accuracy: The degree to which a measurement or observation reflects the actual value. Compare with precision.

acid rain: The wet deposition only of acidifying substances from the atmosphere. See also acidifying deposition.

acid shock: An event of relatively acidic surface water that can occur in the springtime when the snowpack melts quickly but the ground is still frozen.

acid sulphate soil: Acidic soil conditions caused when certain wetlands are drained and sulfide compounds become oxidized.

acid-mine drainage: Acidic water and soil conditions that develop when sulfide minerals become exposed to the atmosphere, allowing them to be oxidized by Thiobacillus bacteria.

acid-neutralizing capacity: The quantitative ability of water to neutralize inputs of acid without becoming acidified. See also buffering capacity.

acidification: An increasing concentration of hydrogen ions (H+) in soil or water.

acidifying deposition: Both the wet and dry deposition of acidifying substances from the atmosphere.

acute toxicity: Toxicity associated with short-term exposures to chemicals in concentrations high enough to cause biochemical or anatomical damages, even death. Compare with chronic toxicity.

Adaptation: Focuses on the need for strategies to deal with the climate change that is unavoidable because of increased carbon already in the atmosphere.

additionality: The extent to which a new action (policy, project etc.) adds to the benefits or costs associated with existing conditions.

aerobic: Refers to an environment in which oxygen (O2) is readily available. Compare with anaerobic.

aesthetic pollution: Substantially a matter of cultural values, this commonly involves images that are displeasing to many (but not necessarily all) people.

afforestation: Establishment of a forest where one did not recently occur, as when trees are planted on agricultural land.

age-class structure: The proportions of individuals in various age classes of a population.

agricultural site capability: See site capability.

agroecosystem: An ecosystem used for the production of food.

agroforestry: The cultivation of trees in plantations, typically using relatively intensive management practices.

algal bloom: An event of high phytoplankton biomass.

ambient standard: A minimum level of overall environmental quality that must be reached.

ammonification: Oxidation of the organically bound nitrogen of dead biomass into ammonium (NH4+).

anaerobic: Refers to an environment in which oxygen (O2) is not readily available. Compare with aerobic.

angiosperm: Flowering plants that have their ovules enclosed within a specialized membrane and their seeds within a seedcoat. Compare with gymnosperm.

anthropocene: A term bestowed by Noble Laureate Paul Crutzen to describe the last 200-year period of human industrialization. The prefix “anthro” points to the decisive impact of human population growth and technological development on the planetary biosphere since 1800, as its principal agents of change superceding all other factors.

anthropocentric world view: This considers humans as being more worthy than other species and uniquely disconnected from nature. The importance and worth of everything is considered in terms of the implications for human welfare. Compare with biocentric world view and ecocentric world view.

anthropogenic: Occurring as a result of a human influence.

applied ecology: The application of ecological principles to deal with economic and environmental problems.

aquaculture: The cultivation of fish and other aquatic species.

aquifer: Groundwater resources in some defined area.

artificial selection: The deliberate breeding of species to enhance traits that are viewed as desirable by humans.

artificial wetland: An engineered wetland, usually constructed to treat sewage or other organic wastes.

aspect: The direction in which a slope faces.

assimilation efficiency: In an animal, the percentage of the energy content of ingested food that is absorbed across the gut wall. In plants, the percentage of solar visible light that is fixed by photosynthesis. The term may also be used to refer to the percentage assimilation of ingested inorganic nutrients (such as nitrate or phosphate) by plants or animals, or of drugs by animals.

atmosphere: The gaseous envelope surrounding the Earth, held in place by gravity.

atmospheric inversion (temperature inversion): A relatively stable atmospheric condition in which cool air is trapped beneath a layer of warmer air.

atmospheric water: Water occurring in the atmosphere, in vapour, liquid, or solid forms.

atom bomb: An explosive device that is based on the uncontrolled “splitting” of certain fissile isotopes of uranium and/or plutonium.

autecology: The field within ecology that deals with the study of individuals and species. Compare with synecology.

autotroph: An organism that synthesizes its biochemical constituents using simple inorganic compounds and an external source of energy to drive the process. See also primary producer, photoautotroph, and chemoautotroph.

available concentration: The concentration of metals in an aqueous extract of soil, sediment, or rocks, simulating the amount available for organisms to take up from the environment. Compare with total concentration.

avoided cost: A type of direct method that equates the value of an environmental improvement with a cost that can then be avoided.

baby boom: A period of high fecundity during 1945–1965 that occurred because of social optimism after the Second World War.

background concentration: A presence or concentration of a substance that is not significantly influenced by either anthropogenic emissions or unusual natural exposures.

benefit transfer: A method for estimating the value of a natural amenity by applying estimates from a complex study of a slightly different (but similar) amenity to the case at hand.

binomial: Two latinized words that are used to name a species.

bioaccumulation (bioconcentration): The occurrence of chemicals in much higher concentrations in organisms than in the ambient environment. Compare with food-web magnification.

biocentric world view: This considers all species (and individuals) as having equal intrinsic value. Humans are not considered more important or worthy than any other species. Compare with anthropocentric world view and ecocentric world view.

biocomplexity: A defining characteristic of living things and their relationships to each other. The biocomplexity concept emphasizes the multiple dependent connections within ecosystems, and between ecosystems and human societies.

bioconcentration: See bioaccumulation.

biodegradation: The breakdown of organic molecules into simpler compounds through the metabolic actions of microorganisms.

biodiversity: The richness of biological variation, including genetic variability as well as species and community richness.

biodiversity crisis: The present era of high rates of extinction and endangerment of biodiversity.

biogeochemical prospecting: Prospecting for metal ores using observations of high metal concentrations in plants, soil, or surface rocks.

biological control: Pest-control methods that depend on biological interactions, such as diseases, predators, or herbivores.

biological oxygen demand (BOD): The capacity of organic matter and other substances in water to consume oxygen during decomposition.

biomagnification: See food-web magnification.

biomass energy: The chemical potential energy of plant biomass, which can be combusted to provide thermal energy.

biome: A geographically extensive ecosystem, occurring throughout the world wherever environmental conditions are suitable.

biophilia: An innate love of people for nature

bio-resource: A renewable resource that is biological in character.

biosphere: All life on Earth, plus their ecosystems and environments.

birth control: Methods used to control fertility and childbirth.

BOD: See biological oxygen demand.

bog: An infertile, acidic, unproductive wetland that develops in cool but wet climates. Compare with fen.

boreal coniferous forest: A northern forest dominated by coniferous trees, usually species of fir, larch, pine, or spruce. See also boreal forest.

boreal forest (taiga): An extensive biome occurring in environments with cold winters, short but warm growing seasons, and moist soils, and usually dominated by coniferous trees.

broad-spectrum pesticide: A pesticide that is toxic to other organisms as well as the pest.

broadcast spray: A pesticide treatment over a large area.

browse: Broad-leaved shrubs that are eaten by herbivores such as hares and deer.

bryophyte: Simple plants that do not have vascular tissues nor a cuticle on their foliage.

by-catch: Inadvertent harvesting of a non-target species.

buffering capacity: The ability of a solution to resist changes in pH as acid or base is added.

calorie: A standard unit of energy, defined as the amount of energy needed to raise the temperature of one gram of pure water from 15°C to 16°C. Compare with joule.

carbon credits: Actions that help reduce the atmospheric concentration of CO2, such as fossil-fuel conservation and planting trees.

carbon neutrality: To be carbon neutral, the carbon emissions of a consumable product or human activity must either not involve the consumption of carbon-based energy (a difficult thing to achieve under our present regime), or offset that consumption through the drawdown of an equivalent amount of atmospheric carbon during its lifecycle.

carnivore (secondary consumer): An animal that hunts and eats other animals.

carrying capacity: The abundance of a species that can be sustained without the habitat becoming degraded.

chaparral: A shrub-dominated ecosystem that occurs in south- temperate environments with winter rains and summer drought.

chemical weapons: Weapons that cause deaths or injuries through exposure to toxic chemicals.

chemoautotroph: Microorganisms that harness some of the potential energy of certain inorganic chemicals (e.g., sulfides) to drive their fixation of energy through chemosynthesis. Compare with photoautotroph.

chemosynthesis: Autotrophic productivity that utilizes energy released during the oxidation of certain inorganic chemicals (such as sulfides) to drive biosynthesis. Compare with photosynthesis.

chromosome: Subcellular unit composed of DNA and containing the genetic information of eukaryotic organisms.

chronic toxicity: Toxicity associated with exposure to small or moderate concentrations of chemicals, sometimes over a long period of time. The damages may be biochemical or anatomical, and may include the development of a lethal disease, such as cancer. Compare with acute toxicity.

clear-cutting: The harvesting of all economically useful trees from an area at the same time.

