Glossary of Environmental Science - C

C

• C3 & C4 plants – C4 plants comprise about 5% of all plants, are most abundant in hot and arid conditions, and include crops like sugar cane and soybeans. During photosynthesis they form molecules with 4-carbon atoms and saturate at the given level of CO₂. C3 plants, the other 95%, photosynthesise to form 3 carbon molecules and increase photosynthesis with as CO₂ levels increase.
• calorie – a basic measure of energy that has been replaced by the SI unit the joule; in physics it approximates the energy needed to increase the temperature of 1 gram of water by 1 °C which is about 4.184 joules. The Calories in food ratings (spelled with a capital C) and nutrition are ‘big C’ Calories or kcal.
• calorific value – the energy content of a fuel measured as the heat released on complete combustion.
• cancer – a group of diseases in which cells are aggressive (grow and divide without respect to normal limits), invasive (invade and destroy adjacent tissues), and sometimes metastatic (spread to other locations in the body).
• capillary action (wicking) – water drawn through a medium by surface tension.
• car pooling – giving people lifts to help reduce emissions and traffic.
• carbon budget – a measure of carbon inputs and outputs for a particular activity.
• carbon credit – a market-driven way of reducing the impact of greenhouse gas emissions; it allows an agent to benefit financially from an emission reduction. There are two forms of carbon credit, those that are part of national and international trade and those that are purchased by individuals. Internationally, to achieve Kyoto Protocol objectives, ‘caps’ (limits) on participating country’s emissions are established. To meet these limits countries, in turn, set ‘caps’ (allowances or credits: 1 convertible and transferable credit = 1 metric tonne of CO₂-e emissions) for operators. Operators that meet the agreed ‘caps’ can then sell unused credits to operators who exceed ‘caps’. Operators can then choose the most cost-effective way of reducing emissions. Individual carbon credits would operate in a similar way cf. carbon offset.
• carbon cycle – the biogeochemical cycle by which carbon is exchanged between the biosphere, geosphere, hydrosphere, and atmosphere of the Earth.
• Carbon Dioxide Equivalent (CO₂e ) – the unit used to measure the impacts of releasing (or avoiding the release of) the seven different greenhouse gases; it is obtained by multiplying the mass of the greenhouse gas by its global warming potential. For example, this would be 21 for methane and 310 for nitrous oxide.
• carbon dioxide – a gas with the chemical formula CO₂; the most abundant greenhouse gas emitted from fossil fuels.
• carbon equivalent (C-e) – obtained by multiplying the CO₂-e by the factor 12/44.
• carbon footprint – a measure of the carbon emissions that are emitted over the full life cycle of a product or service and usually expressed as grams of CO₂-e.
• carbon labelling – use of product labels that display greenhouse emissions associated with goods (www.carbontrustcertification.com for product carbon footprint methodology).
• carbon neutral – activities where net carbon inputs and outputs are the same. For example, assuming a constant amount of vegetation on the planet, burning wood will add carbon to the atmosphere in the short term but this carbon will cycle back into new plant growth.
• carbon pool – a storage reservoir of carbon.
• carbon sink – any carbon storage system that causes a net removal of greenhouse gases from the atmosphere.
• carbon source – opposite of carbon sink; a net source of carbon for the atmosphere.
• carbon stocks – the quantity of carbon held within a carbon pool at a specified time.
• carbon taxes – a surcharge on fossil fuels that aims to reduce carbon dioxide emissions.
• carcinogen – a substance, radionuclide or radiation that is an agent directly involved in the promotion of cancer or in the facilitation of its propagation.
• carrying capacity – the maximum population that an ecosystem can sustain cf. biocapacity.
• catchment area – the area that is the source of water for a water supply whether a dam or rainwater tank.
• cell – (biology) the structural and functional unit of all known living organisms and is the smallest unit of an organism that is classified as living
• CFC – chlorofluorocarbon. CFCs are potent greenhouse gases which are not regulated by the Kyoto Protocol since they are covered by the Montreal Protocol.
• chlorinated hydrocarbon – see organochloride
• chlorofluorocarbons – one of the more widely known family of haloalkanes.
• circular metabolism – a system in which wastes, especially water and materials, are reused and recycled cf. linear metabolism.
• Class A pan – (water management) an open pan used as a standard for measuring water evaporation.
• cleaner production – the continual effort to prevent pollution, reduce the use of energy, water and material resources and minimise waste – all without reducing production capacity.
• clearcutting – a forestry or logging practice in which most or all trees in a forest sector are felled.
• climate change – a change in weather over time and/or region; usually relating to changes in temperature, wind patterns and rainfall; although may be natural or anthropogenic, common discourse carries the assumption that climate change is anthropogenic.
• climate – the general variations of weather in a region over long periods of time; the "average weather" cf. weather.
