| S curve
|
| A curve that depicts logistic growth; called an S curve because of its shape.
|
|
| Safe Drinking Water Act of 1974
|
| Legislation to protect the public from the risk that toxic chemicals will contaminate drinking water supplies. Mandates regular testing of municipal water supplies.
|
|
| Safety net
|
| In a society, the availability of food and other necessities extended to people who are unable to meet their own needs for a variety of reasons.
|
|
| Salinity
|
| Amount of dissolved salts (especially sodium chloride) in a given volume of water.
|
|
| Salinization
|
| A process in which mineral salts accumulate in the soil, killing plant; occurs when soils in dry climates are irrigated profusely.
|
|
| Saltwater intrusion
|
| Movement of saltwater into freshwater aquifers in coastal areas where groundwater is withdrawn faster than it is replenished.
|
|
| Sand
|
| Mineral particles 0.2u0.2mm in diameter.
|
|
| Sanitary landfill
|
| Solid waste disposal site where garbage is dumped and covered daily with a layer of dirt to reduce odors, insects, and rats.
|
|
| Sanitary sewer
|
| Separate drainage system used to receive all the wastewater from sinks, tubs, and toilets.
|
|
| SARA (Title III)
|
| A section of the Superfund Amendments and Reauthorization Act that promulgates community Right-to-Know requirements. Also know as Emergency Planning and Community Right-to-Know Act of 1986. (See toxics release inventory)
|
|
| Saturation point
|
| The maximum concentration of water vapor the air can hold at a given temperature.
|
|
| Savanna
|
| A type of grassland typical of subtropical regions, particularly in Africa, usually dotted with trees and supported by wet and dry seasons and frequent natural fires.
|
|
| Scavenger
|
| An organism that feeds on the dead bodies of other organisms.
|
|
| Science
|
| A methodical, precise, objective way to study the natural world.
|
|
| Scientific method
|
| A systematic, precise, objective study of a problem. Generally this requires observation, hypothesis development and testing, data gathering, and interpretation.
|
|
| Scrubber
|
| Pollution control device that removes particulates and sulfur oxides from smokestacks by passing exhaust gases through a fine spray of water containing lime.
|
|
| Secondary air pollutants
|
| Air pollutants resulting from reactions for primary air pollutants while resident in the atmosphere. These include ozone, other reactive organic compounds, and sulfuric and nitric acids. (See ozone, PANs, and photochemical oxidants.)
|
|
| Secondary consumer
|
| An organism such as a fox or coyote that feeds more or less exclusively on other animals that feed on plants.
|
|
| Secondary energy source
|
| A form of energy such as electricity that must be produced from a primary energy source such as coal or radioactive material.
|
|
| Secondary pest outbreak
|
| The phenomenon of a small, and therefore harmless, population of a plant-eating insect suddenly exploding to become a serious pest problem. Often caused by the elimination of competitors through pesticide use.
|
|
| Secondary recovery technique
|
| Pumping pressurized gas, steam, or chemical-containing water into a well to squeeze more oil from a reservoir.
|
|
| Secondary standards
|
| Regulations of the 1970 Clean Air Act intended to protect materials, crops, visibility, climate, and personal comfort.
|
|
| Secondary succession
|
| Succession on a site where an existing community has been disrupted.
|
|
| Secondary treatment
|
| Bacterial decomposition of suspended particulates and dissolved organic compounds that remain after primary sewage treatment.
|
|
| Second law of efficiency
|
| Measure of the efficiency of energy use taking into account the unavoidable loss (described by the second law of thermodynamics) of energy during energy conversions. Calculated by dividing the minimum amount of energy required to perform a task by the actual amount used.
|
|
| Second law of thermodynamics
|
| States that, with each successive energy transfer or transformation in a system, less energy is available to do work.
|
|
| Second principle of ecosystem sustainability
|
| Whereby resources are supplied and wastes are disposed of by recycling all elements.
