水生生态学英文版

AquaticEcologyNotes\nChapterOverviewQuestionsWhatarethebasictypesofaquaticlifezonesandwhatfactorsinfluencethekindsoflifetheycontain?Whatarethemajortypesoffreshwaterlifezones,andhowdohumanactivitiesaffectthem?\nChapterOverviewQuestionsWhatdoweknowaboutaquaticbiodiversity,andwhatisitseconomicandecologicalimportance?Howarehumanactivitiesaffectingaquaticbiodiversity?Howcanwemanageandsustaintheworld’smarinefisheries?\nChapterOverviewQuestions(cont’d)Howcanweprotect,sustain,andrestorewetlands?Howcanweprotect,sustain,andrestorelakes,rivers,andfreshwaterfisheries?\nChapterOverviewQuestionsWhyiswatersoimportant,howmuchfreshwaterisavailabletous,andhowmuchofitareweusing?Whatcausesfreshwatershortages,andwhatcanbedoneaboutthisproblem?Whataretheadvantagesanddisadvantagesofwithdrawinggroundwater?Whataretheadvantagesanddisadvantagesofusingdamsandreservoirstosupplymorewater?\nChapterOverviewQuestions(cont’d)Whataretheadvantagesanddisadvantagesoftransferringlargeamountsofwaterfromoneplacetoanother?Canremovingsaltfromseawatersolveourwatersupplyproblems?Howcanwewastelesswater?Howcanweusetheearth’swatermoresustainably?Whatcausesflooding,andwhatcanwedoaboutit?\nWATER’SIMPORTANCE,AVAILABILITY,ANDRENEWALWaterkeepsusalive,moderatesclimate,sculptstheland,removesanddiluteswastesandpollutants,andmovescontinuallythroughthehydrologiccycle.Onlyabout0.02%oftheearth’swatersupplyisavailabletousasliquidfreshwater.\nWATER’SIMPORTANCE,AVAILABILITY,ANDRENEWALComparisonofpopulationsizesandsharesoftheworld’sfreshwateramongthecontinents.Figure14-2\nWATER’SIMPORTANCE,AVAILABILITY,ANDRENEWALSomeprecipitationinfiltratesthegroundandisstoredinsoilandrock(groundwater).Waterthatdoesnotsinkintothegroundorevaporateintotheairrunsoff(surfacerunoff)intobodiesofwater.Thelandfromwhichthesurfacewaterdrainsintoabodyofwateriscalleditswatershedordrainagebasin.\nFig.14-3,p.308UnconfinedAquiferRechargeAreaPrecipitationEvaporationandtranspirationEvaporationConfinedRechargeAreaRunoffFlowingartesianwellRechargeUnconfinedAquiferStreamWellrequiringapumpInfiltrationWatertableLakeInfiltrationUnconfinedaquiferConfinedaquiferConfiningimpermeablerocklayerLesspermeablematerialsuchasclay\nWATER’SIMPORTANCE,AVAILABILITY,ANDRENEWALWecurrentlyusemorethanhalfoftheworld’sreliablerunoffofsurfacewaterandcouldbeusing70-90%by2025.About70%ofthewaterwewithdrawfromrivers,lakes,andaquifersisnotreturnedtothesesources.Irrigationisthebiggestuserofwater(70%),followedbyindustries(20%)andcitiesandresidences(10%).\nSalinityThesaltiness.\nNiches\nWhatKindsofOrganismsLiveinAquaticLifeZones?Aquaticsystemscontainfloating,drifting,swimming,bottom-dwelling,anddecomposerorganisms.Plankton:importantgroupofweaklyswimming,free-floatingbiota.Phytoplankton(plant),Zooplankton(animal),Ultraplankton(photosyntheticbacteria)Necton:fish,turtles,whales.Benthos:bottomdwellers(barnacles,oysters).Decomposers:breakdownorganiccompounds(mostlybacteria).\nPhytoplanktonDescription–smalldriftingplantsNiche–theyareproducersthatsupportmostaquaticfoodchainsExample–cyanobacteria&manytypesofalgae\nZooplanktonDescription–herbivoresthatfeedonphytoplanktonorotherzooplanktonNiche–foodstockforlargerconsumersExample–krill;smallcrustaceans\nNektonDescription–larger,strong-swimmingconsumersNiche–topconsumersintheaquaticecosystemExample–fish,turtles,andwhales\nBenthosDescription–bottom-dwellingcreaturesNiche–primaryconsumers,decomposersExample–barnacles,oysters,andlobsters\nFreshwaterEcosystems\nFRESHWATERLIFEZONESFreshwaterlifezonesinclude:Standing(lentic)watersuchaslakes,ponds,andinlandwetlands.Flowing(lotic)systemssuchasstreamsandrivers.Figure6-14\nFlowingWaterEcosystemsBecauseofdifferentenvironmentalconditionsineachzone,ariverisasystemofdifferentecosystems.