matter.

The degree to which the Earth’s orbit around the Sun departs from a circle; one of the Milankovitch cycles, varying over periods of about 100,000 and 405,000 years.

A label on a product showing that it meets an independent standard for environmental sustainability, such as seafood from a fishery certified as well managed.

An environmental perspective that gives the natural world pre-eminent importance and intrinsic value, putting ecological processes and all living things ahead of human wants.

The outer boundary of the doughnut economics model, based on the planetary boundaries, beyond which human pressure overshoots the Earth's life-supporting systems.

An approach to economics that treats the economy as a subsystem of society and of the finite biosphere, and aims to keep its scale within the limits of natural systems.

The percentage of the energy received by one trophic level that is passed on to the next; typically 10% or less, but it varies between ecosystems, levels and species.

The area of land and water required to sustainably provide all the resources a population consumes and absorb all the wastes it produces, at its current rates; measured in global hectares.

Reproductive isolation in which populations in the same area use different habitats, food sources or hosts, so they rarely meet to mate.

The situation in which a population's ecological footprint exceeds the biocapacity available to it, so that natural capital is depleted and wastes accumulate.

A diagram of stacked horizontal bars, one per trophic level, whose widths show the relative numbers, biomass or energy at each level.

The process of helping a degraded, damaged or destroyed ecosystem recover, for example by replanting native species, removing invasive species or restoring natural water flows.

A holistic approach to planning that treats the urban system as an ecosystem, designing land use, buildings and infrastructure around the relationships between people, other organisms and the abiotic environment.

The growing integration of national economies through international trade, investment and supply chains, which increases supply of resources but also interdependence between countries.

The change in the total market value of the goods and services produced in a country over a period, usually measured as the annual percentage change in GDP.

The maintenance of economic structures and systems that support the production and consumption of goods and services to meet human needs into the future.

The worth of natural capital that can be traded or measured in money, such as the market price of timber, fish, minerals or farmland.

A shortage of water caused by a lack of investment in storage, treatment and distribution, or by a lack of human capacity, even though enough freshwater exists naturally.

The study of how individuals and societies produce, distribute and consume goods and services, and how they allocate limited resources between competing uses.

A protected area surrounded by a pest-exclusion fence, inside which introduced predators are removed so that native species can be reintroduced and recover.

A community of interdependent organisms and the physical environment with which it interacts.

A change in which an ecosystem loses its defining species, structure or functions and shifts to a different, usually less valuable state from which recovery is slow or impossible.

An organism that creates, modifies or maintains habitat by changing the physical environment, such as beavers building dams or elephants pushing over trees.

The extent to which an ecosystem keeps its natural structure, species composition and processes, such as nutrient cycling, so that it can function and recover from disturbance.

The benefits that ecosystems provide to people and other living things, grouped as provisioning, regulating, cultural and supporting services, such as food, flood control, recreation and nutrient cycling.

A transition zone between two communities or biomes, where species from both occur and the community changes along an environmental gradient.

Responsible travel to natural areas that conserves the environment, sustains the well-being of local people and involves education, with income that can help fund protection.

The changes in conditions and species at the boundary between two habitats, such as more light, wind, predators and invasive species at the edge of a forest reserve than in its interior.

Liquid waste discharged into the environment from a pipe or outfall, such as treated or untreated sewage or industrial wastewater.

The removal from the gut of undigested food that was never absorbed into the body, as faeces.

The warm phase of ENSO, in which the Walker circulation weakens or reverses, warm water spreads east across the tropical Pacific and upwelling off western South America decreases.

The irregular fluctuation in winds and sea-surface temperatures across the tropical Pacific Ocean between El Niño, neutral and La Niña states, which affects weather in many parts of the world.

The full range of electromagnetic radiation, from long-wavelength radio waves through microwaves, infrared, visible light and ultraviolet to short-wavelength X-rays and gamma rays.

A characteristic of a system that arises from the interactions between its components and is not shown by any component on its own.

The number of people leaving an area to live elsewhere, per 1,000 people of the population they leave per year.

A plausible description of how future greenhouse gas and aerosol emissions could develop, based on assumptions about population, economy, technology and policy, used as an input to climate models.

A scheme in which a government caps total emissions, issues permits up to the cap and lets emitters buy and sell them, so that emissions are cut where it is cheapest.

The IUCN Red List category for species facing a very high risk of extinction in the wild, between Vulnerable and Critically Endangered.

A species found naturally in only one place, such as a single island, country or mountain range, and nowhere else in the world.