|
|
| Second-generation pesticides
|
| Synthetic organic compounds used to kill insects and other pests. Started with the use of DDT in the 1940s.
|
|
| Second World
|
| The industrialized, socialist, centrally planned economy nations of Eastern Europe and the former Soviet Union and its allies.
|
|
| Secure landfill
|
| A solid waste disposal site lined and capped with an impermeable barrier to prevent leakage or leaching. Drain tiles, sampling wells, and vent systems provide monitoring and pollution control.
|
|
| Sediment
|
| Soil particles ¡V namely, sand, silt, and clay ¡V carried by flowing water. The same material after it has been deposited. Because of different rates of settling, deposits generally are pure sand, silt, or clay.
|
|
| Sedimentary rock
|
| Deposited material that remains in place long enough or is covered with enough material to compact into stone; examples include shale, sandstone, breccia, and conglomerates.
|
|
| Sedimentation
|
| The deposition of organic materials or minerals by chemical, physical, or biological processes. Sediments can be transported from their source to their place of deposition by gravity, wind, water, or ice. If subjected to sufficient heat, pressure, or chemical reactions, sediments can solidify into sedimentary rock.
|
|
| Sediment trap
|
| A device for trapping sediment and holding it on a development or mining site.
|
|
| Seep
|
| Where groundwater seeps from the ground over some area as opposed to a spring, which is the exit as a single point.
|
|
| Selective advantage
|
| An advantage one member of a species has over others by virtue of some adaptation it has acquired.
|
|
| Selective breeding
|
| The breeding of certain individuals because they bear certain traits and the exclusion from breeding of others.
|
|
| Selective cutting
|
| Harvesting only mature trees of certain species and size; usually more expensive than clear-cutting, but it is less disruptive for wildlife and often better for forest regeneration.
|
|
| Selective pressure
|
| A fundamental mechanism of evolution. An environmental factor that causes individuals with certain traits, which are not the norm for the population, to survive and reproduce more than the rest of the population. For example, the presence of insecticides provides a selective pressure to increase pesticide resistance in the pest population.
|
|
| Septic system
|
| An on-site method of treating sewage widely used in suburban and rural areas. Requires a suitable amount of land and porous soil.
|
|
| Seriously undernourished
|
| Those who receive less than 80 percent of their minimum daily caloric requirements; are likely to suffer permanently stunted growth, mental retardation, and other social and developmental disorders.
|
|
| Sewage treatment plant
|
| Facility where human solid and liquid wastes from homes, hospitals, and industries are treated, primarily to remove organic matter, nitrates, and phosphates.
|
|
| Sex attractant
|
| A natural chemical substance (pheromone) secreted by the female of many insect species that serves to attract males for the function of mating. Sex attractants may be used in traps or for the confusion technique to aid in the control of insect pests.
|
|
| Shale oil
|
| Thick, heavy oil formed when shale is heated (retorted). Can be refined to produce fuel oil, kerosene, diesel fuel, and other petroleum products and petrochemicals.
|
|
| Shallow ecology
|
| A critical term applied to superficial environmentalists who claim to be green but are quick to compromise and who do little to bring about fundamental change. Many of those accused of being shallow ecologists counter that they are merely pragmatic, progressive reformers who prefer to work within the established social contract rather than try to overthrow it.
|
|
| Shallow pricing
|
| In cost-benefit analysis, a technique used to estimate benefits where normal economic analysis is ineffective. For example, people could be asked how much they might be willing to pay monthly to achieve some improvement in their environment.
|
|
| Shantytowns
|
| Settlements created when people move onto undeveloped lands and build their own shelter with cheap or discarded materials; some are simply illegal subdivisions where a landowner rents land without city approval; others are land invasions.
|
|
| Sheet erosion
|
| Peeling off thin layers of soil from the land surface; accomplished primarily by wind and water.
