38 of the ESS glossary’s terms, each with the part of the syllabus where you first meet it.
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.