Environmental Problems, Their Causes, and Sustainability 1

sustainable agriculture Method of growingcrops and raising livestock based onorganic fertilizers, soil conservation, waterconservation, biological pest control, andminimal use of nonrenewable fossil-fuelenergy.sustainable development See environmentallysustainable economic development.sustainable living Taking no more potentiallyrenewable resources from the naturalworld than can be replenished naturallyand not overloading the capacity of theenvironment to cleanse and renew itself bynatural processes.sustainable society A society that managesits economy and population sizewithout doing irreparable environmentalharm by overloading the planet’s ability toabsorb environmental insults, replenish itsresources, and sustain human and otherforms of life over a specified period, usuallyhundreds to thousands of years. During thisperiod, it satisfies the needs of its peoplewithout depleting natural resources andthereby jeopardizing the prospects of currentand future generations of humans andother species.sustainable yield (sustained yield) Highestrate at which a potentially renewableresource can be used without reducing itsavailable supply throughout the world or ina particular area. See also environmentaldegradation.symbiosis Any intimate relationship orassociation between members of two ormore species. See symbiotic relationship.symbiotic relationship Species interactionin which two kinds of organisms livetogether in an intimate association. Membersof the participating species may beharmed by, benefit from, or be unaffectedby the interaction. See commensalism, interspecificcompetition, mutualism, parasitism,predation.synergistic interaction Interaction of twoor more factors or processes so that thecombined effect is greater than the sum oftheir separate effects.synergy See synergistic interaction.synfuels Synthetic gaseous and liquidfuels produced from solid coal or sourcesother than natural gas or crude oil.synthetic natural gas (SNG) Gaseous fuelcontaining mostly methane produced fromsolid coal.system A set of components that functionand interact in some regular and theoreticallypredictable manner.tailings Rock and other waste materialsremoved as impurities when waste mineralmaterial is separated from the metal in anore.tar sand See oil sand.tectonic plates Various-sized areas of theearth’s lithosphere that move slowlyaround with the mantle’s flowing asthenosphere.Most earthquakes and volcanoesoccur around the boundaries of these plates.See lithosphere, plate tectonics.temperature Measure of the average speedof motion of the atoms, ions, or molecules ina substance or combination of substances ata given moment. Compare heat.temperature inversion Layer of dense,cool air trapped under a layer of less dense,warm air. This prevents upward-flowing aircurrents from developing. In a prolongedinversion, air pollution in the trapped layermay build up to harmful levels. See radiationtemperature inversion, subsidence temperatureinversion.teratogen Chemical, ionizing agent, orvirus that causes birth defects. Compare carcinogen,mutagen.terracing Planting crops on a long, steepslope that has been converted into a seriesof broad, nearly level terraces with shortvertical drops from one to another that runalong the contour of the land to retain waterand reduce soil erosion.terrestrial Pertaining to land. Compareaquatic.territoriality Process in which organismspatrol or mark an area around their home,nesting, or major feeding site and defend itagainst members of their own species.tertiary (higher-level) consumers Animalsthat feed on animal-eating animals.They feed at high trophic levels in foodchains and webs. Examples are hawks,lions, bass, and sharks. Compare detritivore,primary consumer, secondary consumer.tertiary sewage treatment See advancedsewage treatment.theory of evolution Widely acceptedscientific idea that all life forms developedfrom earlier life forms. Although thistheory conflicts with the creation stories ofmany religions, it is the way biologistsexplain how life has changed over the past3.6–3.8 billion years and why it is so diversetoday.theory of island biogeography Thenumber of species found on an island isdetermined by a balance between twofactors: the immigration rate (of speciesnew to the island) from other inhabitedareas and the extinction rate (of speciesestablished on the island). The model predictsthat at some point the rates of immigrationand extinction will reach an equilibriumpoint that determines the island’saverage number of different species (speciesdiversity).thermal inversion See temperatureinversion.thermocline Zone of gradual temperaturedecrease between warm surface water andcolder deep water in a lake, reservoir, orocean.threatened species Awild species that isstill abundant in its natural range but islikely to become endangered because of adecline in numbers. Compare endangeredspecies.threshold effect The harmful or fataleffect of a small change in environmentalconditions that exceeds the limit of toleranceof an organism or population of aspecies. See law of tolerance.throughput Rate of flow of matter, energy,or information through a system. Compareinput, output.throwaway society See high-throughputeconomy.time delay Time lag between the input ofa stimulus into a system and the response tothe stimulus.tolerance limits Minimum and maximumlimits for physical conditions (such as temperature)and concentrations of chemicalsubstances beyond which no members of aparticular species can survive. See law of tolerance.total fertility rate (TFR) Estimate of theaverage number of children who will beborn alive to a woman during her lifetime ifshe passes through all her childbearingyears (ages 15–44) conforming to age-specificfertility rates of a given year. In simplerterms, it is an estimate of the average numberof children a woman will have duringher childbearing years.toxic chemical See poison.See carcinogen,hazardous chemical, mutagen, teratogen.toxicity Measure of how harmful a substanceis.toxicology Study of the adverse effects ofchemicals on health.toxic waste Form of hazardous waste thatcauses death or serious injury (such asburns, respiratory diseases, cancers, orgenetic mutations). See hazardous waste.toxin See poison.traditional intensive agriculture Producingenough food for a farm family’s survivaland perhaps a surplus that can besold. This type of agriculture uses higherinputs of labor, fertilizer, and water thantraditional subsistence agriculture. See traditionalsubsistence agriculture. Compareindustrialized agriculture.traditional subsistence agriculture Productionof enough crops or livestock for afarm family’s survival and, in good years, asurplus to sell or put aside for hard times.Compare industrialized agriculture, traditionalintensive agriculture.tragedy of the commons Depletion ordegradation of a potentially renewableresource to which people have free andunmanaged access. An example is thedepletion of commercially desirable fishspecies in the open ocean beyond areas controlledby coastal countries. See commonpropertyresource.transform fault Area where the earth’slithospheric plates move in opposite butparallel directions along a fracture (fault) inthe lithosphere. Compare convergent plateboundary, divergent plate boundary.transgenic organisms See genetically modifiedorganisms (GMOs).G18GLOSSARY