Environmental Problems, Their Causes, and Sustainability 1

soil permeability Rate at which water andair move from upper to lower soil layers.Compare porosity.soil porosity See porosity.soil profile Cross-sectional view of thehorizons in a soil. See soil horizon.soil structure How the particles that makeup a soil are organized and clumpedtogether. See also soil permeability, soiltexture.soil texture Relative amounts of the differenttypes and sizes of mineral particles in asample of soil.solar capital Solar energy from the sunreaching the earth. Compare naturalresources.solar cell See photovoltaic cell.solar collector Device for collecting radiantenergy from the sun and converting itinto heat. See active solar heating system,passive solar heating system.solar energy Direct radiant energy fromthe sun and a number of indirect forms ofenergy produced by the direct input. Principalindirect forms of solar energy includewind, falling and flowing water(hydropower), and biomass (solar energyconverted into chemical energy stored inthe chemical bonds of organic compoundsin trees and other plants).solid waste Any unwanted or discardedmaterial that is not a liquid or a gas. Seemunicipal solid waste.sound science Scientific data, models,theories, and laws that are widely acceptedby scientists considered experts in thearea of study. These results of science arevery reliable. Compare frontier science, junkscience.spaceship-earth worldview View of theearth as a spaceship: a machine that we canunderstand, control, and change at will byusing advanced technology. See planetarymanagement worldview. Compare environmentalwisdom worldview, stewardship worldview.specialist species Species with a narrowecological niche. They may be able to live inonly one type of habitat, tolerate only a narrowrange of climatic and other environmentalconditions, or use only one type or afew types of food. Compare generalist species.speciation Formation of two species fromone species because of divergent naturalselection in response to changes in environmentalconditions; usually takes thousandsof years. Compare extinction.species Group of organisms that resembleone another in appearance, behavior, chemicalmakeup and processes, and geneticstructure. Organisms that reproduce sexuallyare classified as members of the samespecies only if they can actually or potentiallyinterbreed with one another and producefertile offspring.species diversity Number of differentspecies (species richness) and their relativeabundances (species evenness) in a givenarea or community. See biodiversity. Compareecological diversity, genetic diversity.species equilibrium model See theory ofisland biography.species evenness Number of individualswithin a species in a community. See speciesdiversity, species richness.species richness Number of differentspecies in a community.spoils Unwanted rock and other wastematerials produced when a material isremoved from the earth’s surface or subsurfaceby mining, dredging, quarrying, andexcavation.S-shaped curve Leveling off of an exponential,J-shaped curve when a rapidlygrowing population exceeds the carryingcapacity of its environment and ceases togrow.stability Ability of a living system towithstand or recover from externallyimposed changes or stresses. See constancy,inertia, resilience.statutory law Law developed and passedby legislative bodies such as federal andstate governments. Compare common law.stewardship worldview (1) we are theplanet’s most important species but we havean ethical responsibility to care for the restof nature; (2) we will probably not run out ofresources but they should not be wasted;(3) we should encourage environmentallybeneficial forms of economic growth anddiscourage environmentally harmful formsof economic growth; and (4) our successdepends on how well we can understand,control, and manage and care for the earth’slife-support systems for our benefit and forthe rest of nature. Compare environmentalwisdom worldview, planetary managementworldview, spaceship earth worldview.stratosphere Second layer of the atmosphere,extending about 17–48 kilometers(11–30 miles) above the earth’s surface.It contains small amounts of gaseousozone (O 3 ), which filters out about 95%of the incoming harmful ultraviolet (UV)radiation emitted by the sun. Comparetroposphere.stream Flowing body of surface water.Examples are creeks and rivers.strip cropping Planting regular crops andclose-growing plants, such as hay or nitrogen-fixinglegumes, in alternating rows orbands to help reduce depletion of soilnutrients.strip cutting A variation of clear-cuttingin which a strip of trees is clear-cut alongthe contour of the land, with the corridornarrow enough to allow natural regenerationwithin a few years. After regeneration,another strip is cut above the first, and soon. Compare clear-cutting, seed-tree cutting,selective cutting, shelterwood cutting.strip mining Form of surface mining inwhich bulldozers, power shovels, or strippingwheels remove large chunks of theearth’s surface in strips. See area strip mining,contour strip mining, surface mining.Compare subsurface mining.subatomic particles Extremely small particles—electrons,protons, and neutrons—that make up the internal structure ofatoms.subduction zone Area in which oceaniclithosphere is carried downward (subducted)under the island arc or continent ata convergent plate boundary. A trench ordinarilyforms at the boundary between thetwo converging plates. See convergent plateboundary.subsidence Slow or rapid sinking of partof the earth’s crust that is not slope-related.subsistence farming Supplementing solarenergy with energy from human labor anddraft animals to produce enough food tofeed oneself and family members; in goodyears enough food may be left over to sellor put aside for hard times. Compare industrializedagriculture.subsurface mining Extraction of a metalore or fuel resource such as coal from a deepunderground deposit. Compare surfacemining.succession See ecological succession, primarysuccession, secondary succession.succulent plants Plants, such as desertcacti, that survive in dry climates by havingno leaves, thus reducing the loss of scarcewater. They store water and use sunlight toproduce the food they need in the thick,fleshy tissue of their green stems andbranches. Compare deciduous plants, evergreenplants.sulfur cycle Cyclic movement of sulfur indifferent chemical forms from the environmentto organisms and then back to theenvironment.superinsulated house House that isheavily insulated and extremely airtight.Typically, active or passive solar collectorsare used to heat water, and an air-to-airheat exchanger is used to prevent buildupof excessive moisture and indoor airpollutants.surface fire Forest fire that burns onlyundergrowth and leaf litter on the forestfloor. Compare crown fire, ground fire. Seecontrolled burning.surface mining Removing soil, subsoil,and other strata and then extracting amineral deposit found fairly close tothe earth’s surface. See area strip mining,contour strip mining, dredging, mountaintopremoval, open-pit mining. Compare subsurfacemining.surface runoff Water flowing off the landinto bodies of surface water. See reliablerunoff.surface water Precipitation that doesnot infiltrate the ground or return tothe atmosphere by evaporation or transpiration.See runoff. Comparegroundwater.survivorship curve Graph showing thenumber of survivors in different age groupsfor a particular species.sustainability Ability of a system to survivefor some specified (finite) time.GLOSSARYG17