\nFig.12-11,p.267DelivernutrientstoseatohelpsustaincoastalfisheriesDepositsiltthatmaintainsdeltasPurifywaterRenewandrenourishwetlandsProvidehabitatsforwildlifeNaturalCapitalEcologicalServicesofRivers\nFreshwaterStreamsandRivers:FromtheMountainstotheOceansWaterflowingfrommountainstotheseacreatesdifferentaquaticconditionsandhabitats.Figure6-17\nHeadwaterStreamCharacteristicsAnarrowzoneofcold,clearwaterthatrushesoverwaterfallsandrapids.Largeamountsofoxygenarepresent.Fisharealsopresent.Ex.trout.\nDownstreamCharacteristicsSlower-movingwater,lessoxygen,warmertemperatures,andlotsofalgaeandcyanobacteria.\nEnergySourceGravity\nStandingWaterEcosystemsLakes,ponds,etc.\nLifeinLayersLifeinmostaquaticsystemsisfoundinsurface,middle,andbottomlayers.Temperature,accesstosunlightforphotosynthesis,dissolvedoxygencontent,nutrientavailabilitychangeswithdepth.Euphoticzone(upperlayerindeepwaterhabitats):sunlightcanpenetrate.\nLakes:Water-FilledDepressionsLakesarelargenaturalbodiesofstandingfreshwaterformedfromprecipitation,runoff,andgroundwaterseepageconsistingof:Littoralzone(nearshore,shallow,withrootedplants).Limneticzone(open,offshorearea,sunlit).Profundalzone(deep,openwater,toodarkforphotosynthesis).Benthiczone(bottomoflake,nourishedbydeadmatter).\nLittoralZoneAshallowareaneartheshore,tothedepthatwhichrootedplantsstopgrowing.Ex.frogs,snails,insects,fish,cattails,andwaterlilies.\nLimneticZoneOpen,sunlitwaterthatextendstothedepthpenetratedbysunlight.\nProfundalZoneDeep,openwaterwhereitistoodarkforphotosynthesis.\nThermalStratification\nLakes:Water-FilledDepressionsFigure6-15\nDefinitionThetemperaturedifferenceindeeplakeswheretherearewarmsummersandcoldwinters.\nLakes:Water-FilledDepressionsDuringsummerandwinterindeeptemperatezonelakesthebecomestratifiedintotemperaturelayersandwilloverturn.Thisequalizesthetemperatureatalldepths.Oxygenisbroughtfromthesurfacetothelakebottomandnutrientsfromthebottomarebroughttothetop.\nCausesDuringthesummer,lakesbecomestratifiedintodifferenttemperaturelayersthatresistmixingbecausesummersunlightwarmssurfacewaters,makingthemlessdense.\nThermoclineThemiddlelayerthatactsasabarriertothetransferofnutrientsanddissolvedoxygen.\nFallTurnoverAsthetemperaturesbegintodrop,thesurfacelayerbecomesmoredense,anditsinkstothebottom.Thismixingbringsnutrientsfromthebottomuptothesurfaceandsendsoxygentothebottom.\nSpringTurnoverAstopwaterwarmsandicemelts,itsinksthroughandbelowthecooler,lessdensewater,sendingoxygendownandnutrientsup.\nFreshwaterWetlands\nFreshwaterInlandWetlands:VitalSpongesInlandwetlandsactlikenaturalspongesthatabsorbandstoreexcesswaterfromstormsandprovideavarietyofwildlifehabitats.Figure6-18\nFreshwaterInlandWetlands:VitalSpongesFilteranddegradepollutants.Reducefloodinganderosionbyabsorbingslowlyreleasingoverflows.Helpreplenishstreamflowsduringdryperiods.Helprechargegroundaquifers.Provideeconomicresourcesandrecreation.\nMarshesAnareaoftemporarilyflooded,oftensiltylandbesideariverorlake.\nSwampsAlowlandregionpermanentlycoveredwithwater.