A chemical that interferes with the production or action of hormones in an organism, disrupting growth, development or reproduction, often at very low concentrations.

A lake in a basin with no outlet to the sea, which loses water only by evaporation and seepage, so dissolved salts build up in it.

Reducing energy consumption by changing behaviour so that less of an energy service is used, such as switching off lights, turning heating down or travelling less.

Using technology to obtain the same energy service, such as light, warmth or transport, from less energy input, for example with LED lighting, insulation or efficient engines.

The one-way movement of energy through an ecosystem, entering mainly as sunlight, passing between trophic levels as chemical energy in food, and leaving as heat.

A systems diagram showing energy entering, passing between and leaving trophic levels, with arrows whose widths are often drawn in proportion to the size of each flow.

The combination of primary energy sources used to meet the energy demand of a country or region, usually expressed as the percentage supplied by each source.

The uninterrupted availability of energy sources at an affordable price; reliable access by a society to enough affordable energy to meet its needs now and in the future.

The capture of energy produced at one time, as chemical, gravitational potential or thermal energy, so that it can be released as electricity or heat later.

The strengthening of the natural greenhouse effect by greenhouse gases added to the atmosphere by human activities, such as burning fossil fuels and farming, which causes global warming.

The digestion of plant material by microorganisms in the gut of ruminant animals, which releases methane that the animals breathe out or belch.

A measure of the disorder of a system and of how spread out its energy is; it increases in every energy transformation as energy is degraded to heat.

The attempt to attach economic values to natural resources, ecosystem services and their depletion, and to include these values in the accounts of businesses or nations.

A person who campaigns publicly, through protest, advocacy, writing or direct action, to change attitudes, behaviour or policy on an environmental issue.

A check made during or after a development project that compares its actual environmental impacts with those predicted and tests whether mitigation and legal conditions are being met.

The inclusion of environmental rights and duties in a country's constitution, such as a right to a healthy environment or rights for nature, so that they rank above ordinary laws.

A branch of economics that applies economic principles to environmental issues, treating environmental damage as a cost to be measured and corrected within the existing market economy.

The branch of ethics that studies the moral relationship between humans and the natural environment, including the moral status of non-human and non-living entities.

The quantity, timing and quality of water flow that must be left in a river, wetland or estuary to sustain its ecosystems and the people who depend on them.

A gradual change in one or more abiotic factors, such as temperature, exposure or soil moisture, across a distance in space.

A process carried out before a development project is approved that identifies and predicts its environmental, social and economic impacts, proposes mitigation, and is followed by monitoring and audits.

The right of all people to live in a pollution-free environment and to have equitable access to natural resources, regardless of race, gender, socio-economic status or nationality.

A hypothesis that environmental degradation rises as income per person grows and then falls once a country is rich enough, giving an inverted U-shaped curve.

The body of rules governing how people use and affect natural resources and the environment, covering resources, pollution, biodiversity and development, with the aim of improving social and ecological sustainability.

The movement of people, temporarily or permanently, within or across borders, mainly because sudden or gradual changes in the environment harm their lives or living conditions.

The broad social and political movement of individuals, groups and organisations that works to protect the natural environment and change human behaviour, policy and law towards it.

The use and management of natural resources in a way that allows resources to be replaced and ecosystems to recover and regenerate, avoiding depletion, pollution and biodiversity loss.

A model of a person's or society's environmental perspective as a system, showing the inputs that shape it (such as education, media and worldviews) and the outputs that result (judgements, choices and actions).

A state of balance in a system, in which opposing flows or processes cancel out so that there is no overall change in the system.

The long-term rise in global mean surface temperature once the climate has fully adjusted to a doubling of atmospheric carbon dioxide; the IPCC's best estimate is 3 °C.

Fairness in the distribution of resources, opportunities, costs and benefits, so that no group is systematically disadvantaged; equitable does not necessarily mean equal.

Lines drawn above and below a plotted value, such as a mean, showing its variability or uncertainty, for example one standard deviation either side.

A farmed aquatic animal that has escaped from its cage or pond into the wild, where it may compete with, breed with or spread disease to wild populations.

A structured set of moral principles used to judge whether actions or decisions are right or wrong, such as virtue, consequentialist or rights-based ethics.

The branch of philosophy concerned with moral principles, that is, with which behaviours are right or wrong and how people ought to act.

The enrichment of lakes, estuaries and coastal waters with mineral nutrients, especially nitrates and phosphates, often causing excessive phytoplankton growth and oxygen depletion.

The transformation of liquid water into water vapour, using heat energy mainly from solar radiation; the main flow from the oceans to the atmosphere.