|
|
| Shelterbelts
|
| Rows of trees around cultivated fields for the purpose of reducing wind erosion.
|
|
| Shelter-wood cutting
|
| Three-step process spread out over years: (1) removal of poor-quality trees to improve growth of commercially valuable trees and allow new seedlings to become established, (2) removal of commercially valuable trees once seedlings are established, and (3) cutting remaining mature trees grown from seedlings.
|
|
| Sievert
|
| A unit of measurement of the ability of radioactive emissions to penetrate biological tissues. 1sievert = 100 rem.
|
|
| Sigmoidal curve
|
| An S-shaped curve.
|
|
| Silt
|
| Soil particles between the size of sand particles and clay particles; namely, particles 0.002 ¡V 0.2 mm in diameter.
|
|
| Siltation
|
| See sedimentation.
|
|
| Simplified ecosystem
|
| One with lowered species¡¦ diversity , usually as a result of human intervention.
|
|
| Sinkholes
|
| A large surface crater caused by the collapse of an underground channel or cavern; often triggered by groundwater withdrawal.
|
|
| Slash-and-burn agriculture
|
| The practice, commonly exercised throughout tropical regions, of cutting and burning vegetation to make room for agriculture. The process is highly destructive of soil humus and may lead to rapid degradation of soil.
|
|
| Sludge
|
| Semisolid mixture of organic and inorganic materials that settles out of wastewater at a sewage treatment plant.
|
|
| Sludge cake
|
| Treated sewage sludge that has been dewatered to make a moist solid.
|
|
| Sludge digesters
|
| Large tanks in which raw sludge ( removed from sewage) is treated through anaerobic digestion by bacteria.
|
|
| Slums
|
| Legal but inadequate multifamily tenements or rooming houses; some are custom built for rent to poor people; others are converted from some other use.
|
|
| Smart Growth
|
| A movement that addresses urban sprawl by protecting sensitive lands and directing growth to limited areas.
|
|
| Smelter
|
| A factory where ores are melted to separate impurities from the valuable minerals.
|
|
| Smog
|
| The term used to describe the combination of smoke and fog in the stagnant air of London; now often applied to photochemical pollution products or urban air pollution of any kind.
|
|
| Social Darwinism
|
| The application (or misapplication) of the theory of evolution to social behavior.
|
|
| Social ecology
|
| A socialist/humanist philosophy based on the communitarian anarchism of the Russian geographer Peter Kropotkin. It shares much with deep ecology except that it is more humanist in its outlook.
|
|
| Social justice
|
| Equitable access to resources and the benefits derived form them; a system that recognizes inalienable rights and adheres to what is fair, honest, and moral.
|
|
| Social modernization
|
| A process of sustainable development that leads developing countries through the demographic transition by promoting education, family planning, and health improvements rater than simply economic growth.
|
|
| Sociocusis
|
| Hearing loss from human activities. Contrast with presbycusis.
|
|
| Soft path
|
| A term coined by Amory Lovins to describe such practices as conservation, efficient use of energy, and renewable energy systems such as solar and wind. Characterized by high labor intensity, decentralized energy production, and small-scale technology. Contrast with hard path.
|
|
| Soft water
|
| Water with little or no calcium, magnesium, or other ions in solution that will cause soap to precipitate (form a curd that makes a ¡§ring¡¨ around the bathtub). (Contrast hard water.)
|
|
| Soil
|
| A complex mixture of weathered mineral materials from rocks, partially decomposed organic molecules, and a host of living organisms.
|
|
| Soil classes
|
| Major groupings of soil arranged like a taxonomy that define the properties of the soils of different regions.
|
|
| Soil collector
|
| Device to absorb sunlight and convert it into heat.
|
|
| Soil erosion
|
| The loss of soil caused by particles¡¦ being carried away by wind and /or water.