climate: The prevailing, long-term, meteorological conditions of a place or region, including temperature, precipitation, wind speed, and other factors. Compare with weather.

climate change: Long-term changes in air, soil, or water temperature; precipitation regimes; wind speed; or other climate-related factors.

closed loops: The sustainable reform of industrial production and waste management emphasizes the recycling of materials back into the environment or into the industrial cycle, that is, to eliminate the concept of waste entirely.

coal: An organic-rich, solid fossil fuel mined from sedimentary geological formations.

coal washing: See fuel desulphurization.

coarse woody debris: Logs lying on the forest floor. 

coase theorem: The idea that with property rights and frictionless negotiation, private agents will bargain to reach efficient outcomes even in the face of externalities.

coevolution: This occurs when species interact in ways that affect their reciprocal survival, and so are subject to a regime of natural selection that reinforces their mutual evolutionary change.

collective properties: This term is used in reference to the summation of the parts of a system. See also emergent properties.

command and control: Regulations that set strict, specific guidelines to govern the behavior of polluters and resource users.

commensalism: A symbiosis in which one of the species benefits from the interaction, while the other is not affected in either a positive or negative way.

commercial energy production: The use of solid, liquid, and gaseous fuels, plus all electricity. Does not include the use of traditional fuels. See also total energy production and traditional fuels.

commercial extinction: Depletion of a natural resource to below the abundance at which it can be profitably harvested.

common but differentiated responsibilities: An ethical framework, promoted particularly by developing nations, that recognizes mitigation of global warming as a shared responsibility, but at the same time argues that the wealthy, industrialized countries of the West that have been the historical beneficiaries of carbon-based development should accept a greater burden for both reducing global carbon emissions, and providing developing nations with the technology and economic means to modernize in sustainable ways.

common pool resource: A resource that is open to all users, but which is highly rival in use.

common-property resource: A resource shared by all of society, not owned by any particular person or interest.

community: In ecology, this refers to populations of various species that are co-occurring at the same time and place.

community-replacing disturbance: A disturbance that results in the catastrophic destruction of an original community, and its replacement by another one. Compare with microdisturbance.

compaction: A decrease in the pore space of soil (or increased bulk density) caused by the passage of heavy machinery.

compartment: A reservoir of mass in a nutrient or material cycle.

competition: A biological interaction occurring when the demand for an ecological resource exceeds its limited supply, causing organisms to interfere with each other.

competitor: A species that is dominant in a habitat in which disturbance is rare and environmental stresses are unimportant, so competition is the major influence on evolution and community organization.

compost: Partially decomposed, well-humified organic material

composting: The processing of discarded organic material by encouraging decomposition processes under warm, moist, oxygen-rich conditions. The product, known as compost, is a useful fertilizer and soil conditioner. 

conjoint analysis: A stated preference valuation tool that allows an analyst to estimate the marginal values of multiple attributes of an environmental good.

connectivity: An important feature of complex systems. Connections exist between even apparently remote and disparate things. For example, drought in Australia might impact the price of bread in Egypt, which in turn has repercussions for U.S. foreign policy.

conservation: Wise use of natural resources. Conservation of nonrenewable resources involves recycling and other means of efficient use. Conservation of renewable resources includes these means, in addition to ensuring that harvesting does not exceed the rate of regeneration of the stock.

contamination: The presence of potentially damaging chemicals in the environment, but at concentrations less than those required to cause toxicity or other ecological damages. Compare with pollution.

contingent valuation: A stated preference valuation tool that describes a single environmental good and elicits survey responses from which the analyst can estimate people’s value for that good.

control (control treatment): An experimental treatment that was not manipulated, and is intended for comparison with manipulated treatments.

conventional economics: Economics as it is commonly practiced, which includes not accounting for costs associated with ecological damages and resource depletion. Compare with ecological economics.

conventional munitions: Explosive devices that are based on chemical reactions, such as cordite and dynamite.

convergence (evolutionary conversion): This occurs when unrelated species with similar niches and living in comparable environments are subjected to parallel regimes of natural selection, resulting in their evolution to be similar in morphology, physiology, and behavior.

conversion: See ecological conversion.

core: Earth’s massive interior, made up of hot molten metals.

Coriolis effect: An influence of Earth’s west-to-east rotation, which makes winds in the Northern Hemisphere deflect to the right and those in the Southern Hemisphere to the left.

Cornucopian: The view that economic growth and technological innovation will continue to improve the conditions of humanity as they have done for the past 500 years, and that no environmental constraints are important or permanent.

cost-benefit analysis: Evaluation of how the overall benefits of a project compare to its costs.

cost-effective: As inexpensive as possible; cost minimizing.

counterfactual: The scenario against which a different scenario should be compared; in policy analysis, the way the world would have been in the absence of the policy.

creationist: A person who rejects the theory of evolution in favor of a literal interpretation of Genesis, the first book of the Old Testament of the Bible. See also scientific creationist.

critical load: A threshold for pollutant inputs, below which it is thought ecological damages will not be caused.

crude oil: See petroleum.

crude oil washing (COW) method: A method of washing a tanker’s oil-storage components with a spray of crude oil before the next cargo is loaded. This eliminates the use of wash-water and avoids an important cause of marine oil pollution.

crust: The outermost layer of Earth’s sphere, overlying the lithosphere and composed mostly of crystalline rocks.

cultural eutrophication: Eutrophication caused by anthropogenic nutrient inputs, usually through sewage dumping or fertilizer runoff. See also eutrophication.

cultural evolution: Adaptive evolutionary change in human society, characterized by increasing sophistication in the methods, tools, and social organizations used to exploit the environment and other species. Compare with evolution.

cultural identity: A complex of self-identified characteristics and values that a group of people considers important in defining their distinct quality.

culture: The shared beliefs, values, and knowledge of a defined group of people.

cumulative environmental impacts: Environmental impacts that result from a proposed undertaking, in addition to those caused by any past, existing, and imminent developments and activities.

deadweight loss: The extent to which net benefits are lower than they could be.

decay: The decomposition or oxidation of dead biomass, mostly through the actions of microorganisms.

decomposer: See detritivore.

deductive logic: Logic in which initial assumptions are made and conclusions are then drawn from those assumptions. Compare with inductive logic.

deep drainage: Soil water that has drained to below the lower limits of plant roots.

deforestation: A permanent conversion of forest into some other kind of ecosystem, such as agriculture or urbanized land use.

demographic transition: A change in human population parameters from a condition of high birth and death rates to one of low birth and death rates.

denitrification: The microbial reduction of nitrate (NO3–) into gaseous N2O or N2.

desert: A temperate or tropical biome characterized by prolonged drought, usually receiving less than 25 cm of precipitation per year.

desertification: The increasing aridity of drylands; an environmental change that can make agriculture difficult or impossible.

detritivore: A heterotroph that feeds on dead organic matter.

developed countries: Countries with a relatively well-organized economic infrastructure and a high average per-capita income. See also high-income countries and compare with less-developed countries.

development (economic development): An economic term that implies improving efficiency in the use of materials and energy in an economy, and progress toward a sustainable economic system. Compare with economic growth.

diachronic: A diachronic view of a system examines its evolution over time. 

direct methods: Valuation tools that use data on actual market transactions to estimate the value of a change in the environment.

discipline: A specific area of study, such as mathematics or music.

discounting: The process of converting future values (costs or benefits) into an equivalent amount of money received today; controls for human time preference.

disturbance: An episode of destruction of some part of a community or ecosystem.

