Air: A mixture of gases including nitrogen, carbon dioxide, hydrogen, oxygen, methane, water vapour, and other gases. The atmosphere is composed of air, water droplets, and various particles.

Air Pollution: A general term referring to the emission of harmful substances into the air.

Biodiversity: The degree of variety to be found in nature. Biodiversity can be found at three levels: genetic diversity-the variety of different genes to be found in a species; species diversity-the number of different species to be found in a region; and ecosystem diversity-the number of different habitat types within a region.

Carrying Capacity: The ability of an ecosystem to support life.

Chloroflurocarbons (CFCs): Synthetic, human produced molecules containing carbon, chlorine and fluorine atoms. CFCs are used as foaming agents in styrofoam or other plastic products, as refrigerants in refrigerators and air conditioners, and as cleaning agents for electronic components. CFCs are greenhouse gases and, in the upper atmosphere, can cause the destruction of ozone molecules.

Demographers: scholars who study population distribution, age structure, composition, life style, and change.

Demography: (See demographers): the science which studies the nature and structure of human populations at the local, regional, national and global level.

Developing Countries: A category which includes Low and Middle income countries. Low income countries are defined by the World Bank as having an annual per capita gross national product (GNP) of less than US$580 in 1989. Middle income countries are defined as having a per capita GNP of between US$580 and US$ 6000 in 1989.

Ecosystem: An integrated and stable association of living and non-living resources functioning within a defined physical location. An ecosystem may be as large as the entire Earth (Ecosphere) or as small as a pond or lake.

Effluents, Industrial: heavy metals or synthetic organic compounds commonly associated with pulp and paper, petrochemical, refining, metalworking, food processing, and textile production or manufacture, all of which are suspended or dissolved in water. Effluents may be released into water bodies by any of these processes.

Fossil Fuels: substances which can be burned to produce energy. Fossil fuels store energy from past photosynthetic activities of plants. They include coal, oil, and natural gas all of which are formed over long periods of time by geological processes which compress and alter decomposed plant and animal materials from the past.

Global Change: Changes in the composition and operation of the ecosphere over time are known as global changes. Global change includes gradual processes and those which may be rapid or catastrophic. Global change is naturally occurring, a result of the operation and interaction of various Earth systems over time. Global change can be influenced in scope and rate by human activities such as production of pollutants, deforestation, species destruction, and population growth.

Greenhouse Effect: Solar energy passes through the Earth's atmosphere and is received at the Earth's surface. Some of this is re-emitted as heat energy. The outgoing energy is trapped by clouds and by Greenhouse Gases (see below) resulting in a warming of the atmosphere, surface, and oceans. The Greenhouse Effect is a naturally occurring phenomenon which makes our planet livable. It can be increased by human activities or natural processes which raise the concentrations of Greenhouse Gases in the atmosphere.

Greenhouse Gases: Gases which permit solar energy to pass through the atmosphere but which trap re-radiated heat energy causing an insulating or warming effect. These include naturally occurring gases such as Carbon Dioxide, Nitrous Oxide, Methane, and Water Vapor. They also include gases made by humans, such as Chlorofluorocarbons.

Habitat: The environment in which a population or individual occurs.

Indigenous: A plant or animal which naturally occurs within a region without human intervention. Recently the term has been applied to the First Nations peoples living in various regions of the Earth prior to historical time or to contact with European explorers and settlers.

Limiting Factors: Factors which limit an ecosystem's capacity to support life. Some limiting factors include water, air, food, and shelter.

Ozone: A naturally occurring oxygen molecule with an extra oxygen atom attached. The formula for ozone is O3 as compared to O2, the oxygen gas which is a major component of the atmosphere. At the Earth's surface ozone is a significant pollutant as a component of photochemical smog. In the upper atmosphere it is an important shield from Ultra Violet radiation (UVB).

Ozone Depletion: Ozone depletion results when molecules of CFC (chloroflurocarbon) or halon gases break down under the influence of UV radiation in the upper atmosphere to release chlorine or bromine atoms which in turn attack ozone molecules resulting in the formation of regular oxygen gas (O2). One chlorine or bromine atom can destroy 100 000 ozone molecues.

Ozone Layer: A layer of higher ozone concentration found in the stratosphere (15-25 km above the Earth's surface.). This layer provides protection from Ultra Violet B radiation (UVB).

Photochemical Smog: A type of air pollution occurring at ground level or low elevations and containing major amounts of Ozone. While ozone in the upper atmosphere is a protection against UVB radiation, at ground level ozone is toxic to plant and animal life. Ozone in the photochemical smog is produced by reactions between automobile exhaust and volatile organic compounds from gasoline vapor, dry cleaning, and other industrial processes.

Recyclable: Products or materials such as paper, glass, plastic, oil, and metal which can be reprocessed for further use rather than disposed of as trash or waste.

Soil Degradation: The partial or total loss of the soil's productive capacity. Ultimately soil degradation results in desertification: the production of areas in which few or no plants can grow.

UNCED: United Nations Conference on Environment and Development. A world conference organized by the United Nations, held in Rio de Janeiro, Brazil, in June, 1992, among the nations of the world to discuss policies and strategies for sustainable development and environmental protection and conservation.

UNDP: United Nations Development Programme. A programme of the United Nations aimed at improving economic and social conditions in developing countries.