|
|
| Soil fertility
|
| Soil¡¦s ability to support plant growth; often refers specifically to the presence of proper amounts of nutrients. The soil¡¦s ability to fulfill all the other needs off plants is also involved.
|
|
| Soil horizons
|
| Horizontal layers that reveal a soil¡¦s history, characteristics, and usefulness.
|
|
| Soil profile
|
| A description of the different, naturally formed layers, called horizons, within a soil.
|
|
| Soil structure
|
| The composition of soil in terms of particles (sand, silt, and clay) stuck together to form clumps and aggregates, generally with considerable air spaces in between. Structure affects infiltration and aeration. It develops as organisms feed on organic matter.
|
|
| Soil texture
|
| The relative size of the mineral particles that make up the soil. Generally defined in terms of the sand, silt, and clay content.
|
|
| Solar cells
|
| See photovoltaic cells.
|
|
| Solar energy
|
| Energy derived from the Sun. includes direct solar energy (the use of sunlight directly for heating and/or production of electricity) and indirect solar energy (the use of wind, which results from the solar heating of the atmosphere, and biological materials such as wood, which result from photosynthesis).
|
|
| Solar system
|
| Group of planets revolving around a star.
|
|
| Solar-trough collectors
|
| Reflection in the shape of a parabolic trough, which reflect the sunlight onto a tube of oil at the focal point. The oil thus heated is used to boil water to drive a steam turbine.
|
|
| Solid waste
|
| The total of materials discarded as ¡§trash¡¨ and handled as solids, as opposed to those that are flushed down sewers and handled as liquids.
|
|
| Solubility
|
| The degree to which a substance will dissolve and enter into solution.
|
|
| Solution
|
| A mixture of molecules (or ions) of one material in another. Most commonly, molecules of air and/or ions of various minerals in water.
|
|
| Sonic boom
|
| A high-energy wake creating an explosive boom that trails after jets traveling faster that the speed of sound.
|
|
| Sound science
|
| The results of scientific work based on peer-reviewed research. As one of the unifying themes of this text, the basis for our understanding of how the world works and how human systems interact with it.
|
|
| Southern pine forest
|
| United States coniferous forest ecosystem characterized by a warm, moist climate.
|
|
| Spaceship earth
|
| Metaphor introduced in the 1960s to foster a greater appreciation of the finite nature of earth¡¦s resources and the ecological cycles that replenish oxygen and other important nutrients.
|
|
| Special-interest group
|
| In politics, people organized around a particular environmental issue who lobby and exert their influence on the political process to bring about changes they favor.
|
|
| Specialist
|
| Organism that has a narrow niche, usually feeding on one or a few food materials and adapted to a particular habitat.
|
|
| Specialization
|
| With reference to evolution, the phenomenon whereby species become increasingly adapted to exploit one particular niche but, thereby, are less able to exploit other niches.
|
|
| Speciation
|
| The evolutionary process whereby populations of a single species separate and, through being exposed to different forces of natural selection, gradually develop into distinct species.
|
|
| Species
|
| A population of morphologically similar organisms that can reproduce sexually among themselves but that cannot produce fertile offspring when mated with other organisms.
|
|
| Species diversity
|
| The number and relative abundance of species present in a community.
|
|
| Species recovery plan
|
| A plan for restoration of an endangered species through protection, habitat management, captive breeding, disease control, or other techniques that increase populations and encourage survival.
|
|
| Species overturn
|
| Springtime lake phenomenon that occurs when the surface ice melts and the surface water temperature warm to its greatest density at 4¢XC and then sinks, creating convection current that displaces nutrient-rich bottom waters.
|
|
| Splash erosion
|
| The compaction of soil that results when rainfall bits bare soil.
|
|
| Spontaneous abortion
|
| Loss of an embryo or fetus from the uterus not caused by surgery. Generally the result of chromosomal abnormalities. Contrast with induced abortion.
|
|
| Springs
|
| Natural exits of groundwater.