DNA: The biochemical deoxyribonucleic acid, the main constituent of the chromosomes of eukaryotic organisms.

domestication: The genetic, anatomic, and physiological modification of crops and other species from their wild, progenitor species, through the selective breeding of preferred races (or cultivars).

dose-response relationship: The quantitative relationship between different doses of a chemical and a biological or ecological response.

doubling time: The time it takes for something to increase by a factor of two (as in population growth).

drift: Movement of applied pesticide off the intended site of deposition through atmospheric or aquatic transport.

dry deposition: Atmospheric inputs of chemicals occurring in intervals between rainfall or snowfall. Compare with wet deposition.

dumping: The long-term disposal of disused material, for example, by placing solid waste into a sanitary landfill, or by discarding liquid waste into a waterbody.

earthquake: A trembling or movement of the earth, caused by a sudden release of geological stresses at some place within the crust.

ecocentric world view: This incorporates the biocentric world view but also stresses the importance of interdependent ecological functions, such as productivity and nutrient cycling. In addition, the connections among species within ecosystems are considered to be invaluable. Compare with anthropocentric world view and biocentric world view.

ecofeminism: A philosophical and political movement that applies feminist ideas to environmental concerns.

ecological conversion: A long-term change in the character of the ecosystem at some place, as when a natural forest is converted into an agricultural land use.

ecological economics: A type of economics that involves a full accounting of costs associated with ecological damages and resource depletion. Compare with conventional economics.

ecological footprint: The area of ecoscape (i.e., landscape and seascape) required to supply a human population with the necessary food, materials, energy, waste disposal, and other crucial goods and services.

ecological integrity (ecosystem health): A notion related to environmental quality, but focusing on changes in natural populations and ecosystems, rather than effects on humans and their economy. See also environmental quality.

ecological justice: A worldview in which all species (i.e., not just humans) have a right to equitable access to the necessities of life and happiness. See also social justice.

ecological pyramid: A model of the trophic structure of an ecosystem, organized with plant productivity on the bottom, that of herbivores above, and carnivores above the herbivores.

ecological service: An ecological function that is useful to humans and to ecosystem stability and integrity, such as nutrient cycling, productivity, and control of erosion.

ecological stress: See stressors.

ecological sustainability: See ecologically sustainable development.

ecological values: Broader utilitarian values that are based on the needs of humans, but also on those of other species and natural ecosystems.

ecologically sustainable development: This considers the human need for resources within an ecological context, and includes the need to sustain all species and all components of Earth’s life-support system. Compare with sustainable development.

ecologically sustainable economic system: An economic system that operates without a net consumption of natural resources, and without endangering biodiversity or other ecological values. Ultimately, ecologically sustainable economic systems are supported by the wise use of renewable resources.

ecologically sustainable economy: An economy in which ecological goods and services are utilized in ways that do not compromise their future availability and do not endanger the survival of species or natural ecosystems.

ecology: The study of the relationships between organisms and their environment.

economic development: See development.

economic growth: A term that refers to an economy that is increasing in size over time, usually due to increases in both population and per capita resource use. Compare with development.

ecoregion: See ecozone.

ecoscape: A general term for landscapes or seascapes.

ecosystem: A general term used to describe one or more communities that are interacting with their environment as a defined unit. Ecosystems range from small units occurring in microhabitats, to larger units such as landscapes and seascapes, and even the biosphere.

ecosystem approach: A holistic interpretation of the natural world that considers the web-like interconnections among the many components of ecosystems.

ecosystem health: See ecological integrity.

ecosystem services: Resources and processes through which the environment gives benefits to humanity.

ecotone: A zone of transition between two distinct habitats.

ecotoxicology: Study of the directly poisonous effects of chemicals in ecosystems, plus indirect effects such as changes in habitat or food abundance caused by toxic exposures. Compare with toxicology and environmental toxicology.

ecotype: A population specifically adapted to coping with locally stressful conditions, such as soil with high metal concentrations.

ecozone: The largest biophysical zones in the national ecological classification of Canada.

efficient: Having the feature that net benefits are maximized.

electromagnetic energy: Energy associated with photons, comprising an electromagnetic spectrum divided into components, including ultraviolet, visible, and infrared.

emergent property: A used in reference to synergetic properties that are greater than the summation of the parts of a system. See also collective properties.

emissions trading: A system in which a company that has not exceeded its cap on emissions of a regulated substance, such as SO2, can sell its “surplus” to another that is likely to exceed its cap.

endangered: Indigenous species threatened with imminent extinction or extirpation over all or a significant portion of their range.

endemic: An ecological term used to describe species with a local geographic distribution.

energy: The capacity of a body or system to accomplish work, and existing as electromagnetic, kinetic, and potential energies.

energy budget: An analysis of the rates of input and output of energy to a system, plus transformations of energy among its states, including changes in stored quantities.

energy production: See total energy production.

entropy: A physical attribute related to the degree of randomness of the distributions of matter and energy.

environment (the): (1) Refers to influences on organisms and ecosystems, including both non-living (abiotic) and biological factors; (2) An indeterminate word for issues associated with the causes and consequences of environmental damage, or with the larger environmental crisis.

environmental citizenship: Actions taken by individuals and families to lessen their impacts on the environment.

environmental degradation: Refers to pollution, disturbance, resource depletion, lost biodiversity, and other kinds of environmental damage; usually refers to damage occurring accidentally or intentionally as a result of human activities (see also anthropogenic), but can also be caused by natural disasters or stressors.

environmental discrimination (environmental prejudice): Discrimination against any defined group that results in them suffering a disproportionate amount of degradation or pollution of their living or work environment. See also environmental racism.

environmental ecology: See applied ecology

environmental education: A way of fostering environmental literacy by incorporating environmental issues in educational curricula, both in specialized classes as well as across the curriculum, and also including the out-of-school public.

environmental ethics: These deal with the responsibilities of the present human generation to ensure continued access to adequate resources and livelihoods for future generations of people and other species.

environmental impact assessment (EIA): A process used to identify and evaluate the potential consequences of proposed actions or policies for environmental quality. See also socioeconomic impact assessment.

environmental indicators: Relatively simple measurements that are sensitive to changes in the intensity of stressors, and are considered to represent complex aspects of environmental quality.

environmental literacy: Refers to an objective understanding, by individuals and society-at-large, of the causes and consequences of environmental problems.

environmental monitoring: Repeated measurements of indicators related to the inorganic environment or to ecosystem structure and function.

environmental mutagen: A mutagenic influence that is encountered in the environment. See also mutagen.

environmental non-governmental organizations (ENGOs): Charities and other not-for-profit organizations that are working in the environmental field. See also non-governmental organizations.

environmental quality: A notion related to the amounts of toxic chemicals and other stressors in the environment, to the frequency and intensity of disturbances, and to their effects on humans, other species, ecosystems, and economies.

environmental racism: Discrimination against a group of people defined by racial attributes, which results in them suffering a disproportionate amount of degradation or pollution of their living or work environment. See also environmental discrimination.

environmental reporting: Communication of information about changes in environmental quality to interest groups and the general public.

environmental risk: A hazard or probability of suffering damage or misfortune because of exposure to some environmental circumstance.

environmental risk assessment: A quantitative evaluation of the risks associated with an environmental hazard.

environmental science: An interdisciplinary branch of science that investigates questions related to the human population, resources, and damages caused by pollution and disturbance.

environmental scientist: A scientist who is specialized in some aspect of environmental science.

environmental security: The protection of people and the public interest from environmental risks, particularly those associated with anthropogenic activities and accidents, but may also include natural dangers.

environmental stressor: See stressor.

environmental studies: An extremely interdisciplinary approach that examines the scientific, social, and cultural aspects of environmental issues.

environmental teratogen: A teratogenic influence that is encountered in the environment. See also teratogen.

environmental toxicology: The study of environmental factors influencing exposures of organisms to potentially toxic levels of chemicals. Compare with toxicology and ecotoxicology.

environmental values: Perceptions of the worth of environmental components, divided into two broad classes: utilitarian and intrinsic.

environmentalist: Anyone with a significant involvement with environmental issues, usually in an advocacy sense.

erosion: The physical removal of rocks and soil through the combined actions of flowing water, wind, ice, and gravity.

estuary: A coastal, semi-enclosed ecosystem that is open to the sea and has habitats transitional between marine and freshwater conditions.

ethics: The perception of right and wrong. The proper behavior of people toward each other and toward other species and nature.

eukaryote: Organisms in which the cells have an organized, membrane-bound nucleus containing the genetic material. Compare with prokaryote.

eutrophic: Pertains to waters that are highly productive because they contain a rich supply of nutrients. Compare with oligotrophic and mesotrophic.

eutrophication: Increased primary productivity of an aquatic ecosystem, resulting from nutrient inputs.

evaporation: The change of state of water from a liquid or solid to a gas.

evapotranspiration: Evaporation of water from a landscape. See also transpiration.

evolution: Genetically based changes in populations of organisms, occurring over successive generations.

evolutionary ecology: The interpretation of ecological knowledge in terms of evolution, natural selection, and related themes.

experiment: A controlled test or investigation designed to provide evidence for, or preferably against, a hypothesis about the natural or physical world.

exposure: In ecotoxicology, this refers to the interaction of organisms with an environmental stressor at a particular place and time.

exposure assessment: An investigation of the means by which organisms may encounter a potentially toxic level of a chemical or other environmental stressor.

extant: A species that still exists. Compare with extinct.

externality: A cost or benefit that is received, even though the affected party did not choose to incur it.

externality tax: A tax on something that causes negative externalities.

extinct (extinction): A condition in which a species or other taxon no longer occurs anywhere on Earth.

extinction crisis: See biodiversity crisis.

extinction vortex: An accelerating spiral of endangerment and extinction caused by worsening environmental conditions.

extirpated (extirpation): A condition in which a species or other taxon no longer occurs in some place or region, but still survives elsewhere.

fact: An event or thing known to have happened, to exist, or to be true.

fen: A wetland that develops in cool and wet climates, but is less acidic and more productive than a bog because it has a better nutrient supply. Compare with bog.

first law of thermodynamics: A physical principle stating that energy can undergo transformations among its various states, but it is never created or destroyed; thus, the energy content of the universe remains constant. See also second law of thermodynamics.

