o acid
precipitation and deposition usually through precipitation; this
process disrupts ecosystem nutrient flows and may kill freshwater fish
and plants dependent on more neutral or alkaline conditions (see acid
rain).

Acid rain - characterized as containing harmful levels of sulfur
dioxide or nitrogen oxide; acid rain is damaging and potentially deadly
to the earth's fragile ecosystems; acidity is measured using the pH
scale where 7 is neutral, values greater than 7 are considered
alkaline, and values below 5.6 are considered acid precipitation; note
- a pH of 2.4 (the acidity of vinegar) has been measured in rainfall in
New England.

Aerosol - a collection of airborne particles dispersed in a gas, smoke,
or fog.

Afforestation - converting a bare or agricultural space by planting
trees and plants; reforestation involves replanting trees on areas that
have been cut or destroyed by fire.

Asbestos - a naturally occurring soft fibrous mineral commonly used in
fireproofing materials and considered to be highly carcinogenic in
particulate form.

Biodiversity - also biological diversity; the relative number of
species, diverse in form and function, at the genetic, organism,
community, and ecosystem level; loss of biodiversity reduces an
ecosystem's ability to recover from natural or man-induced disruption.

Bio-indicators - a plant or animal species whose presence, abundance,
and health reveal the general condition of its habitat.

Biomass - the total weight or volume of living 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 us