\nHardwoodBottomlandForestAnareadownbyariverorstreamwherelotsofhardwoods,likeoaks,grow.\nPrairiePotholesThesearedepressionsthatholdwateroutontheprairie,especiallyupnorthinCanada.Itisaverygoodduckhabitat.\nPeatMossBogAwetareathatovertimefillsin(thelaststageofsuccessionispeatmoss).Itcanbeverydeep.InIreland,theyburnthisforwood.\nImportanceoffreshwaterwetlandsTheyfilter&purifywater.Habitatformanyanimalsandplants.\nHistoricalAspectsDevelopersandfarmerswantCongresstorevisethedefinitionofwetlands.Thiswouldmake60-75%ofallwetlandsunavailableforprotection.TheAudubonSocietyestimatesthatwetlandsprovidewaterqualityprotectionworth$1.6billionperyear,andtheysayifthatwetlandsaredestroyed,theU.S.wouldspend$7.7billionto$31billionperyearinadditionalflood-controlcosts.\nEstuaries\nDefinitionApartiallyenclosedareaofcoastalwaterwhereseawatermixeswithfreshwater.\nSaltMarshesThegroundhereissaturatedwithwaterandthereislittleoxygen,sodecaytakesplaceslowly.Ithasasurfaceinletandoutlet,andcontainsmanyinvertebrates.Itisalsothebreedinggroundformanyoceananimals.Ex.crabsandshellfish.\nMangroveForestsThesearealongwarm,tropicalcoastswherethereistoomuchsiltforcoralreefstogrow.Itisdominatedbysalt-toleranttreescalledmangroves(55differentspeciesexist).Italsohelpstoprotectthecoastlinefromerosionandprovidesabreedingnurseryforsome2000speciesoffish,invertebrates,andplants.\nImportanceofEstuariesJustoneacreofestuaryprovides$75,000worthoffreewastetreatment,andhasavalueofabout$83,000whenrecreationandfishforfoodareincluded.PrimeKansasfarmlandhasatopvalueof$1,200andanannualproductionvalueof$600.\nTheEvergladesSouthernFloridatotheKeys\nCaseStudy:RestoringtheFloridaEvergladesTheworld’slargestecologicalrestorationprojectinvolvestryingtoundosomeofthedamageinflictedontheEvergladesbyhumanactivities.90%ofpark’swadingbirdshavevanished.Othervertebratepopulationsdown75-95%.Largevolumesofwaterthatonceflowedthroughtheparkhavebeendivertedforcropsandcities.Runoffhascausednoxiousalgalblooms.\nProblemsAsMiamidevelops,itencroachesoneverglades.Plus,itpromptspeoplevs.wildlife.Itisfreshwaterandlocalareasaredrainingit.\nRestoringtheFloridaEvergladesTheprojecthasbeenattemptingtorestoretheEvergladesandFloridawatersupplies.Figure12-10\nRestorationBuildhugeaqueduct,orfindothersourcesoffreshwateranprotectitfederallyunderendangeredspeciesact,etc.\nTheWaterResource\nImportanceLeonardodaVincisaidthat“Wateristhedriverofnature.”Withoutwater,theothernutrientcycleswouldnotexistintheirpresentforms,andcurrentformsoflifeonearthcouldnotexist.\nHydrogenBonds\nAttractionBetweenMoleculesThestrongforcesofattractionbetweenmoleculesofwater.\nHeatCapacityWaterchangestempveryslowlybecauseitcanstoreheat.Thisprotectslivingorganismsfromtheshockofabrupttemperaturechanges.\nHeatofVaporizationThetemperatureatwhichwaterturnstovapor.\nUniversalSolventWatercandissolveawidevarietyofcompounds.Thismeansitcaneasilybecomepollutedbywater-solublewastes.\nExpansionWhenFrozenIcehasalowerdensitythanliquidwater.Thus,icefloatsonwater.\nHydrologicCycle\nSurfaceWaterExamples–streams,rivers,andlakesSource–precipitationWatershed–Ex.smallstreamslargerstreamsriverssea\nGroundwaterAquifers–porousrockw/waterflowingthroughWaterTable–thelevelofearth’slandcrusttowhichtheaquiferisfilledRenewability–thecirculationrateofgroundwaterisslow(300to4,600years).