Glossary of Environmental Science - A

A

• abiotic - non-living chemical and physical factors of the environment (see also biotic).
• absorption pit (soakaway) – a hole dug in permeable ground and filled with broken stones or granular material and usually covered with earth allowing collected water to soak into the ground.
• absorption - one substance taking in another, either physically or chemically.
• acclimation - the process of an organism adjusting to chronic change in its environment.
• acid mine drainage - the outflow of acidic water from metal mines or coal mines.
• acid rain - rain or other forms of precipitation that is unusually acidic.
• adaptation - a characteristic of an organism that has been favoured by natural selection.
• adaptive radiation - closely related species that look very different, as a result of having adapted to widely different ecological niches.
• adsorption - one substance taking up another at its surface.
• aerobic - requiring air or oxygen; used in reference to decomposition processes that occur in the presence of oxygen.
• aerosols - solid or liquid particles suspended within the atmosphere.
• affluenza - as defined in the book of the same name 1. the bloated, sluggish and unfulfilled feeling that results from efforts to keep up with the Joneses. 2. an epidemic of stress, overwork, waste and indebtedness caused by dogged pursuit of the Australian dream. 3. an unsustainable addiction to economic growth. The traditional Western environmentally unfriendly high consumption life-style: a play on the words affluence and influenza cf. froogle, freegan.
• afforestation - planting new forests on lands that have not been recently forested.
• agroforestry - (sustainability) an ecologically based farming system, that, through the integration of trees in farms, increases social, environmental and economic benefits to land users.
• air pollution - the modification of the natural characteristics of the atmosphere by a chemical, particulate matter, or biological agent.
• albedo - reflectance; the ratio of light from the Sun that is reflected by the Earth's surface, to the light received by it. Unreflected light is converted to infrared radiation (heat), which causes atmospheric warming (see "radiative forcing"). Thus, surfaces with a high albedo, like snow and ice, generally contribute to cooling, whereas surfaces with a low albedo, like forests, generally contribute to warming. Changes in land use that significantly alter the characteristics of land surfaces can alter the albedo.
• algal bloom - the rapid and excessive growth of algae; generally caused by high nutrient levels combined with other favourable conditions. Blooms can deoxygenate the water leading to the loss of wildlife.
• alien species - see introduced species.
• alloy - composite blend of materials made under special conditions. Metal alloys like brass and bronze are well known but there are also many plastic alloys.
• alternative fuels - fuels like ethanol and compressed natural gas that produce fewer emissions than the traditional fossil fuels.
• anaerobic digestion - the biological degradation of organic materials in the absence of oxygen to yield methane gas (that may be combusted to produce energy) and stabilised organic residues (that may be used as a soil additive).
• anaerobic - not requiring air or oxygen; used in reference to decomposition processes that occur in the absence of oxygen.
• ancient forest - see old growth forest.
• anoxic - - with abnormally low levels of oxygen.
• anthropogenic - man-made, not natural.
• anthroposophy - spiritual philosophy based on the teachings of Rudolf Steiner (25 February 1861 – 30 March 1925) which postulates the existence of an objective, intellectually comprehensible spiritual world accessible to direct experience through inner development - more specifically through cultivating conscientiously a form of thinking independent of sensory experience. Steiner was the initiator of biodynamic gardening.
• application efficiency - (sustainability) the efficiency of watering after losses due to runoff, leaching, evaporation, wind etc.
• appropriated carrying capacity - another name for the Ecological Footprint, but often used in referring to the imported ecological capacity of goods from overseas.
• aquaculture - the cultivation of aquatic organisms under controlled conditions.
• aquifer – a bed or layer yielding water for wells and springs etc.; an underground geological formation capable of receiving, storing and transmitting large quantities of water. Aquifer types include: confined (sealed and possibly containing “fossil” water); unconfined (capable of receiving inflow); and Artesian (an aquifer in which the hydraulic pressure will cause the water to rise above the upper confining layer).
• arable land - land that can be used for growing crops.
• atmosphere – general name for the layer of gases around a material body; the Earth's atmosphere consists, from the ground up, of the troposphere (which includes the planetary boundary layer or peplosphere, the lowest layer), stratosphere, mesosphere, ionosphere (or thermosphere), exosphere and magnetosphere.
• autotroph - an organism that produces complex organic compounds from simple inorganic molecules using energy from light or inorganic chemical reactions.
• available water capacity – that proportion of soil water that can be readily absorbed by plant roots.
• avoidance – (sustainability) the first step in the waste hierarchy where waste generation is prevented (avoided).