First Nations: The Aboriginal people(s) originally living in some place. This term is often used in reference to the original inhabitants of the Americas, prior to the colonization of those regions by Europeans, and their modern descendants.

fission bomb: See atom bomb.

fission reaction: Nuclear reaction involving the splitting of heavier, radioactive atoms into lighter ones, with the release of large quantities of energy.

fitness: The proportional contribution of an individual to the progeny of its population.

flow-through system: A system with an input and an output of energy or mass, plus temporary storage of any difference.

flue-gas desulphurization: A process to remove SO2 from the waste (flue) gases of a power plant or smelter, before they are discharged into the atmosphere.

flux: A movement of mass or energy between compartments of a material or energy cycle.

food chain: A hierarchical model of feeding relationships among species in an ecosystem.

food web: A complex model of feeding relationships, describing the connections among all food chains within an ecosystem.

food-web magnification (food-web accumulation, food-web concentration): The tendency for top predators in a food web to have the highest residues of certain chemicals, especially organochlorines. Compare with bioaccumulation.

forest floor: Litter and other organic debris lying on top of the mineral soil of a forest.

forestry: The harvesting of trees and management of post-harvest succession to foster the regeneration of another forest.

fossil fuel: Organic-rich geological materials, such as coal, petroleum, and natural gas. 

free rider: A person who does not contribute to a public good in hopes that they can benefit from provision by other people.

frontier world view: This asserts that humans have a right to exploit nature by consuming natural resources in boundless quantities. See also sustainability world view and spaceship world view.

fuel desulphurization: A process that removes much of the sulfur content of coal before it is used as a fuel in a power plant.

fuel switching: The replacement of a high-sulfur fuel, such as coal, by an energy source that does not emit sulfur gases, such as hydroelectricity or nuclear power.

full-cost accounting system: An accounting system that considers all costs, including those of environmental damage.

fungicide: A pesticide used to protect crop plants and animals from fungi that cause diseases or other damages.

fusion bomb: See hydrogen bomb.

fusion reaction: Nuclear reaction involving the combining of light nuclei, such as those of hydrogen, to make heavier ones, with the release of large quantities of energy. Fusion reactions occur under conditions of intense temperature and pressure, such as within stars and in hydrogen bombs.

Gaia hypothesis: A notion that envisions Earth’s species and ecosystems as a “superorganism” that attempts to optimize environmental conditions toward enhancing its own health and survival.

gaseous wastes: The gaseous products of combustion or industrial reactions.

gene: A region of a chromosome, containing a length of DNA that behaves as a particulate unit in inheritance and determines the development of a specific trait.

genocide: The mass killing of an identifiable group as an attempted extermination.

genotype: The genetic complement of an individual organism. See also phenotype.

geography: The study of the features of the surface of the Earth, including topography, landforms, soil, climate, and vegetation, as well as the intersections of these with the economic interests of humans.

geothermal energy: Heat in Earth’s crust, which can sometimes be used to provide energy for heating or generation of electricity.

glaciation: An extensive environmental change associated with an extended period of global climatic cooling and characterized by advancing ice sheets.

glacier: A persistent sheet of ice, occurring in the Arctic and Antarctic and at high altitude on mountains.

greater protected area: A protected area plus its immediately surrounding area, co-managed to sustain populations of indigenous species and natural communities.

green manure: Living plant biomass that is grown and then incorporated into the soil by tillage.

green revolution: Intensive agricultural systems involving the cultivation of improved crop varieties in monoculture, and increased use of mechanization, fertilizers, and pesticides.

greenhouse effect: The physical process by which infrared-absorbing gases (such as CO2) in Earth’s atmosphere help to keep the planet warm.

greenhouses gases (GHGs): Atmospheric gases that efficiently absorb infrared radiation and then dissipate some of the thermal energy gain by re-radiation. Synonym: ** radiatively active gases.

gross domestic product (GDP): The total annual value of all goods and services produced domestically within a country. GDP is equivalent to gross national product minus net investment income from foreign countries. See also gross national product (GNP).

gross national product (GNP): The total annual value of all goods and services produced domestically by a country, including net foreign investment income. See also gross domestic product (GDP).

gross primary production (GPP): The fixation of energy by primary producers within an ecosystem. See also respiration, net primary production, and autotroph.

groundwater: Water stored underground in soil and rocks.

groundwater drainage: The drainage of water to storage places in the ground, occurring under the influence of gravity.

growth: Refers to an economy or economic sector that is increasing in size over time. Compare with development.

gymnosperm: Vascular plants such as conifers, which have naked ovules not enclosed within a specialized membrane, and seeds without a seedcoat. Compare with angiosperm.

habitat: The place or “home” where a plant or animal lives, including the specific environmental factors required for its survival.

harvesting effort: The amount of harvesting, which is a function of both the means (such as the kinds of fishing gear) and the intensity (the number of boats and the amount of time each spends fishing).

harvesting mortality: Anthropogenic mortality, especially that due to the harvesting of a bio-resource. Compare with natural mortality.

hazardous waste: Wastes that are flammable, explosive, toxic, or otherwise dangerous. See also toxic waste.

hedonic price analysis: A revealed preference tool that uses data on house prices and characteristics to estimate the value of features of the environment that vary among houses.

hedonic wage analysis: A revealed preference tool that uses data on wages and risk of death by job type estimate willingness to pay to reduce the risk of death.

herbicide: A pesticide used to kill weeds. See also weed.

herbivore (or primary consumer): An animal that feeds on plants.

heterotroph: An organism that utilizes living or dead biomass as food.

hidden injury: A reduction in plant productivity caused by exposure to pollutants, but not accompanied by symptoms of acute tissue damages.

high-income countries: Countries with a relatively high average per-capita income. See also developed countries and compare with low-income countries.

hormone: A biochemical produced in an endocrine gland (and transported by the blood) that functions to regulate a metabolic process. Some chemicals in food may mimic the function of hormones produced naturally in the body.

hormonally active substance: A hormone or another chemical that has an effect on the regulation of biochemistry. See also hormone.

humidity: The actual concentration of water in the atmosphere, usually measured in mg/m3. Compare with relative humidity.

humus: Amorphous, partially decomposed organic matter. An important and persistent type of soil organic matter, it is very important in soil tilth and fertility.

hydrocarbons: Molecules composed of hydrogen and carbon only.

hydroelectric energy: Electricity generated using the kinetic energy.

hydrogen bomb: A nuclear weapon that is based on the fusion of nuclei of deuterium and tritium, two isotopes of hydrogen.

hydrologic (water) cycle: The movement between, and storage of water in, various compartments of the hydrosphere. See also hydrosphere.

hydrosphere: The parts of the planet that contain water, including the oceans, atmosphere, on land, in surface waterbodies, underground, and in organisms.

hyperaccumulator: A species that bioaccumulates metals or other chemicals to extremely high concentrations in their tissues. See also bioaccumulation.

hypereutrophic: Extremely eutrophic waters; usually considered to be a degraded ecological condition. See also eutrophic.

hypersensitivity: An extreme sensitivity to exposure to some environmental factor, resulting in a biological response such as asthma, disease, or even death. It may be expressed at the species or individual level, and it involves responses at relatively low intensities of exposure that the great majority of species or individuals could tolerate.

hypothesis: A proposed explanation for the occurrence or causes of natural phenomena. Scientists formulate hypotheses as statements, and test them through experiments and other forms of research.

igneous rock: Rock such as basalt and granite, formed by cooling of molten magma.

impoundment: An area of formerly terrestrial landscape that is flooded behind a dam.

incineration: The combustion of mixed solid wastes to reduce the amount of organic material present.

indicator: See environmental indicator.

indigenous culture: A human culture existing in a place or region prior to its invasion, or other significant influence, by a foreign culture.

individual organism: A genetically and physically discrete living entity.

inductive logic: Logic in which conclusions are objectively developed from the accumulating evidence of experience and the results of experiments. See also deductive logic.

inequitable: Not equitable or fair.

inherent value: See intrinsic value

inhumane: Reflecting a lack of pity or compassion; most commonly refers to the cruel treatment by humans of other animals.

insecticide: A pesticide used to kill insects that are considered pests. See also pesticide and pest. 

interdisciplinarity: A trend in higher education research and teaching of the last thirty years that emphasizes the bridging of traditional disciplines, and that is an essential framework for sustainability studies.

instrumental value: See utilitarian value

instrumentalist: An attitude to environmental resources characteristic of the last 500-year period of global human economic development, whereby ecosystem provisions—water, minerals, oil and gas, etc.—are perceived only in terms of their use value to human beings, rather than as integral elements of a wider natural system.

integrated forest management: Forest management plans that accommodate the need to harvest timber from landscapes, while also sustaining other values, such as hunted wildlife, outdoor recreation, and biodiversity.

integrated pest management (IPM): The use of a variety of complementary tactics toward pest control, with the aim of having fewer environmental and health risks.

interdisciplinary: Encompassing a wide diversity of kinds of knowledge.

intrinsic population change: Population change due only to the balance of birth and death rates.

intrinsic value: Value that exists regardless of any direct or indirect value in terms of the needs or welfare of humans.

invasive alien: Refers to non-native species that survive in wild habitats and possibly aggressively out-compete native species or cause other kinds of ecological damage.

inversion: See atmospheric inversion.

invertebrate: Any animal that lacks an internal skeleton, and in particular a backbone.

joule: A standard unit of energy, defined as the energy needed to accelerate 1 kg of mass at 1 m/s2 for a distance of 1 meter. Compare with calorie.