The combined flow of water vapour to the atmosphere by evaporation from soil and water surfaces and by transpiration from plants.

The cumulative change in the heritable characteristics of a population or species over many generations.

Conservation of species outside their natural habitats, for example in zoos, botanic gardens, seed banks and captive-breeding programmes.

A zone of sea extending up to 200 nautical miles (370 km) from a country's coast, in which that country has sovereign rights over fishing and other natural resources under UNCLOS.

The value people place on simply knowing that a species, ecosystem or place exists, even if they never use or visit it.

Growth of a population by a constant proportion in each time period, so that numbers double at regular intervals and the growth curve becomes ever steeper.

The phase of an S-shaped growth curve in which a population grows rapidly and at an increasing rate because resources are plentiful.

A policy approach that makes manufacturers responsible, financially or physically, for collecting and recycling or disposing of their products at the end of their life.

Farming with low inputs of capital, labour or materials per unit area, usually spread over large areas and giving relatively low yields per hectare.

A cost or benefit of producing or consuming a good that falls on a third party not involved in the transaction, who is neither compensated nor charged for it.

The IUCN Red List category for species that survive only in captivity, in cultivation or as populations established outside their natural range.

The permanent disappearance of a species, when its last individual dies.

The number of species that become extinct in a given period, often expressed as extinctions per million species per year and compared with the natural background rate.

A weather event that is rare at a particular place and time of year, such as a heatwave, intense rainfall, drought or tropical cyclone, far outside the usual range of conditions.

A process in succession in which one species changes the conditions, for example by adding nitrogen or organic matter to the soil, in a way that helps other species to establish.

A measure of water availability based on renewable freshwater per person per year: below 1,700 m³ indicates water stress, below 1,000 m³ scarcity and below 500 m³ absolute scarcity.

The practice of leaving farmland uncropped for one or more seasons so that soil nutrients, organic matter and structure can recover.

The services, information and means, such as contraception, that allow people to decide whether, when and how many children to have.

An extreme and widespread lack of food in a region, causing large numbers of deaths from starvation and disease, resulting from failures of food availability and access.

The return of part of the output of a process to affect the same process, so that a change in a system either reduces itself (negative) or increases itself (positive).

A field method of estimating soil texture by moistening and rubbing a small sample between the fingers to judge grittiness, smoothness and stickiness.

The cell of atmospheric circulation between about 30° and 60° latitude, in which air sinks in the subtropics, moves poleward at the surface and rises near 60°.

A substance added to soil or plants to supply nutrients, especially nitrogen, phosphorus and potassium, and so increase growth and yield.

Money, credit and other financial assets that can be used to buy or invest in other forms of capital.

The physical law that energy can be transformed from one form to another but cannot be created or destroyed, so the total energy entering a system equals the total leaving or stored.

A population of one fish species in a defined area that breeds largely within itself and is assessed and managed as a single unit.

An activity or industry that catches or farms a particular aquatic species in a particular area, together with the people, vessels and methods involved.

A dramatic and lasting decrease in a fish stock to a level at which it can no longer support a commercial fishery and cannot recover quickly, even when fishing stops.

The amount of fishing carried out over a period, measured for example as the number of vessels, days at sea, hours of trawling or hooks set.

A legal limit on the amount of a species, usually in tonnes, that a country, fleet or vessel may catch in a period, often set from a total allowable catch.

A charismatic species, such as the giant panda or the tiger, used to raise public awareness and funding for conservation of its habitat and of the many less-known species that share it.

A sudden flood that rises within minutes to a few hours of intense rainfall, usually because surface run-off reaches rivers or drains faster than they can carry it.

A structure such as a levee, embankment, sea wall or storm surge barrier built to stop river or sea water from flooding land.

The movement of energy or matter between storages, or into or out of a system, measured as a rate and drawn as an arrow in systems diagrams.

A sequence of organisms in which each feeds on the one before, showing the path of energy and biomass from a producer to higher consumers.

The distance food travels from where it is produced to where it is eaten, used as a rough indicator of the environmental impact of food transport.

A situation in which all people at all times have physical and economic access to enough safe and nutritious food to meet their dietary needs for an active, healthy life.

Food fit to eat that is discarded at the retail, food-service or household stage; food lost earlier, during harvest, storage, processing and transport, is called food loss.

A network of interconnected food chains in an ecosystem, showing all the feeding relationships, including species that feed at more than one trophic level.

The large-scale death of trees across a forest, often from drought, heat, fire or pests, which can turn the forest from a carbon store into a carbon source and shift it towards savanna.