• cogeneration – the simultaneous production of electricity and useful heat from the combustion of the same fuel source.
• cohousing – clusters of houses having shared dining halls and other spaces, encouraging stronger social ties while reducing the material and energy needs of the community.
• coir – fibre of the coconut.
• commercial and industrial waste – (waste management) solid waste generated by the business sector as well as that created by State and Federal government, schools and tertiary institutions. Does not include that from the construction and demolition industry.
• commingled materials – (waste management) materials mixed together, such as plastic bottles, glass, and metal containers. Commingled recyclable materials require sorting after collection before they can be recycled.
• comparative risk assessment – a methodology which uses science, policy, economic analysis and stakeholder participation to identify and address areas of greatest environmental risk; a method for assessing environmental management priorities. The US EPA (www.epa.gov/seahome/comprisk.html) offers free software which contains the history and methodology of comparative risk, as well as many case studies.
• compensation point – the point where the amount of energy produced by photosynthesis equals the amount of energy released by respiration.
• compost – the aerobically decomposed remnants of organic matter.
• composting – the biological decomposition of organic materials in the presence of oxygen that yields carbon dioxide, heat, and stabilised organic residues that may be used as a soil additive.
• confined aquifer – aquifers that have the water table above their upper boundary and are typically found below unconfined aquifers.
• conspicuous consumption – the lavish spending on goods and services that are acquired mainly for the purpose of displaying income or wealth rather than to satisfy basic needs of the consumer.
• construction and demolition waste – (waste management) includes waste from residential, civil, and commercial construction and demolition activities, such as fill material (e.g. soil), asphalt, bricks and timber. C&D waste excludes construction waste which is included in the municipal waste stream. C&D waste does not generally include waste from the commercial and industrial waste stream.
• consumer democracy – using your economic capacity to promote your values.
• consumer – organism, human being, or industry that maintains itself by transforming a high-quality energy source into a lower one cf. Producer, primary production.
• consumption (ecology) – the use of resources by a living system, the inflow and degradation of energy that is used for system activity.
• consumption (economics) – part of disposable income (income after taxes paid and payments received) that is not saved, essentially the goods and services used by households; this includes purchased commodities at the household level (such as food, clothing, and utilities), the goods and services paid for by government (such as defence, education, social services and health care), and the resources consumed by businesses to increase their assets (such as business equipment and housing).
• contour ploughing (contour farming) – the farming practice of plowing across a slope following its contours. The rows formed have the effect of slowing water run-off during rainstorms so that the soil is not washed away and allows the water to percolate into the soil.
• controlled burning – a technique sometimes used in forest management, farming, prairie restoration or greenhouse gas abatement.
• Convention on the International Trade in Endangered Species (CITES) – International agreement among 167 governments aiming to ensure that cross-border trade in wild animals and plants does not threaten their survival. The species covered by CITES are listed in three Appendices, according to the degree of protection they need (see: http://www.cites.org)
• Corporate Social Responsibility – integration of social and environmental policies into day-to-day corporate business.
• covenants – formal agreements or contracts, often between government and industry sectors. The national packaging covenant and sustainability covenants are examples of voluntary covenants with a regulatory underpinning. Land covenants protect land for wildlife into the future.
• crop coefficient (Kc) – (water management) a variable used to calculate the evapotranspiration of a plant crop based on that of a reference crop.
• crop evapotranspiration (ETc) – (water management) is the crop water use – the daily water withdrawal.
• crop rotation (crop sequencing) – the practice of growing a series of dissimilar types of crops in the same space in sequential seasons for various benefits such as to avoid the build up of pathogens and pests that often occurs when one species is continuously cropped.
• crude oil – naturally occurring mixture of hydrocarbons under normal temperature and pressure.
• cullet – crushed glass that is suitable for recycling by glass manufacturers.
• cultural eutrophication - the process that speeds up natural eutrophication because of human activity.
• cultural services – the non-material benefits of ecosystems including refreshment, spiritual enrichment, knowledge, artistic satisfaction.
• culture jamming – altering existing mass media to criticise itself (e.g. defacing advertisements with an alternative message). Public activism opposing commercialism as little more than propaganda for established interests, and the attempt to find alternative expression.
• culvert – drain that passes under a road or pathway, may be a pipe or other conduit.
• cut and fill – removing earth from one place to another, usually mechanically.
• cyanobacteria (Cyanophyta or blue-green algae) – a phylum of bacteria that obtain their energy through photosynthesis.
• cyclone – intense low pressure weather systems; mid-latitude cyclones are atmospheric circulations that rotate clockwise in the Southern Hemisphere and anti-clockwise in the Northern Hemisphere and are generally associated with stronger winds, unsettled conditions, cloudiness and rainfall. Tropical cyclones (which are called hurricanes in the Northern Hemisphere) cause storm surges in coastal areas.