K-selected: Refers to organisms that produce relatively small numbers of large offspring. A great deal of parental investment is made in each progeny, which helps to ensure their establishment and survival. Compare with r-selected.

keystone species: A dominant species in a community, usually a predator, with an influence on structure and function that is highly disproportionate to its biomass.

kinetic energy: Energy associated with motion, including mechanical and thermal types.

knowledge: Information and understanding about the natural world.

landscape: The spatial integration of ecological communities over a large terrestrial area.

landscape ecology: Study of the spatial characteristics and temporal dynamics of communities over large areas of land (landscapes) or water (seascapes).

laws of thermodynamics: Physical principles that govern all transformations of energy. See also first law of thermodynamics and second law of thermodynamics.

leaching: The movement of dissolved substances through the soil with percolating rainwater.

lentic ecosystem: A freshwater ecosystem characterized by nonflowing water, such as a pond or lake. Compare with lotic ecosystem.

less-developed countries: Countries with a relatively well-organized economic infrastructure and a high average per-capita income. See also high-income countries and compare with developed countries.

liability: A legal construct meaning that an agent is held responsible by the courts to pay when that agent does something that imposes costs on other people in society.

life form: A grouping of organisms on the basis of their common morphological and physiological characteristics, regardless of their evolutionary relatedness.

life index (production life): The known reserves of a resource divided by its current rate of production.

lifecycle: In terms of sustainability, the entire lifecycle of a product must be measured for its environmental impact, not simply its point of production, consumption, or disposal. A key aspect of general sustainability education is the understanding of where goods originate, the industrial processes required for their manufacture and transport, and their fate after use.

liming: Treatment of a waterbody or soil to reduce acidity, usually by adding calcium carbonate or calcium hydroxide.

limiting factor: An environmental factor that is the primary restriction on the productivity of autotrophs in an ecosystem. See also Principle of Limiting Factors.

liquid waste: Variable urban wastes that include sewage and discarded industrial and household fluids.

lithification: A geological process in which materials are aggregated, densified, and cemented into new sedimentary rocks.

lithosphere: An approximately 80-km thick region of rigid, relatively light rocks that surround Earth’s plastic mantle.

load-on-top (LOT) method: A process used in ocean-going petroleum tankers to separate and contain most oily residues before ballast waters are discharged to the marine environment.

long-range transport of air pollutants: See LRTAP.

lotic ecosystem: A freshwater ecosystem characterized by flowing water, such as a stream or river. Compare with lentic ecosystem.

low-income counties: Countries with a relatively small average per-capita income. See also less-developed countries and compare with high-income countries.

LRTAP: The long-range transport of atmospheric pollutants.

macroclimate: Climatic conditions affecting an extensive area. Compare with microclimate.

macroevolution: The evolution of species or higher taxonomic groups, such as genera, families, or classes. Compare with microevolution.

management system: A variety of management practices used in a coordinated manner.

manipulative experiment: An experiment involving controlled alterations of factors hypothesized to influence phenomena, conducted to investigate whether predicted responses will occur, thereby uncovering causal relationships. See also experiment and natural experiment.

mantle: A less-dense region that encloses Earth’s core, and composed of minerals in a hot, plastic state known as magma.

marginal benefit: The additional benefit of doing one more unit of something.

marginal cost: The additional cost of doing one more unit of something.

market failure: A condition that causes a market not to yield the efficient outcome.

marsh: A productive wetland, typically dominated by species of monocotyledonous angiosperm plants that grow as tall as several meters above the water surface.

mass extinction: An event of synchronous extinction of many species, occurring over a relatively short period of time. May be caused by natural or anthropogenic forces.

maximum sustainable yield (MSY): The largest amount of harvesting that can occur without degrading the productivity of the stock.

mechanization: The use of specialized machinery to perform work, instead of the labor of people or animals.

megacity: A large city, sometimes defined as having a population greater than 8 million people.

mesosphere: The layer of the atmosphere extending beyond the stratosphere to about 75 km above the surface of the Earth. See also stratosphere.

mesotrophic: Pertains to aquatic ecosystems of moderate productivity, intermediate to eutrophic and oligotrophic waters. Compare with eutrophic and oligotrophic.

metal: Any relatively heavy element that in its pure state shares electrons among atoms, and has useful properties such as malleability, high conductivity of electricity and heat, and tensile strength.

metamorphic rock: Rock formed from igneous or sedimentary rocks that have changed in structure under the influences of geological heat and pressure.

meteorite: An extraterrestrial rock-like object; very rarely, one may intersect with Earth’s orbit and impact the planet.

microclimate: Climatic conditions on a local scale. Compare with macroclimate.

microdisturbance: Local disruptions that affect small areas within an otherwise intact community. Compare with community-replacing disturbance.

microevolution: Relatively subtle evolutionary changes occurring within a population or species, sometimes within only a few generations, and at most leading to the evolution of races, varieties, or subspecies. Compare with macroevolution.

middle-income countries: Countries with a rapidly increasing average per-capita income. See also high-income and low-income countries and compare with developed countries and less-developed countries.

mitigation: An action that repairs or offsets environmental damages to some degree.

monoculture: The cultivation of only one species while attempting to exclude others from the agroecosystem.

montane forest: A conifer-dominated forest occurring below the alpine zone on mountains.

morbidity: The relative frequency of occurrence of a disease.

mortality: The number of deaths that occur at a specific time, in a specific group, or from a specific cause.

MSY: See maximum sustainable yield.

mutagen: A chemical or physical agent (e.g., ultraviolet radiation) that is capable of inducing genetic mutations.

mutualism (mutualistic symbiosis): A symbiosis in which both partners benefit.

natural: Refers to a non-anthropogenic context, i.e., one that is not influenced by humans and is self-organizing and dominated by native species; see also nature.

natural capital: See natural resource

natural experiment: An experiment conducted by observing variations of phenomena in nature, and then developing explanations for these through analysis of potential causal mechanisms. See also experiment and manipulative experiment.

natural gas: A gaseous, hydrocarbon-rich mixture mined from certain geological formations.

natural mortality: Mortality due to natural causes. Compare with harvesting mortality.

natural population change: A change in population that is due only to the difference in birth and death rates, and not to immigration or emigration.

natural resource: A source of material or energy that is extracted (harvested) from the environment.

natural selection: A mechanism of evolution, favoring individuals that, for genetically based reasons, are better adapted to coping with environmental opportunities and constraints. These more fit individuals have an improved probability of leaving descendants, ultimately leading to genetically based changes in populations, or evolution.

nature: Refers to the entire system of physical and biological existence and organization, uninfluenced by humans; see also natural. 

negative externality: A cost that is borne by someone who did not agree to the activity that caused the cost.

net benefits: The difference between total benefits and total costs.

net ecosystem productivity: The amount of ecosystem-level productivity that remains after respiration is subtracted from gross productivity.

net present value: The present discounted value of a stream of net benefits.

net primary production (NPP): Primary production that remains as biomass after primary producers have accounted for their respiratory needs. See also respiration and gross primary production.

niche: The role of a species within its community.

