ng matter in a given area
or volume.

Carbon cycle - the term used to describe the exchange of carbon (in
various forms, e.g., as carbon dioxide) between the atmosphere, ocean,
terrestrial biosphere, and geological deposits.

Catchments - assemblages used to capture and retain rainwater and
runoff; an important water management technique in areas with limited
freshwater resources, such as Gibraltar.

DDT (dichloro-diphenyl-trichloro-ethane) - a colorless, odorless
insecticide that has toxic effects on most animals; the use of DDT was
banned in the US in 1972.

Defoliants - chemicals which cause plants to lose their leaves
artificially; often used in agricultural practices for weed control,
and may have detrimental impacts on human and ecosystem health.

Deforestation - the destruction of vast areas of forest (e.g.,
unsustainable forestry practices, agricultural and range land clearing,
and the over exploitation of wood products for use as fuel) without
planting new growth.

Desertification - the spread of desert-like conditions in arid or semi-
arid areas, due to overgrazing, loss of agriculturally productive
soils, or climate change.

Dredging - the practice of deepening an existing waterway; also, a
technique used for collecting bottom-dwelling marine organisms (e.g.,
shellfish) or harvesting coral, often causing significant destruction
of reef and ocean-floor ecosystems.

Drift-net fishing - done with a net, miles in extent, that is generally
anchored to a boat and left to float with the tide; often results in an
over harvesting and waste of large populations of non-commercial marine
species (by-catch) by its effect of "sweeping the ocean clean".

Ecosystems - ecological units comprised of complex communities of
organisms and their specific environments.

Effluents - waste materials, such as smoke, sewage, or industrial waste
which are released into the environment, subsequently polluting it.

Endangered species - a species that is threatened with extinction
either by direct hunting or habitat destruction.

Freshwater - water with very low soluble mineral content; sources
include lakes, streams, rivers, glaciers, and underground aquifers.

Greenhouse gas - a gas that "traps" infrared radiation in the lower
atmosphere causing surface warming; water vapor, carbon dioxide,
nitrous oxide, methane, hydrofluorocarbons, and ozone are the primary
greenhouse gases in the Earth's atmosphere.

Groundwater - wa