An approach to conservation that creates protected areas by excluding local and Indigenous people, removing settlements and banning their use of land and resources.

A carbon-rich fuel such as coal, oil or natural gas, formed over millions of years from the partly decomposed remains of ancient organisms buried in sediments.

The total collection of preserved remains and traces of past organisms found in rocks, in the order in which they were laid down, used to reconstruct the history of life.

A forest restoration method that plants a mix of fast-growing native trees chosen to close the canopy quickly and attract seed-dispersing animals, which then bring in other species.

A market in which prices and quantities are set by the voluntary exchange between buyers and sellers, with little or no government control.

An atom or molecule with an unpaired electron, such as a chlorine atom released from a CFC, which makes it highly reactive.

A person or country that enjoys the benefits of a shared resource or collective action without paying its share of the cost, such as a country that lets others cut emissions.

Water with a low concentration of dissolved salts, usually below about 1 g per litre, found in rivers, lakes, groundwater, ice and the atmosphere, and usable for drinking and irrigation.

A planetary boundary process covering human disturbance of the water cycle, measured by changes in river flows (blue water) and in soil moisture (green water).

A device that converts the chemical energy of a fuel, usually hydrogen, directly into electricity by combining it with oxygen, producing water and heat as by-products.

The full range of conditions and resources in which a species could survive and reproduce if there were no limiting biotic factors such as competition or predation.

The model, proposed by James Lovelock and developed with Lynn Margulis, of the Earth as a single self-regulating system in which life and its surroundings interact through feedback to keep conditions suitable for life.

An area at the centre of an oceanic gyre where floating debris, mostly plastic fragments and lost fishing gear, accumulates at unusually high concentrations.

A genetic technique that makes a modification inherited at a higher rate than normal, so that it spreads through a wild population, proposed for reducing malaria-carrying mosquitoes or invasive predators.

The range of different genes and alleles within one species or population, which allows individuals to differ in heritable characteristics.

The direct alteration of an organism's DNA using biotechnology, for example by inserting a gene from another species, to give it a new characteristic.

A group of closely related species that share many characteristics; the first part of a binomial name, written with a capital letter.

Deliberate, large-scale intervention in the Earth's climate system to counter global warming, either by reflecting sunlight away from the Earth or by removing carbon dioxide from the atmosphere.

The separation of populations by a physical barrier such as a river, sea, mountain range or habitat gap, which stops them interbreeding.

A subdivision of a geological period, lasting from thousands to tens of millions of years, whose boundaries are defined by changes in rock strata and fossils.

The system that divides Earth's 4.5-billion-year history into eons, eras, periods and epochs, with boundaries marked by major geological and biological events in the rock record.

The solid, non-living part of the Earth system, made of rocks, minerals, sediments and soil, including the lithosphere.

Heat from the Earth’s interior, brought to the surface as hot water or steam and used to generate electricity or to heat buildings directly.

The continued catching and killing of marine animals by fishing gear, such as nets, lines and traps, that has been lost or abandoned at sea.

A cold interval within an ice age, lasting tens of thousands of years, when ice sheets expand, sea level falls and atmospheric carbon dioxide is low, about 180–200 ppm in recent cycles.

The balance between the solar energy Earth absorbs and the energy it returns to space as reflected sunlight and emitted infrared radiation, which sets the planet's mean temperature.

A unit of area equal to one hectare of land or water with the world-average biological productivity, used to measure ecological footprints and biocapacity.

The increase in the mean global surface temperature of the Earth, caused mainly by the enhanced greenhouse effect; one part of climate change.

A measure of how much warming a given mass of a gas causes over a set period, usually 100 years, compared with the same mass of carbon dioxide, which has a value of 1.

The informal name for a Global Boundary Stratotype Section and Point: an agreed point in a rock or sediment sequence at one site that marks the start of a geological time unit.

The steepness of a line on a graph, calculated as the change in the vertical value divided by the change in the horizontal value; on a time graph it gives the rate of change.

The period beginning about 2.4 billion years ago when oxygen produced by photosynthesising cyanobacteria first built up in the Earth’s atmosphere and shallow oceans.

An approach to building design and construction that minimises harm to health and the environment over a building’s whole life through eco-friendly materials, low energy and water use and safe practices.

A building designed, built and operated to reduce its use of energy, water and materials and its harmful effects on health and the environment over its whole life.

A measure of economic output that subtracts the monetary value of environmental costs, such as resource depletion and pollution damage, from gross domestic product.