\nWaterUsageIrrigation–wateringcropsIndustry–coolant(powerplant)DomesticandMunicipal–drinking,sewage,bathwater,dishwater&laundry\nProblems\nTooMuchWaterProblemsincludeflooding,pollutionofwatersupply,andsewageseepingintotheground.\nTOOMUCHWATERHeavyrainfall,rapidsnowmelt,removalofvegetation,anddestructionofwetlandscauseflooding.Floodplains,whichusuallyincludehighlyproductivewetlands,helpprovidenaturalfloodanderosioncontrol,maintainhighwaterquality,andrechargegroundwater.Tominimizefloods,rivershavebeennarrowedwithleveesandwalls,anddammedtostorewater.\nTOOMUCHWATERComparisonofSt.Louis,Missouriundernormalconditions(1988)andaftersevereflooding(1993).Figure14-22\nTOOMUCHWATERHumanactivitieshavecontributedtoflooddeathsanddamages.Figure14-23\nFig.14-23a,p.330OxygenreleasedbyvegetationDiverseecologicalhabitatEvapotranspirationTreesreducesoilerosionfromheavyrainandwindAgriculturallandSteadyriverflowLeaflitterimprovessoilfertilityTreerootsstabilizesoilandaidwaterflowVegetationreleaseswaterslowlyandreducesfloodingForestedHillside\nFig.14-23b,p.330TreeplantationRoadsdestabilizehillsidesEvapotranspirationdecreasesRanchingacceleratessoilerosionbywaterandwindWindsremovefragiletopsoilAgriculturallandisfloodedandsiltedupGulliesandlandslidesHeavyrainleachesnutrientsfromsoilanderodestopsoilSiltfromerosionblocksriversandreservoirsandcausesfloodingdownstreamRapidrunoffcausesfloodingAfterDeforestation\nTooLittleWater\nExamplesExamplesincludedroughtandexpandingdeserts.\nOverdrawingSurfaceWaterLakelevelsdrop,recreationusedrops,fisheriesdrop,andsalinizationoccurs.Ex.SovietUnion(AralSea);theinlandseadrainedtheriverthatfedintoit.Nowit’sahugedisaster(readpg.322intext).19641997\nCaseStudy:TheAralSeaDisasterDivertingwaterfromtheAralSeaanditstwofeederriversmostlyforirrigationhascreatedamajorecological,economic,andhealthdisaster.About85%ofthewetlandshavebeeneliminatedandroughly50%ofthelocalbirdandmammalspecieshavedisappeared.Since1961,thesea’ssalinityhastripledandthewaterhasdroppedby22metersmostlikelycausing20ofthe24nativefishspeciestogoextinct.\nAquiferDepletionThisharmsendangeredspecies,andsaltwatercanseepin.\nSalinizationofIrrigatedSoilWaterispouredontosoilandevaporates.Overtime,asthisisrepeated,nothingwillgrowthereanymore.\nU.S.WaterProblems\nSurfaceWaterProblemsThepollutedMississippiRiver(non-sourcepointpollution)hastoomuchphosphorus.IntheEerieCanal,whichconnectstheoceantotheGreatLakes,lampreyscameinanddepletedthefish.ThezebramolluskisalsoaproblemintheGreatLakes.\nEffectsofPlantNutrientsonLakes:TooMuchofaGoodThingPlantnutrientsfromalake’senvironmentaffectthetypesandnumbersoforganismsitcansupport.Figure6-16\nEffectsofPlantNutrientsonLakes:TooMuchofaGoodThingPlantnutrientsfromalake’senvironmentaffectthetypesandnumbersoforganismsitcansupport.Oligotrophic(poorlynourished)lake:Usuallynewlyformedlakewithsmallsupplyofplantnutrientinput.Eutrophic(wellnourished)lake:Overtime,sediment,organicmaterial,andinorganicnutrientswashintolakescausingexcessiveplantgrowth.\nEffectsofPlantNutrientsonLakes:TooMuchofaGoodThingCulturaleutrophication:Humaninputsofnutrientsfromtheatmosphereandurbanandagriculturalareascanacceleratetheeutrophicationprocess.\nMonoLake(liketheDeadSea)Thishasahugesaltconcentrationduetoman’sdraining.\nColoradoRiverBasinThesearedams&reservoirsthatfeedfromtheColoradoRiverallthewaytoSanDiego,LA,PalmSprings,Phoenix&Mexico.Sofarhasworkedbecausetheyhaven’twithdrawntheirfullallocations.Seepg306.