s

ecological dictionary

S

Salinity

The amount of salt in the water or ground.

Scavenger

Animals that feed on other animals that are already dead, e.g. vultures. Fungi and bacteria that grow on dead or decomposing organic matter, such as feces or the remains of dead animals are called decomposers. (See also Decomposers.)

Secondary Forest

A forests that appears after a brief fire or agricultural use of the land.

Sedimentation

The process by which particles (called sediment) in a liquid settle to the bottom under the action of gravity.

In the environment, rivers carry sediment which is washed into them. Rivers carry 24.000 million tons of sediments to the sea each year. From this total it is believed that only 9.300 million tons are of natural origin: the remainder – some 14.700 million tons – is produced by human activities.

In China, the three main rivers of Sicuani carry a natural load of 250 million tons, sufficient to cover an area of 1.600 square kilometers with a layer of 5 centimeters of vegetable matter.

In Haiti the dam of Peligre, in the river Artibonite, was built to last 50 years. The excess of sedimentation from the river threatens the long-term operation of the dam which may be rendered useless after only 30 years of use.

Excessive sedimentation can also cause floods. The problem is worse, generally in those areas where dikes have been built to control them.

Silviculture

Care and cultivation of trees and forests or jungles. It includes seeding, conservation, treatment and protection.

Social hierarchy

Levels of authority among animals.

Soil profile

The vertical cut of the soil, where you can see different layers of the earth which have distinct colors and thicknesses. In some layers there are rocks, roots and worms.

Solar energy

Energy transmitted from the sun and gathered for human needs. The amount of energy we could get from the sun each year is 15 times greater than the total consumption of energy on the entire earth. The challenge is to capture and take advantage of this rich energy source. More widespread use of solar energy would decrease the environmental contamination caused by traditional, carbon-based energy forms. To obtain this source of energy, solar panels and capturers are utilized. These require lots of space and areas with high levels of sunshine.

Stabilizers

Chemicals that are added to food products to keep the ingredients in an unchanging state.

Stratification

A horizontal formation of layers. Often used to describe sediments and rock formations.

Sulfate

A salt or ester of sulfuric acid.

Sulfide

A compound containing a single sulfur atom, e.g. hydrogen sulfide, zinc sulfide.

Sulla/Sweetvetch

Herbaceous plant which is cultivated like fodder.

Symbiosis

See “mutualism.”

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