NIMBY: An acronym for “not in my backyard”.

nitrification: The bacterial oxidation of ammonium (NH4+) to nitrate (NO3–).

nitrogen fixation: The oxidation of nitrogen gas (N2) to ammonia (NH3) or nitric oxide (NO).

noise pollution: When the level of ambient sound becomes distracting to the normal activities of people. At a higher intensity it can cause hearing impairment.

non-governmental organizations (NGOs): Charities and other not- for-profit organizations. See also environmental non-governmental organizations.

nonlinear: Changes in a system are nonlinear when they exhibit sudden changes in rate of increase or decline. The population of a particular tropical frog species, for example, may suddenly crash as a result of warming temperatures, rather than show gradual decline.

non-renewable resource (non-renewable natural resource): A resource present on Earth in finite quantities, so as it is used, its future stocks are diminished. Examples are metals and fossil fuels. Compare with renewable resources.

non-target damage: Damage caused by a pesticide to non-target organisms. See also broad-spectrum pesticide and non-target organism.

non-target organism: Organisms that are not pests, but which may be affected by a pesticide treatment. See also broad-spectrum pesticide and non-target damage.

non-use values: Values people have for nature that do not stem from direct interaction.

normalization: An acquired evolutionary trait characteristic of human beings, whereby even radical changes are quickly adapted to and represented as normal.

normative analysis: A study of how things should be.

not in my backyard: See NIMBY.

nuclear fuel: Unstable isotopes of uranium (235U) and plutonium (239Pu) that decay through fission, releasing large amounts of energy that can be used to generate electricity.

nuclear winter: A period of prolonged climate cooling that might be caused by a nuclear war.

null hypothesis: A hypothesis that seeks to disprove a hypothesis.

nutrient: Any chemical required for the proper metabolism of organisms.

nutrient budget: A quantitative estimate of the rates of nutrient input and output for an ecosystem, as well as the quantities present and transferred within the system.

nutrient capital: The amount of nutrients present in a site in soil, living vegetation, and dead organic matter.

nutrient cycling: Transfers and chemical transformations of nutrients in ecosystems, including recycling through decomposition.

ocean: The largest hydrological compartment, accounting for about 97% of all water on Earth.

old-growth forest: A late-successional forest characterized by the presence of old trees, an uneven-aged population structure, and a complex physical structure.

oligotrophic: Pertains to aquatic ecosystems that are highly unproductive because of a sparse supply of nutrients. Compare with eutrophic and mesotrophic.

omnivore: An animal that feeds on both plant and animal materials. 

opportunity cost: The cost of foregoing the next best choice when making a decision.

organic agriculture: Systems by which crops are grown using natural methods of maintaining soil fertility, and pest-control methods that do not involve synthetic pesticides.

orographic precipitation: Precipitation associated with hilly or mountainous terrain that forces moisture-laden air to rise in altitude and become cooler, causing water vapor to condense into droplets that precipitate as rain or snow.

outer space: Regions beyond the atmosphere of Earth.

over-harvesting (over-exploitation): Unsustainable harvesting of a potentially renewable resource, leading to a decline of its stocks.

oxidizing smog: An event of air pollution rich in ozone, peroxy acetyl nitrate, and other oxidant gases.

paradigm: A pattern or model; a collection of assumptions, concepts, practices, and values that constitutes a way of viewing reality, especially for an intellectual community that shares them.

parameter: One or more constants that determine the form of a mathematical equation. In the linear equation Y = aX + b, a and b are parameters, and Y and X are variables. See also variable.

parasitism: A biological relationship involving one species obtaining nourishment from a host, usually without causing its death.

performance standard: A regulation specifying something about the outcome of private behaviors.

persistence: The nature of chemicals, especially pesticides, to remain in the environment before eventually being degraded by microorganisms or physical agents such as sunlight and heat.

pest: Any organism judged to be significantly interfering with some human purpose.

pesticide: A substance used to poison pests. See also pest, fungicide, herbicide, and insecticide.

pesticide treadmill: The inherent reliance of modern agriculture and public-health programs on pesticides, often in increasing quantities, to deal with pest problems.

petroleum (crude oil): A fluid, hydrocarbon-rich mixture mined from certain geological formations.

phenotype: The expressed characteristics of an individual organism, due to genetic and environmental influences on the expression of its specific genetic information. See also genotype.

phenotypic plasticity: The variable expression of genetic information of an individual, depending on environmental influences during development.

photoautotroph: Plants and algae that use sunlight to drive their fixation of energy through photosynthesis. See also chemoautotroph and photosynthesis.

photochemical air pollutants: Ozone, peroxy acetyl nitrate, and other strongly oxidizing gases that form in the atmosphere through complex reactions involving sunlight, hydrocarbons, oxides of nitrogen, and other chemicals.

photosynthesis: Autotrophic productivity that utilizes visible electromagnetic energy (such as sunlight) to drive biosynthesis.

phytoplankton: Microscopic, photosynthetic bacteria and algae that live suspended in the water of lakes and oceans.

plantation: In forestry, these are tree-farms managed for high productivity of wood fibre.

poaching: The illegal harvesting of wild life (plants or animals).

point source: A location where large quantities of pollutants are emitted into the environment, such as a smokestack or sewer outfall.

political ecology: This integrates the concerns of ecology and political economy to consider the dynamic tensions between natural and anthropogenic change, and also the consideration of damage from both natural and anthropogenic perspectives; the latter includes the broad range of concerns from individual people to all of society.

pollution: The exposure of organisms to chemicals or energy in quantities that exceed their tolerance, causing toxicity or other ecological damages. Compare with contamination.

population: In ecology, this refers to individuals of the same species that occur together in time and space.

positive analysis: A study of how things are.

positive externality: A benefit that accrues to someone who did not agree to the activity that caused the benefit.

potential energy: The stored ability to perform work, capable of being transformed into electromagnetic or kinetic energies. Potential energy is associated with gravity, chemicals, compressed gases, electrical potential, magnetism, and the nuclear structure of matter.

post-traumatic stress disorder: PTSD – a psychological condition affecting people who have suffered severe emotional trauma as a result of an experience such as combat, crime, or natural disaster, and causing sleep disturbances, flashbacks, anxiety, tiredness, and depression.

potentially renewable natural resource: An alternate phrase for renewable natural resource, highlighting the fact that these can be overexploited, and thereby treated as if they were nonrenewable resources. See also renewable resource.

ppb (part per billion): A unit of concentration, equivalent to 1 microgram per kilogram (µg/kg), or in aqueous solution, 1 µg per litre (µg/L).

ppm (part per million): A unit of concentration, equivalent to 1 milligram per kilogram (mg/kg), or in aqueous solution, 1 mg per litre (mg/L).

prairie: Grassland ecosystems occurring in temperate regions.

precautionary principle: An approach to environmental management, adopted by many countries at the 1992 Earth Summit, which essentially states that scientific uncertainty is not a sufficient reason to postpone control measures when there is a threat of harm to human health or the environment.

precipitation: Deposition of water from the atmosphere as liquid rain, or as solid snow or hail.

precision: The degree of repeatability of a measurement or observation. Compare with accuracy.

present discounted value: The value of something in present-day (rather than future) terms.

prevailing wind: Wind that blows in a dominant direction.

primary consumer: A herbivore, or a heterotrophic organism that feeds on plants or algae.

primary pollutants: Chemicals that are emitted into the environment. Compare with secondary pollutants.

primary producer: An autotrophic organism. Autotrophs are the biological foundation of ecological productivity. See also primary production.

primary production: Productivity by autotrophic organisms, such as plants or algae. Often measured as biomass accumulated over a unit of time, or sometimes by the amount of carbon fixed.

primary sewage treatment: The initial stage of sewage treatment, usually involving the filtering of larger particles from the sewage wastes, settling of suspended solids, and sometimes chlorination to kill pathogens.

Principle of Limiting Factors: A theory stating that ecological productivity (and some other functions) is controlled by whichever environmental factor is present in least supply relative to the demand.

production: An ecological term related to the total yield of biomass from some area or volume of habitat.

production life: See life index.

productivity: An ecological term for production standardized per unit area and time.

prokaryote: Microorganisms without an organized nucleus containing their genetic material. Compare with eukaryote.

protected area (reserve): Parks, ecological reserves, and other tracts set aside from intense development to conserve their natural ecological values. See also greater protected area. 

public good: A good with two features: (i) it has a benefit that does not diminish with the number of people enjoying it, and (ii) no one can be excluded from consuming it.

r-selected: Refers to organisms that produce relatively large numbers of small offspring. Little parental investment is made in each offspring, but having large numbers of progeny helps ensure that some will establish and survive. Compare with K-selected.

radiatively active gases (RAGs): Atmospheric gases that efficiently absorb infrared radiation and then dissipate some of the thermal energy gain by reradiation.

rapidly developing countries: Countries with a quickly growing economic infrastructure and a rapidly increasing average per-capita income. See also high-income and low-income countries and compare with developed countries and less-developed countries.

reclamation: Actions undertaken to establish a self-maintaining ecosystem on degraded land, as when a disused industrial site is converted into a permanent cover of vegetation, such as a pasture. Compare with restoration and remediation.

recycling: The processing of discarded materials into useful products.