A crop, often a legume, that is grown and then ploughed back into the soil to add organic matter and nutrients instead of being harvested.

The rapid rise in cereal yields in many low- and middle-income countries from the 1950s and 1960s, based on high-yielding varieties, irrigation, synthetic fertilizers and pesticides.

A roof partly or completely covered with soil and vegetation, which insulates the building, slows rainwater run-off, cools the surrounding air and provides habitat.

Land in an urban area partly or completely covered by grass, trees, shrubs or other vegetation, such as parks, gardens, playing fields and river corridors.

A tax on an activity or product that harms the environment, such as carbon, landfill or plastic bags, designed to discourage the harm and make the polluter pay.

A vertical surface of a building covered with plants rooted in soil or a growing medium fixed to the wall, which insulates and cools the building, traps dust and provides habitat.

The natural process by which greenhouse gases absorb infrared radiation emitted by the Earth’s surface and re-emit it in all directions, keeping the surface about 33 °C warmer than it would otherwise be.

A gas in the atmosphere, such as water vapour, carbon dioxide, methane or nitrous oxide, that absorbs and re-emits infrared radiation emitted by the Earth’s surface, so less escapes directly to space.

The use of marketing, advertising or public relations to make a company, product or policy appear more environmentally friendly than it really is, instead of changing harmful practices.

Lightly used wastewater from showers, baths, washbasins and washing machines, which can be filtered and reused for flushing toilets or watering gardens.

The total monetary value of all final goods and services produced and sold in a country in a given period, usually one year.

An index of collective well-being used by the government of Bhutan as an alternative to GDP, covering domains such as health, education, culture, good governance and ecological resilience.

The total rate at which producers fix energy or carbon by photosynthesis or chemosynthesis per unit area per unit time, before respiratory losses.

The total gain in biomass or energy by an organism or trophic level per unit area per unit time, before any is lost in respiration.

The rate at which consumers absorb energy or biomass from food, equal to food ingested minus faecal losses, per unit area per unit time.

Water held underground in the pores and cracks of soil and rock below the water table, where the ground is fully saturated.

The slow transfer of water through saturated rock or sediment, which feeds springs, rivers, lakes and the sea.

The accumulated droppings of seabirds or bats, rich in nitrogen and phosphate, which add nutrients to soils and have been mined as fertiliser.

The industrial process that combines nitrogen from the air with hydrogen, at high temperature and pressure over an iron catalyst, to make ammonia, mainly for fertilisers.

The location in which a community, species, population or organism lives, including its physical features and the type of ecosystem that meets its needs.

The range of different habitats, such as forest, wetland and grassland, found in an area; often treated as the variety of ecosystems or communities present.

The division of a large, continuous habitat into smaller, isolated patches separated by roads, farmland or other land uses, which reduces population sizes and increases edge effects.

The conversion of a natural habitat to another land use, such as farmland, plantations, mines or cities, so that it can no longer support the species that lived there; the largest single cause of biodiversity loss on land.

An approach to conservation that protects species by conserving their natural environment, usually in situ in protected areas, so that whole communities and ecosystem processes are kept.

The cell of atmospheric circulation between the equator and about 30° latitude, in which warm air rises at the equator, moves poleward at height and sinks in the subtropics.

The time taken for half of the amount of a substance to break down or decay, such as half of the radioactive nuclei in a sample or half of a pollutant in the environment.

A layer in a water body in which salinity changes rapidly with depth, separating fresher surface water from saltier, denser water below.

One of a group of reactive elements (fluorine, chlorine, bromine and iodine); chlorine and bromine released from ozone-depleting substances destroy stratospheric ozone.

A bloom of algae, cyanobacteria or other phytoplankton that harms people, animals or ecosystems, especially by producing toxins or by clogging the gills of fish.

A method for estimating primary productivity on land by harvesting, drying and weighing the plant biomass in sample plots at intervals and calculating the gain per unit area per unit time.

An animal that feeds on living plants or algae, so it is a primary consumer.

An interaction in which an animal feeds on plants or algae, benefiting the herbivore and harming the plant.

An organism that cannot make its own organic compounds and obtains them by feeding on other organisms or their remains.

The parts of the ocean beyond any country's exclusive economic zone, open to all states and governed only by international agreements and regional fisheries bodies.

The UN agreement on marine biodiversity of areas beyond national jurisdiction, adopted in 2023 and in force from January 2026, which allows marine protected areas and impact assessments on the high seas.

A crop variety bred to produce a high yield of grain per hectare when supplied with enough water, fertilizer and pest control.

