30 of the ESS glossary’s terms, each with the part of the syllabus where you first meet it.
The organic layer at the top of a soil profile, made of leaf litter and humus at different stages of decomposition, above the mineral soil.
The angle of tilt of the Earth’s axis, which varies between about 22.1° and 24.5° over a cycle of about 41,000 years; greater tilt gives stronger seasons.
The ongoing decrease in the pH of seawater caused by the oceans absorbing carbon dioxide from the atmosphere, which also lowers the concentration of carbonate ions.
A continuous, directed movement of seawater, driven by wind, the Earth's rotation and differences in water density, that transfers heat around the globe.
A geoengineering method that adds nutrients, usually iron, to parts of the ocean where they limit phytoplankton growth, so that the extra phytoplankton absorb carbon dioxide.
A large, roughly circular system of ocean surface currents driven by prevailing winds and the Earth’s rotation, which can concentrate floating debris at its centre.
A measure of ENSO used by NOAA: the three-month running mean of the sea-surface temperature anomaly in the central equatorial Pacific (the Niño 3.4 region).
The release of crude oil or refined fuel into the environment, especially the sea, from tankers, offshore rigs, pipelines or storage facilities.
An animal that feeds on both plants and animals, so it can occupy more than one trophic level.
The Organization of the Petroleum Exporting Countries, an intergovernmental group of oil-exporting states founded in 1960 that coordinates its members’ oil production and policies.
The disposal of waste on land without engineering, cover or lining, so that it is exposed to rain, wind, animals and people and is often burned in the open.
A survey question that respondents answer in their own words, giving rich qualitative data that are harder to count and compare.
A system that exchanges both energy and matter with its surroundings across its boundary; almost all natural ecosystems are open systems.
A level at which decisions and actions for sustainability are taken: individual, business, community, city, country or global.
The value of keeping a resource available for a possible future use, such as a plant that may one day yield a medicine.
A carbon compound made by living organisms, such as glucose, proteins and fats, that stores chemical energy and forms biomass.
A farming system that avoids synthetic fertilizers, pesticides and genetically modified organisms, relying on manure, compost, crop rotation and biological pest control.
A fertilizer made from plant or animal material, such as manure, slurry, compost or bone meal, that releases nutrients slowly and adds organic matter to soil.
The carbon-based material in soil that comes from living things, including fresh litter, partly decomposed remains, humus and living soil organisms.
A value that lies far from the other values in a data set, which should be investigated and either explained or excluded with a stated reason.
A flow of energy or matter that crosses the boundary out of a system, such as heat lost by respiration or water leaving in a river.
Growing crops on the same land too often or too intensively, without returning nutrients or allowing rest, so soil fertility and structure decline.
The use of a renewable resource at a rate greater than its natural rate of replacement, so that the stock declines over time.
The removal of fish from a stock faster than the stock can replace them by reproduction and growth, so that the population declines over time.
Grazing by more livestock, or for longer, than the vegetation can withstand, so plant cover is lost and the soil is exposed to erosion.
A deep, highly weathered and leached soil of humid tropical regions such as rainforests, red or yellow from iron and aluminium oxides and low in nutrients.
A graph of dissolved oxygen against distance downstream of an input of organic pollution, showing a fall to a minimum and a gradual recovery as the organic matter is decomposed.
The reduction in stratospheric ozone caused mainly by chlorine and bromine from human-made ozone-depleting substances, which allows more UVB radiation to reach the Earth’s surface.
A region of severe seasonal ozone depletion over a pole in spring, usually defined as the area where total ozone falls below 220 Dobson units.
A human-made chemical, such as a CFC, halon, carbon tetrachloride, methyl bromide or HCFC, that reaches the stratosphere and releases chlorine or bromine that destroys ozone.