|
|
| Spring overturn
|
| Annual cycle in deep lakes in temperate climates in which surface and subsurface waters mix.
|
|
| Squatter towns
|
| Shantytowns that occupy land without owner¡¦s permission; some are highly organized movements in defiance of authorities; others grow gradually.
|
|
| SST (supersonic transport)
|
| Jet that travels faster than the speed of sound.
|
|
| Stability
|
| In ecological terms, a dynamic equilibrium among the physical and biological factors in an ecosystem or a community; relative homeostasis.
|
|
| Stable runoff
|
| The fraction of water available year-round; usually more important than total runoff when determining human uses.
|
|
| Stand Metropolitan Statistical Area (SMSA)
|
| An urbanized region with at least 100,000 inhabitants with strong economic and social ties to a central city of at least 50,000 people.
|
|
| Standing crop biomass
|
| The biomass of primary producers in an ecosystem at any given time.
|
|
| Star
|
| Spherical cloud of hot gas, such as the sun, fueled by nuclear fusion reactions in its core.
|
|
| Starvation
|
| The failure to get enough calories to meet energy needs over a prolonged period of time. It results in a wasting away of body tissues until death occurs.
|
|
| Statement on Forest Principles
|
| One of the treaties signed at the 1992 Earth Summit, where the signatory countries agreed to a number of nonbonding principles stressing sustainable management.
|
|
| Statutory law
|
| Rules passed by a state or national legislature.
|
|
| Steady-state economy
|
| Characterized by low birth and death rates, use of renewable energy sources, recycling of materials, and emphasis on durability, efficiency, and stability.
|
|
| Sterile male technique
|
| Saturating an infested area with males of the pest species that have been artificially reared and sterilized by radiation. Matings between normal females and sterile males render the eggs infertile.
|
|
| Sterilization
|
| A highly successful procedure in males and females to prevent pregnancy. In males the ducts (vas deferens) that carry sperm from the testicles are cut and tied (vasectomy); in females the Fallopian tubes, or oviducts, which transport ova from the ovary to the uterus, are cut and tied (tubal ligation) Sterilization is not to be confused with castration in males (complete removal of the gonads)
|
|
| Stewardship
|
| A philosophy that holds that humans have a unique responsibility to manage, care for, and improve nature.
|
|
| Stoma, pl. stomata
|
| Microscopic pores in leaves, mostly on the undersurface, that allow the passage of carbon dioxide and oxygen into and out of the leaf and that also permit the loss of water vapor from the leaf.
|
|
| Stomates
|
| The small openings in leaves, herbaceous stems, and fruits through which gases and water vapor pass.
|
|
| Storm drains
|
| Separate drainage systems used for collecting and draining runoff from precipitation in urban areas.
|
|
| Storm water
|
| In cities, the water that results directly from rainfall, as opposed to municipal water and sewage water piped to and from homes, offices, and so on. The extensive hard surfacing in cities creates a vast amount of stormwater runoff, which presents a significant management problem.
|
|
| Stormwater management
|
| Policies and procedures for handling stormwater in acceptable ways to reduce the problems of flooding and erosion of streambanks.
|
|
| Stormwater retention reservoirs
|
| Reservoirs designed to hold stormwater in acceptable ways to reduce the problems of flooding and streambank erosion.
|
|
| Strategic minerals
|
| Materials a country cannot produce itself but that it uses for essential materials or processes.
|
|
| Stratosphere
|
| The zone in the atmosphere extending from the tropopause to about 50km (30mi) above the earth¡¦s surface; temperatures are stable or rise slightly with altitude; has very little water vapor but is rich in ozone.
|
|
| Streambank erosion
|
| Washing away of soil from banks of established streams, creeks, or rivers, often as a result of the removal of trees and brush along streambanks or cattle damage to the banks.
|
|
| Streambed aggradation
|
| Deposition of sediment in streams or rivers, thereby reducing their reducing their water-carrying capacity.