\nTheColoradoRiverBasinTheareadrainedbythisbasinisequaltomorethanone-twelfthofthelandareaofthelower48states.Figure14-14\nFig.14-14,p.318DamAqueductorcanalUpperBasinLOWERBASIN0100mi.0150kmLowerBasinUPPERBASINIDAHOWYOMINGSaltLakeCityGrandJunctionDenverUTAHNEVADACOLORADOLakePowellLasVegasGrandCanyonGlenCanyonDamBoulderCityNEWMEXICOARIZONALosAngelesAlbuquerquePhoenixSanDiegoMexicaliYumaTucsonAll-AmericanCanalGulfofCaliforniaMEXICOCALIFORNIAPalmSpringsColoradoRiver\nCaseStudy:TheColoradoBasin–anOvertappedResourceTheColoradoRiverhassomanydamsandwithdrawalsthatitoftendoesnotreachtheocean.14majordamsandreservoirs,andcanals.WaterismostlyusedindesertareaoftheU.S.Provideselectricityfromhydroelectricplantsfor30millionpeople(1/10thoftheU.S.population).\nCaseStudy:TheColoradoBasin–anOvertappedResourceLakePowell,isthesecondlargestreservoirintheU.S.IthostsoneofthehydroelectricplantslocatedontheColoradoRiver.Figure14-15\nGroundwaterProblemsTheseincludepollution,salt,anddrainingtoomuch.\nOtherEffectsofGroundwaterOverpumpingSinkholesformwhentheroofofanundergroundcaverncollapsesafterbeingdrainedofgroundwater.Figure14-10\nGroundwaterDepletion:AGrowingProblemTheOgallala,theworld’slargestaquifer,ismostoftheredareainthecenter(Midwest).AreasofgreatestaquiferdepletionfromgroundwateroverdraftinthecontinentalU.S.Figure14-8\nOgallalaAquiferThisistheworld’slargestknownaquifer,andfuelsagriculturalregionsintheU.S.ItextendsfromSouthDakotatoTexas.It’sessentiallyanon-renewableaquiferfromthelasticeagewithanextremelyslowrechargerate.Insomecases,waterispumpedout8to10timesfasterthanitisrenewed.Northernstateswillstillhaveamplesupplies,butforthesouthit’sgettingthinner.Itisestimatedthat¼oftheaquiferwillbedepletedby2020.\nGlobalWaterProblems\nImpactsofHumanActivitiesonFreshwaterSystemsDams,cities,farmlands,andfilled-inwetlandsalteranddegradefreshwaterhabitats.Dams,diversionsandcanalshavefragmentedabout40%oftheworld’s237largerivers.Floodcontrolleveesanddikesalteranddestroyaquatichabitats.Citiesandfarmlandsaddpollutantsandexcessplantnutrientstostreamsandrivers.Manyinlandwetlandshavebeendrainedorfilledforagricultureor(sub)urbandevelopment.\nCoreCaseStudy:ABiologicalRollerCoasterRideinLakeVictoriaLakeVictoriahaslosttheirendemicfishspeciestolargeintroducedpredatoryfish.Figure12-1\nCoreCaseStudy:ABiologicalRollerCoasterRideinLakeVictoriaReasonsforLakeVictoria’slossofbiodiversity:IntroductionofNileperch.Lakeexperiencedalgalbloomsfromnutrientrunoff.Invasionofwaterhyacinthhasblockedsunlightanddeprivedoxygen.Nileperchisindeclinebecauseithaseatenitsownfoodsupply.\nStableRunoffAswaterrunsofffromrain,it’ssupposedtogetintorivers,andfinallyofftothesea.Butwhenwedamrivers,lessgoestotheocean,meaningthebrackishwater(wheretheriverhitstheocean)becomesmoresalty.Thisisthebreedinggroundformanyfishandinvertebrates.Thisharmstheecologyofthearea.\nDrinkingWaterProblems\nColiformBacteriaTheW.H.O.recommendstherebezerocoloniesofbacteriaper100mlofdrinkingwaterand200coloniesper100mlofswimmingwater.Theaveragehumanexcretes2billionorganismsperday(seehoweasilyuntreatedsewagecancontaminatewater?).\nOxygenDemandingWastesTheseareorganicwastesthatcanbedecomposedbyaerobicbacteria(causeslackofoxygen).Fishdieasaresultofalackofoxygen.\nWater-SolubleInorganicChemicalsTheseincludeacids,salts,mercury,andlead.Theymakewaterunfittodrink.\nOrganicMaterialTheseincludeoil,gas,plastics,pesticides,anddetergents.