relative humidity: The atmospheric concentration of water, expressed as a percentage of the saturation value for that temperature.

remediation: Specific actions undertaken to deal with particular problems of environmental quality, such as the liming of acidic lakes and rivers to decrease their ecological damage. Compare with restoration and reclamation.

remote responsibilities: An ethical extension of systems literacy and the principle of connectivity: we are linked to peoples and places remote from us through the web of global industrial production and commerce, and thus have responsibility toward them.

renewable resource (renewable natural resource): These can regenerate after harvesting, and potentially can be exploited forever. Examples are fresh water, trees, agricultural plants and livestock, and hunted animals. Compare with nonrenewable resources.

replacement fertility rate: The fertility rate that results in the numbers of progeny replacing their parents, with no change in size of the equilibrium population.

replication: The biochemical process occurring prior to cellular division, by which information encoded in DNA is copied to produce additional DNA with the same information.

reserve: (1) Known quantities of resources that can be economically recovered from the environment. (2) An alternative word for a protected area. See protected area.

residence time: (1) The time required for the disappearance of an initial amount; (2) The length of time that a stressor or other environmental influence remains active.

residue: Lingering concentrations of pesticides and certain other chemicals in organisms and the environment.

resilience: The ability of a system to recover from disturbance.

resistance: The ability of a population or community to avoid displacement from some stage of ecological development as a result of disturbance or an intensification of environmental stress. Changes occur after thresholds of resistance to environmental stressors are exceeded.

resource recovery facility: See waste-to-energy facility.

respiration: Physiological processes needed to maintain organisms alive and healthy.

response: In ecotoxicology, this refers to biological or ecological changes caused by exposure to an environmental stressor.

restoration: Establishment of a self-maintaining facsimile of a natural ecosystem on degraded land, as when abandoned farmland is converted back to a native prairie or forest. Compare with reclamation and remediation.

restoration ecology: Activities undertaken by ecologists to repair ecological damage, such as establishing vegetation on degraded habitat, increasing the populations of endangered species, and decreasing the area of threatened ecosystems.

reuse: Finding another use for discarded materials, usually with relatively little modification. 

revealed preference: Valuation tools that use behaviors such as job choice, housing choice, and recreational site choice to reveal information about the values people have for features of the environment.

risk: See environmental risks.

risk assessment: See environmental risk assessment.

RNA: The biochemical ribonucleic acid, which is important in translation of the genetic information of DNA into the synthesis of proteins. RNA also stores the genetic information of some viruses.

ruderal: Short-lived but highly fecund plants characteristic of frequently disturbed environments with abundant resources.

run-of-the-river: A hydroelectric development that directly harnesses the flow of a river to drive turbines, without creating a substantial impoundment for water storage.

salinization: The buildup of soluble salts in the soil surface, an important agricultural problem in drier regions.

sanitary landfill: A facility where municipal solid waste is dumped, compacted by heavy machines, and covered with a layer of clean dirt at the end of the day. Some have systems to contain and collect liquid effluent, known as leachate.

science: The systematic and quantitative study of the character and behaviour of the physical and biological world.

scientific creationist: A creationist who attempts to explain some of the discrepancies between his or her beliefs (which are based on a literal interpretation of Genesis) and scientific understanding of the origin and evolution of life. See also creationist.

scientific method: This begins with the identification of a question involving the structure or function of the natural world, usually using inductive logic. The question is interpreted in terms of a theory, and hypotheses are formulated and tested by experiments and observations of nature.

scrubbing: See flue-gas desulphurization.

seascape: A spatial integration of ecological communities over a large marine area.

second law of thermodynamics: A physical principle stating that transformations of energy can occur spontaneously only under conditions in which there is an increase in the entropy (or randomness) of the universe. See also first law of thermodynamics and entropy.

secondary consumer: A carnivore that feeds on primary consumers (or herbivores).

secondary pollutants: Pollutants that are not emitted, but form in the environment by chemical reactions involving emitted chemicals. Compare with primary pollutants.

secondary sewage treatment: Treatment applied to the effluent of primary sewage treatment, usually involving the use of a biological technology to aerobically decompose organic wastes in an engineered environment. The resulting sludge can be used as a soil conditioner, incinerated, or dumped into a landfill. See also primary sewage treatment.

sedimentary rock: Rock formed from precipitated minerals such as calcite, or from lithified particles eroded from other rocks such as sandstone, shale, and conglomerates.

sedimentation: A process by which mass eroded from elsewhere settles to the bottom of rivers, lakes, or an ocean.

seismic sea wave: See tsunami.

selection harvesting: Harvesting of only some trees from a stand, leaving others behind and the forest substantially intact.

sensitivity analysis: Evaluation of how sensitive the results of an analysis are to changes in assumptions used in the analysis.

sewage treatment: The use of physical filters, chemical treatment, and/or biological treatment to reduce pathogens, organic matter, and nutrients in waste waters containing sewage.

shifting cultivation: An agricultural system in which trees are felled, the woody debris burned, and the land used to grow mixed crops for several years.

significant figures: The number of digits used when reporting data from analyses or calculations.

silvicultural management: The application of practices that increase tree productivity in a managed forest, such as planting seedlings, thinning trees, or applying herbicides to reduce the abundance of weeds.

silviculture: The branch of forestry concerned with the care and tending of trees.

site capability (site quality): The potential of land to sustain the productivity of agricultural crops.

slash-and-burn: An agricultural system that results in a permanent conversion of a forest into crop production, involving cutting and burning the forest followed by continuous use of the land for crops.

slope: The angle of inclination of land, measured in degrees (0° implies a horizontal surface, while 90° is vertical).

SLOSS: An acronym, for single large or several small, in reference to choices in the design of protected areas.

sludge: A solid or semi-solid precipitate that settles from polluted water during treatment; sludge is produced during the treatment of sewage and also in pulp mills and some other industrial facilities. It may be disposed of in a landfill, but if organic, can be used as a beneficial soil amendment.

smog: An event of ground-level air pollution.

snag: A standing dead tree.

social justice: A worldview that calls for equality of consideration for all members of a society, regardless of colour, race, socio-economic class, gender, age, or sexual preference. See also ecological justice.

socio-cultural evolution: See cultural evolution.

socio-economic impact assessment: A process used to identify and evaluate the potential consequences of proposed actions or policies for sociological, economic, and related values. See also environmental impact assessment.

soil: A complex mixture of fragmented rock, organic matter, moisture, gases, and living organisms that covers almost all of Earth’s terrestrial landscapes.

soil profile: The vertical stratification of soil on the basis of colour, texture, and chemical qualities.

solar energy: Electromagnetic energy radiated by the sun.

solar system: The sun, its nine orbiting planets, miscellaneous comets, meteors, and other local materials.

solid wastes: Extremely variable municipal wastes that include discarded food, garden discards, newspapers, bottles, cans, construction debris, old cars, and disused furniture.

spaceship Earth: An image of Earth as viewed from space, which illustrates the fact that, except for sunlight, resources needed by humans are present only on that planet.

spaceship world view: This focuses on sustaining only those resources needed by humans and their economy, and it assumes that humans can exert a great degree of control over natural processes and can pilot “spaceship Earth.” See also frontier world view and sustainability world view.

special concern: Refers to a species that is not currently threatened but is at risk of becoming so for various reasons.

species: An aggregation of individuals and populations that can potentially interbreed and produce fertile offspring, and is reproductively isolated from other such groups.

speciesism: Discrimination (by humans) against other species purely on the basis that they are not human, especially as manifested by cruelty to or exploitation of animals, or merely by a lack of consideration of their interests.

species richness: The number of species in some area or place.

state-of-the-environment reporting: A governmental, corporate, or NGO function that involves public reporting on environmental conditions.

stated preference: Valuation tools that use survey responses to hypothetical questions rather than data on actual choices.

strategic weapon: Large explosive-yield weapons that are designed to be delivered by a missile or airplane over a distance of thousands of kilometres. Compare with tactical weapon.

stratosphere: The upper atmosphere, extending above the. from 8-17 km to as high as about 50 km. See also troposphere.

stress-tolerator: Long-lived plants adapted to habitats that are marginal in terms of climate, moisture, or nutrient supply, but are infrequently disturbed and therefore stable, such as tundra and desert.

stressor: An environmental factor that constrains the development and productivity of organisms or ecosystems.

succession: A process of community- level recovery following disturbance.

surface flow: Water that moves over the surface of the ground.

surface water: Water that occurs in glaciers, lakes, ponds, rivers, streams, and other surface bodies of water.

sustainability world view: This acknowledges that humans must have access to vital resources, but it asserts that the exploitation of resources should be governed by appropriate ecological, aesthetic, and moral values, and should not deplete the necessary resources. See also frontier world view and spaceship world view.