|
|
| Streambed channelization
|
| An ecologically unsound way of reducing flooding by deppening and straightening of streams, accompanied by removal of trees and other vegetation along the banks.
|
|
| Stress
|
| Physical, chemical, or emotional factors that place a strain on an animal. Plants also experience physiological stress under adverse environmental conditions.
|
|
| Stress-related disease
|
| See stress shock.
|
|
| Stress shock
|
| A loose set of physical, psychological, and/or behavioral changes thought to result from the stress of excess competition and extreme closeness to other members of the same species.
|
|
| Strip cropping
|
| The practice of growing crops in strips alternating with grass (hay) at right angles to prevailing winds or slopes in order to reduce erosion.
|
|
| Strip-cutting
|
| Harvesting trees in strips narrow enough to minimize edge effects and to allow natural regeneration of the forest.
|
|
| Strip-farming
|
| Planting different kinds of crops in alternating strips along land contours; when one crop is harvested, the other crop remains to protect the soil and prevent water from running straight down a hill.
|
|
| Strip-mining
|
| Removing surface layers over coal seams using giant, earth-moving equipment; creates a huge open-pit from which coal is scooped by enormous surface-operated machines and transported by trucks; an alternative to deep mines.
|
|
| Structure (In ecological terms)
|
| Patterns of organization, both spatial and functional, in a community.
|
|
| Subduction
|
| In plate tectonics, where an oceanic plate slides under a continental plate.
|
|
| Sublimation
|
| The process by which water can move between solid and gaseous states without ever becoming liquid.
|
|
| Submerged aquatic vegetation (SAV)
|
| Aquatic plants rooted in bottom sediments growing under water that depend on light¡¦s penetration through the water for photosynthesis.
|
|
| Subsidence
|
| A setting of the ground surface caused by the collapse of porous formations that result from withdrawal of large amounts of groundwater, oil, or other underground materials.
|
|
| Subsoil
|
| In a natural situation, the soil beneath topsoil. In contrast to topsoil, subsoil is compacted and has little or no humus or other organic material, living or dead. In many cases, topsoil has been lost or destroyed as a result of erosion or development and subsoil is at the surface.
|
|
| Subsoil
|
| A layer of soil beneath the topsoil that has lower organic content and higher concentrations of fine mineral particles; often contains soluble compounds and clay particles carried down by percolating water.
|
|
| Succession
|
| The gradual, or sometimes rapid, change in the species that occupy a given area, with some species invading and becoming more numerous while others decline in population and disappear. Succession is caused by a change in one or more abiotic or biotic factors that benefits some species at the expense of others. Primary succession: the gradual establishment, through a series of stages, of a climax ecosystem in an area that has not been occupied before, e.g., a rock face. Secondary succession: the reestablishment, through a series of stages, of a climax ecosystem in an area from which it was previously cleared.
|
|
| Sulfur cycle
|
| The chemical and physical reactions by which sulfur moves into or out of storage and through the environment.
|
|
| Sulfur dioxide
|
| A colorless, corrosive gas directly damaging to both plants and animals.
|
|
| Sulfuric acid (H2SO4)
|
| The major constituent of acid precipitation. Formed when sulfur dioxide emissions react with water vapor in the atmosphere. (See sulfur dioxide.)
|
|
| Sulfur oxides
|
| Sulfur dioxide and sulfur trioxide, common air pollutants arising from combustion of coal, oil, gasoline, and diesel fuel. Also produced by natural sources such as bacterial decay and hot springs. Sulfur dioxide reacts with oxygen to form sulfur trioxide, which may react with water to form sulfuric acid.
|
|
| Superfund
|
| A fund established by Congress to pay for containment, cleanup, or remediation of abandoned toxic waste sites. The fund is financed by fees paid by toxic waste generators and by cost-recovery from cleanup projects.