Testing a climate model by running it over a past period with the known inputs and comparing its output with the climate that was actually observed.

A graph of the frequency of continuous data grouped into classes, drawn as touching bars whose areas are proportional to the number of values in each class.

A way of studying a situation by looking at the whole system and the interactions between its parts, rather than at each part separately.

The geological epoch of roughly the last 12,000 years, a period of unusually stable climate in which agriculture, cities and human civilisations developed.

A biome with very low and unreliable precipitation, usually under about 250 mm a year, and high daytime temperatures, in which water is the main limiting factor.

The knowledge, skills, health and abilities of people that allow them to produce goods and services and earn income.

The maximum number of people an area or the Earth can support sustainably, given its resources, technology and level of consumption; difficult to estimate and changing over time.

Human faeces and urine composted at high temperature for long enough to kill pathogens, then used as an organic fertilizer.

Dark brown or black, partly decomposed organic matter in soil with a loose, crumbly texture, which holds water and nutrients and binds particles together.

Compounds of hydrogen, chlorine, fluorine and carbon used as transitional replacements for CFCs; they release less chlorine into the stratosphere but still deplete ozone and are being phased out.

Electricity generated when water stored at a height, usually behind a dam, flows down through turbines that drive generators.

Compounds of hydrogen, fluorine and carbon that replaced CFCs and HCFCs in refrigeration, air conditioning, aerosols and foams; they do not deplete ozone but are powerful greenhouse gases.

A weak attraction between a slightly positive hydrogen atom of one molecule and a slightly negative atom, such as oxygen, of another molecule.

The continuous circulation of water between the oceans, atmosphere, land and living things, driven by solar radiation and gravity, through stores linked by transfers and transformations.

A method of growing plants without soil, with their roots in a solution of water and dissolved mineral nutrients, often in greenhouses or indoor farms.

All the liquid water on and near the Earth's surface, including oceans, lakes, rivers and groundwater, considered as one part of the Earth system.

An opening in the sea floor, usually at a spreading ridge, from which hot, mineral-rich water emerges, supporting food webs based on chemosynthetic bacteria.

A testable prediction of the outcome of an investigation, stating the expected relationship or difference between variables and supported by a scientific reason.

A condition in which dissolved oxygen in water is too low to support most animal life, commonly defined as 2 mg per litre or less.

The property of a system in which the path of recovery differs from the path of collapse, so a pressure must be reduced well below the level that caused a regime shift before the original state returns.

A model that expresses human environmental impact (I) as the product of population size (P), affluence or consumption per person (A) and the impact of the technology used per unit of consumption (T).

A cylinder of ice drilled from an ice sheet or glacier whose layers and trapped air bubbles record past atmospheric composition and temperature, in Antarctica going back about 800,000 years.

A mass of glacial land ice larger than 50,000 km², such as the Greenland and Antarctic ice sheets, which together hold enough water to raise sea level by tens of metres.

A positive feedback in which warming melts reflective snow and ice, exposing darker ocean or land that absorbs more solar radiation, which causes further warming and melting.

The unlawful capture, transport and sale of wild animals, plants or their parts, for pets, food, medicine, ornaments or collections, often across national borders.

Fishing that breaks national or international rules, is not reported or is misreported to the authorities, or takes place where no management rules apply, undermining the management of fish stocks.

The number of people moving into an area to live, per 1,000 people of the receiving population per year.

A surface such as concrete, asphalt or a roof that water cannot pass through, so rain becomes surface run-off instead of infiltrating.

The development of male sex organs in female marine snails, such as dog whelks, caused by exposure to endocrine disruptors such as tributyltin.

Conservation of species in their natural habitats, for example in national parks, nature reserves and sanctuaries, so that their ecological relationships and processes are kept.

The burning of waste at high temperatures in a controlled furnace, which greatly reduces its volume and leaves ash, flue gases and heat.

The variable that an investigator changes, chooses or compares in order to see its effect on another variable; plotted on the x-axis of a graph.

A species whose presence, absence or abundance shows a particular environmental condition, such as a level of pollution, because it is sensitive to or tolerant of that condition.

The collective and individual rights of Indigenous peoples, including rights to their lands, territories, resources and culture, and to give or withhold free, prior and informed consent to projects affecting them.

The internally assessed component of ESS, in which each student designs and carries out an investigation of their own environmental research question and presents it as a written report of up to 3,000 words.

The shift from hand production to machine-based manufacturing powered by coal, which began in Britain in the late 18th century and marks the start of large-scale human emissions of carbon dioxide.