sustainable development: Refers to progress toward an economic system that uses natural resources in ways that do not deplete their stocks or compromise their availability to future generations.

sustainable economic system (sustainable economy): An economic system that can be maintained over time without any net consumption of natural resources.

swamp: A forested wetland, flooded seasonally or permanently.

symbiosis: An intimate relationship between different species. See also mutualism.

synchronic: A synchronic view is concerned with its characteristics at a single point in time.

synecology: The study of relationships among species within communities. Compare with autecology.

system: A group or combination of regularly interacting and interdependent elements, which form a collective entity, but one that is more than the sum of its constituents. See also ecosystem.

systems literacy: An educational philosophy that emphasizes a student’s competence in a wide variety of disciplines, so that he or she might better understand the operations of those complex systems, both human and natural, that underpin sustainability.

tactical weapon: Smaller, numerous weapons that are intended for use in a local battlefield, and are delivered by smaller missiles, artillery, aircraft, or torpedoes. Compare with strategic weapon.

taiga: See boreal forest. 

technology standard: A regulation specifying what kind of technology agents must or must not use in their activities.

tectonic force: Force associated with crustal movements and related geological processes that cause structural deformations of rocks and minerals.

temperate deciduous forest: A forest occurring in relatively moist, temperate climates with short and moderately cold winters and warm summers, and usually composed of a mixture of angiosperm tree species.

temperate grassland: Grass-dominated ecosystems occurring in temperate regions with an annual precipitation of 25–60 cm per year; sufficient to prevent desert from developing but insufficient to support forest.

temperate rainforest: A forest developing in a temperate climate in which winters are mild and precipitation is abundant year-round. Because wildfire is rare, old-growth forests may be common.

temperature inversion: See atmospheric inversion.

teratogen: A chemical or physical agent that induces a developmental abnormality (i.e., a birth defect) in an embryo or fetus.

tertiary sewage treatment: Treatment applied to the effluent of secondary sewage treatment, usually involving a system to remove phosphorus and/or nitrogen from waste waters. See also primary sewage treatment and secondary sewage treatment.

theory: A general term that refers to a set of scientific laws, rules, and explanations supported by a large body of experimental and observational evidence, all leading to robust, internally consistent conclusions.

thermal pollution: An increase in environmental temperature sufficient to result in ecological change.

thermosphere: The layer of the atmosphere extending beyond the mesosphere to 450 km or more above the surface of the Earth. See also mesosphere.

threatened: In Canada, this refers to any indigenous taxa likely to become endangered (in Canada) if factors affecting their vulnerability are not reversed.

tidal energy: Energy that develops in oceanic surface waters because of the gravitational attraction between Earth and the Moon, and can potentially be used to generate electricity.

tilth: The physical structure of soil, closely associated with the concentration of humified organic matter. Tilth is important in water- and nutrient-holding capacity of soil, and is generally beneficial to plant growth.

tipping point: The critical moment of nonlinear change whereby a system changes suddenly from one state to another.

tolerance: In ecotoxicology, this refers to a genetically based ability of organisms or species to not suffer toxicity when exposed to chemicals or other stressors.

total concentration: The concentrations of metals in soil, sediment, rocks, or water, as determined after dissolving samples in a strongly acidic solution. Compare with available concentration.

total energy production: The use of commercial energy plus traditional fuels in an economy. See also traditional fuels.

total-war economy: An economy that is wholly dedicated to supporting a war effort.

toxic waste: Waste that is poisonous to humans, animals, or plants. See also hazardous waste.

toxicology: The science of the study of poisons, including their chemical nature and their effects on the physiology of organisms. Compare with environmental toxicology and ecotoxicology. 

tradable permits: A policy in which the total amount of an activity is limited, but agents can trade the rights to engage in that activity (permits).

traditional fuels: The non-commercial use of wood, charcoal, animal dung, and other biomass fuels for subsistence purposes, primarily for cooking food and heating homes. See also total energy production and commercial energy production.

transcription: A biochemical process by which the information of double-stranded DNA is encoded on complementary single strands of RNA, which are used to synthesize specific proteins.

translation: A biochemical process occurring on organelles known as ribosomes, in which information encoded in messenger RNA is used to synthesize particular proteins.

transpiration: The evaporation of water from plants. Compare with evapotranspiration.

travel cost analysis: A revealed preference tool that estimates the values of natural resource amenities by analyzing data on recreational site characteristics and people’s visitation patterns and travel costs.

trophic structure: The organization of productivity in an ecosystem, including the roles of autotrophs, herbivores, carnivores, and detritivores.

troposphere: The lower atmosphere, extending to 8–17 km.

tsunami: A fast-moving, sea-wave caused by an undersea earthquakes, which if large can cause enormous destruction of low-lying coastal places.

tundra: A treeless biome occurring in environments with long, cold winters and short, cool growing seasons.

urban agglomeration: See megacity

urban forest: Urban areas having a substantial density and biomass of trees, although often most are non-native species.

urban planning: An active process of designing better ways of organizing the structure and function of cities, including an orderly siting of land uses and activities.

urban sprawl: Any environment characterized by (1) a population widely dispersed in low density residential development; (2) rigid separation of homes, shops, and workplaces; (3) a lack of distinct, thriving activity centers, such as strong downtowns or suburban town centers; and (4) a network of roads marked by large block size and poor access from one place to another) has been found to correlate with increased body mass index.

urbanization: The development of cities and towns on formerly agricultural or natural lands.

use values: Benefits associated with direct interaction with nature and the environment.

utilitarian value: The usefulness of a thing or function to humans.

Valuation: The process of estimating a dollar value for an amenity or a disamentity.

value added: The increased value of something as a result of manufacturing or some other improvement.

value of a statistical life: A statistical concept that can be used as the value of reducing the number of deaths in a population by one.

valued ecosystem components (VECs): In environmental impact assessment, these are components of ecosystems perceived to be important to society as economically important resources, as rare or endangered species or communities, or for their cultural or aesthetic significance.

variable: A changeable factor believed to influence a natural phenomenon of interest or that can be manipulated during an experiment.

vascular plant: Relatively complex plants with specialized, tube-like vascular tissues in their stems for conducting water and nutrients.

VECs: See valued ecosystem components.

vector: Species of insects and ticks that transmit pathogens from alternate hosts to people or animals.

vertebrate: Animals with an internal skeleton, and in particular a backbone.

virgin field: In epidemiology, this is a population that is hypersensitive to one or more infectious diseases to which it has not been previously exposed.

volatile organic compounds: Organic compounds that evaporate to the atmosphere at typical environmental temperatures, so they are present in gaseous or vapour forms.

volcano: An opening in Earth’s crust from which magmic materials, such as lava, rock fragments, and gases, are ejected into the atmosphere or oceanic waters.

war: A period of organized deadly conflict between human societies, countries, or another defined group.

waste: Any discarded materials. See also hazardous waste and toxic waste.

waste management: The handling of discarded materials using various methods. See also dumping, incineration, recycling, composting, reuse, and waste reduction.

waste prevention: See waste reduction.

waste reduction: Practices intended to reduce the amount of waste that must be disposed of. Also known as waste prevention.

waste-to-energy facility: An incinerator that burns organic waste and uses the heat generated to produce commercial energy.

water cycle: See hydrologic cycle.

watershed: An area of land from which surface water and groundwater flow into a stream, river, or lake.

wave energy: The kinetic energy of oceanic waves, which can be harnessed using specially designed buoys to generate electricity.

weather: The short-term, day-to-day or instantaneous meteorological conditions at a place or region. Compare with climate.

weathering: Physical and chemical processes by which rocks and minerals are broken down by such environmental agents as rain, wind, temperature changes, and biological influences.

weed: An unwanted plant that interferes with some human purpose.

welfare: Broadly defined, welfare is well-being.

wet deposition: Atmospheric inputs of chemicals with rain and snow. Compare with dry deposition.

wetland: An ecosystem that develops in wet places and is intermediate between aquatic and terrestrial ecosystems. See also bog, fen, marsh, and swamp.

whole-lake experiment: The experimental manipulation of one or more environmental factors in an entire lake.

willingness to accept: The amount of money you would have to pay someone to compensate them for a deleterious change. 

willingness to pay: The amount of money someone is willing to pay for something good.

wind: An air mass moving in Earth’s atmosphere.

wind energy: The kinetic energy of moving air masses, which can be tapped and utilized in various ways, including the generation of electricity.

work: In physics, work is defined as the result of a force being applied over a distance.

working hypothesis: A hypothesis being tested in a scientific experiment or another kind of research. See also hypothesis and null hypothesis.

zero population growth (ZPG): When the birth rate plus immigration equal the death rate plus emigration.

zooplankton: Tiny animals that occur in the water column of lakes and oceans.