|
|
| Supply
|
| The quantity of that product being offered for sale at various prices, other things being equal.
|
|
| Supply and demand theory
|
| Economic theory explaining the price of goods and services. The supply of and demand for goods and services are primary price determinants. High demand diminishes supply, creating competition for existing goods and services, thus driving up prices.
|
|
| Surface impoundments
|
| Closed ponds formerly used to collect and hold liquid chemical wastes.
|
|
| Surface mining
|
| Some minerals are also mined from surface pits. See strip-mining.
|
|
| Surface runoff
|
| Water flowing in streams and over the ground during rainstorm or snowmelt.
|
|
| Surface tension
|
| A condition in which the water surface meets the air and acts like an elastic skin.
|
|
| Surface water
|
| Includes all bodies of water, lakes, rivers, ponds, and so on that are on Earth¡¦s surface in contrast to groundwater which lies below the surface.
|
|
| Surge flow irrigation
|
| Microprocessor control that allows the periodic release of irrigation water, thus cutting water use substantially.
|
|
| Survivorship
|
| The percentage of a population reaching a given age or the proportion of the maximum life span of the species reached by any individual.
|
|
| Suspended particulate matter (SPM)
|
| A category of major air pollutants consisting of solid and liquid particles suspended in the air.
|
|
| Suspension
|
| With reference to materials contained in or being carried by water, materials kept ¡§afloat¡¨ only by the water¡¦s agitation that settle as the water becomes quiet.
|
|
| Sustainability
|
| Refers to whether a process can be continued indefinitely without depleting the energy or material resources on which it depends. As one of the unifying themes of the text, the practical goal toward which our interactions with the natural world should be working.
|
|
| Sustainable agriculture
|
| An ecologically sound, economically viable, socially just, and humane agricultural system. Stewardship, soil conservation, and integrated pest management are essential for sustainability.
|
|
| Sustainable development
|
| A real increase in well-being and standard of life for the average person that can be maintained over the long-term without degrading the environment or compromising the ability of future generations to meet their own needs.
|
|
| Sustainable society
|
| One based on sustainable ethics. Lives within the limits imposed by nature and earth as a limited supply of resources, which must be cardfully managed to prevent irreparable damage. Obligations to future generations requires us to exercise restraint to ensure adequate resources and a clean and healthy environment.
|
|
| Sustainable forest management
|
| Management of forests as ecosystems where the primary objective of management is to maintain the biodiversity and function of the ecosystem.
|
|
| Sustainable society
|
| A society that functions in a way so as not to deplete the energy or material resources on which it depends. It interacts with the natural world in ways that sustain existing species and ecosystems.
|
|
| Sustained yield
|
| Utilization of a renewable resource at a rate that does not impair or damage its ability to be fully renewed on a long-term basis.
|
|
| Swamp
|
| Wetland with tree, such as the extensive swamp forests of the southern United States.
|
|
| Swidden agriculture
|
| See milpa agriculture.
|
|
| Symbiosis
|
| The intimate living together of members of two different species; includes mutualism, commensalisms, and, in some classifications, parasitism.
|
|
| Sympatric speciation
|
| Formation of new species without geographical isolation. Common in plants.
|
|
| Synergism
|
| The phenomenon in which two factors acting together have an exceedingly greater effect than would be indicated by the sum of their effects separately ¡V as, for example, the sometimes fatal mixture of modest doses of certain drugs in combination with modest doses of alcohol.
|
|
| Synergistic effects
|
| When an injury caused by exposure to two environmental factors together is greater than the sum of exposure to each factor individually.
|
|
| Synfuels, synthetic fuels
|
| Fuels similar or identical to those that come from crude oil and/or natural gas, produced from coal, oil shale, or tar sands.
|
|
| Synthetic fertilizer
|
| Same as inorganic fertilizer.
|
|
| Systemic
|
| A condition or process that affects the whole body; many metabolic poisons are systemic.
|
|