The number of deaths of children under one year of age per 1,000 live births in a year.

The transfer of water from the ground surface into the soil.

Agreement to take part in an investigation given by a person who has been told its purpose, what is involved, how their data will be used and that they may withdraw.

Electromagnetic radiation with wavelengths longer than visible light; the Earth’s warmed surface emits long-wave infrared, part of which is absorbed and re-emitted by greenhouse gases.

A flow of energy or matter that crosses the boundary into a system, such as sunlight or rainfall entering an ecosystem.

A plant, such as a pitcher plant or sundew, that traps and digests insects to obtain nitrogen and other nutrients missing from the waterlogged, nutrient-poor soils where it grows.

The amount of incoming solar radiation reaching a given area of the Earth's surface, which varies with latitude, season, time of day and cloud cover.

The value something has as a means to an end, because it is useful to people, such as a forest valued for timber, water supply or tourism income.

A form of aquaculture that farms species from different trophic levels together, so that wastes from fed species such as fish become food or nutrients for shellfish, deposit feeders and seaweeds.

Farming with high inputs of capital, labour, energy, fertilizer or other materials per unit area, producing high yields per hectare.

The temporary storage of precipitation on leaves, stems and other surfaces before it evaporates or drips and flows to the ground.

Fairness between generations, so that people living now do not use resources or cause damage in ways that leave future generations with fewer opportunities.

A warmer interval between glacial periods, usually lasting about 10,000–30,000 years, when ice sheets retreat and atmospheric carbon dioxide is higher; the Holocene is the present interglacial.

An organisation whose members are national governments, set up by treaty to cooperate on shared issues, such as the United Nations Environment Programme (UNEP).

The United Nations body, set up in 1988, that assesses the published science on climate change and reports on its causes, impacts and the options for mitigation and adaptation.

The property of an energy source whose output varies with conditions that cannot be controlled, such as wind speed or sunlight, so that it is not always available when needed.

The principal court of the United Nations, in The Hague, which settles legal disputes between states and gives advisory opinions on questions of international law, including environmental law.

The body of treaties, customary rules and court decisions between states that governs transboundary pollution, shared resources and global environmental problems, binding states that consent to it.

An international court in Hamburg with 21 judges, created by the UN Convention on the Law of the Sea, which settles disputes over fishing, marine pollution and maritime boundaries and gives advisory opinions.

An international organisation of governments, government agencies and non-governmental organisations, founded in 1948, that assesses the conservation status of species and publishes the IUCN Red List.

The international body set up under the 1946 International Convention for the Regulation of Whaling that sets catch limits and has kept a moratorium on commercial whaling since 1986.

The difference between the upper and lower quartiles of a data set, measuring the spread of its middle half and little affected by extreme values.

Competition between individuals of different species for the same limited resource.

The belt of low pressure near the equator where the trade winds of the two hemispheres meet and warm, moist air rises, bringing heavy convectional rain; it moves north and south with the seasons.

Competition between individuals of the same species for the same limited resource.

The value something has in and for itself, regardless of whether it is useful to people, as when a species is considered worth protecting simply because it exists.

An alien species that establishes itself, spreads rapidly and harms native biodiversity, ecosystems, the economy or human health, through competition, predation, disease or poisoning.

The artificial supply of water to farmland from rivers, reservoirs or groundwater to grow crops where or when rainfall alone is not enough.

A theoretical system that exchanges neither energy nor matter with its surroundings; no true example exists on Earth.

A global assessment of the extinction risk of species, published by the IUCN, that places each species in a category from Least Concern to Extinct using standard quantitative criteria.

A growth curve in which population size rises ever more steeply with time, showing exponential growth with no limiting factors.

A species that reproduces late and produces few large offspring with much parental care and a high chance of survival, adapted to stable environments near carrying capacity.

The Māori concept and practice of guardianship of the natural environment, carried out by kaitiaki (guardians) responsible for the long-term well-being of land, water and living things.

A graph of the concentration of carbon dioxide in the atmosphere measured continuously at Mauna Loa, Hawaii, since 1958, showing a steady rise with a yearly seasonal oscillation.

A site identified, using a global standard published by the IUCN in 2016, as contributing significantly to the global persistence of biodiversity, for example by holding much of a threatened species' population.

A species that has a disproportionately large effect on the structure of its community relative to its abundance, so that its removal can cause the community to change greatly or collapse.

A method of sampling stream invertebrates by disturbing the stream bed with the feet for a set time just upstream of a net held against the current.

The 2016 amendment to the Montreal Protocol that commits countries to cut the production and use of hydrofluorocarbons by 80–85% over the following decades because they are powerful greenhouse gases.

A graph that shows how the abundance of each species changes along a transect, with the width of each band proportional to its abundance at each point.

A plan adopted under the Convention on Biological Diversity in December 2022, with four goals for 2050 and 23 targets for 2030, including conserving 30% of land and sea.

An international agreement adopted in 1997 under the UNFCCC that set legally binding emissions targets for developed countries for 2008–2012.

The cool phase of ENSO, in which the Walker circulation and the trade winds strengthen, cold upwelling off western South America increases and the western Pacific becomes wetter.

The first phase of an S-shaped growth curve, in which a population grows slowly because there are few individuals to reproduce.

The seasonal mixing of a whole lake from top to bottom when surface and deep water reach the same temperature and density, usually in spring and autumn.

Aldo Leopold's ecocentric principle that an action is right when it tends to preserve the integrity, stability and beauty of the biotic community, and wrong when it tends otherwise.

The legal or customary rights of individuals or communities to own, use, control and pass on land and its resources.

Planning rules that control what land may be used for in each area, for example banning new homes on floodplains or in zones at risk of storm surges.

A planetary boundary process covering the conversion of forests, grasslands and wetlands to farmland, settlements and other uses, measured by remaining forest cover.

A site where waste is buried in the ground; a sanitary landfill is engineered with a liner, daily cover and systems to collect leachate and landfill gas.

The rate at which air temperature falls with increasing altitude in the troposphere: about 1 °C per 100 m for rising dry air and on average about 0.65 °C per 100 m in the real atmosphere.

Energy absorbed or released when a substance changes state without a change in temperature, such as the heat taken in by evaporation and given out by condensation.

The angular distance of a place north or south of the equator, measured in degrees from the centre of the Earth, from 0° at the equator to 90° at the poles.

A rule that governs human behaviour, made and enforced by a social or governmental authority, so that breaking it can bring a penalty such as a fine, an order to repair damage or prison.

The liquid formed when water percolates through waste, carrying dissolved substances such as organic compounds, ammonia and heavy metals that can pollute soil, groundwater and rivers.

The removal of dissolved minerals and nutrients from soil as water percolates downwards through it, carrying them to lower horizons or groundwater.

The layer of fallen leaves, twigs, bark and other dead plant parts lying on the soil surface, the main input of dead organic matter to most soils.

The IUCN Red List category for species that have been assessed and do not qualify for a higher-risk category, usually because they are widespread and abundant.

The status of being recognised by law as able to hold rights and duties and to sue or be sued, given to companies and increasingly to natural entities such as rivers and forests.

A plant of the pea and bean family, such as clover, beans, peas, lentils and soya, whose root nodules hold nitrogen-fixing bacteria.

Land sown with grass, often mixed with clover and herbs, for a few years as part of a rotation, grazed or cut, then ploughed for arable crops.

The sequence of stages an organism passes through from the start of its life to reproduction and death, including its timing and lifespan.

The average number of years a person can expect to live, usually measured from birth, if the death rates at each age at the time stay the same throughout their life.

A method for measuring aquatic primary productivity by comparing the change in dissolved oxygen in clear and darkened bottles of water incubated together for a set time.

A rating scale on which respondents show how strongly they agree or disagree with a statement, usually with five or seven points from strongly disagree to strongly agree.

A sedimentary rock made mostly of calcium carbonate, often from the shells and skeletons of marine organisms; the largest carbon store on Earth, holding carbon for hundreds of millions of years.

The addition of crushed limestone or other calcium compounds to acidic soil to raise its pH and make nutrients more available to plants.

The environmental factor, abiotic or biotic, that is in shortest supply relative to need and therefore restricts the growth, abundance or distribution of a population.

A method of estimating the size of a population of mobile animals from capture-mark-release-recapture data, calculated as (M × N) ÷ R.

A graph that plots values of a dependent variable against a continuous independent variable, usually time, and joins the points with lines to show change and trends.

A straight line or smooth curve drawn through a set of plotted points so that it represents the general trend, with the points spread roughly evenly on either side of it.

A transect along which every organism touching the line is recorded at set intervals.

An economic model in which raw materials are extracted, made into products, used and then discarded as waste; often summarised as take, make, waste.

Natural gas, mainly methane, cooled to a liquid at about −162 °C so that it can be shipped in tankers and turned back into gas at an import terminal.

The rigid outer layer of the solid Earth, made of the crust and the uppermost mantle, which forms the base of soils and landforms.