\nPopulationGrowthProblemsincludeover-drawingfreshwater,pollution,andover-buildingsothatwatercan’tseepintotheground.\nSharingWaterResourcesTherearewaterwarsoutwest.CaliforniaboughtthewaterfromtheColoradoRiver,butArizonawantsit.Whoownsit?ThesamethingishappeninginTexas.Morewaterrightsaresoldthantheactualamountofwater.Howdoyousharewater?Thisisaproblemallovertheworld.\nWaterManagement\nDamsandReservoirsDescription:Adammedstreamthatcancapture&storewaterfromrain&meltedsnow.Benefits:Hydroelectricpower;provideswatertotowns;recreation;controlsfloodsdownstreamProblems:Reducesdownstreamflow;preventswaterfromreachingthesea(ColoradoRiver)devastatesfishlife;reducesbiodiversity.\nUSINGDAMSANDRESERVOIRSTOSUPPLYMOREWATERLargedamsandreservoirscanproducecheapelectricity,reducedownstreamflooding,andprovideyear-roundwaterforirrigatingcropland,buttheyalsodisplacepeopleanddisruptaquaticsystems.\nFig.14-13a,p.317Provideswaterforyear-roundirrigationofcroplandFloodedlanddestroysforestsorcroplandanddisplacespeopleLargelossesofwaterthroughevaporationProvideswaterfordrinkingDownstreamcroplandandestuariesaredeprivedofnutrient-richsiltReservoirisusefulforrecreationandfishingRiskoffailureanddevastatingdownstreamfloodingCanproducecheapelectricity(hydropower)DownstreamfloodingisreducedMigrationandspawningofsomefisharedisrupted\nFig.14-13b,p.317PowerlinesReservoirDamPowerhouseIntakeTurbine\nCaseStudy:China’sThreeGorgesDamThereisadebateoverwhethertheadvantagesoftheworld’slargestdamandreservoirwilloutweighitsdisadvantages.Thedamwillbe2kilometerslong.Theelectricoutputwillbethatof18largecoal-burningornuclearpowerplants.Itwillfacilitateshiptravelreducingtransportationcosts.Damwilldisplace1.2millionpeople.Damisbuiltoverseismaticfaultandalreadyhassmallcracks.\nDamRemovalSomedamsarebeingremovedforecologicalreasonsandbecausetheyhaveoutlivedtheirusefulness.In1998theU.S.ArmyCorpsofEngineersannouncedthatitwouldnolongerbuildlargedamsanddiversionprojectsintheU.S.TheFederalEnergyRegulatoryCommissionhasapprovedtheremovalofnearly500dams.Removingdamscanreestablishecosystems,butcanalsore-releasetoxicantsintotheenvironment.\nWaterDiversionDescription:DammingarivertocontrolwherethewaterflowsBenefits:Keepswaterwherewewantit-cities!Problems:Drainswetlands,destroysland\nDesalinizationDescription:RemovingsaltfromsaltwaterBenefits:FreshwaterProblems:Useslotsofenergy;costs3-5X’smoremoney;whatdowedowiththesalt?\nDESALTINGSEAWATER,SEEDINGCLOUDS,ANDTOWINGICEBERGSANDGIANTBAGGIESRemovingsaltfromseawaterbycurrentmethodsisexpensiveandproduceslargeamountsofsaltywastewaterthatmustbedisposedofsafely.Distillation:heatingsaltwateruntilitevaporates,leavesbehindwaterinsolidform.Reverseosmosis:useshighpressuretoforcesaltwaterthroughamembranefilter.\nDESALTINGSEAWATER,SEEDINGCLOUDS,ANDTOWINGICEBERGSANDGIANTBAGGIESSeedingcloudswithtinyparticlesofchemicalstoincreaserainfalltowingicebergsorhugebagsfilledwithfreshwatertodrycoastalareashaveallbeenproposedbutareunlikelytoprovidesignificantamountsoffreshwater.\nHarvestingIcebergsDescription:Towingmassiveicebergstoaridcoastalareas(S.California;SaudiArabia)Benefits:freshwaterProblems:Technologynotavailable;coststoohigh;raisetemperaturesaroundtheearth.\nINCREASINGWATERSUPPLIESBYWASTINGLESSWATERSixtypercentoftheworld’sirrigationwateriscurrentlywasted,butimprovedirrigationtechniquescouldcutthiswasteto5-20%.Center-pivot,lowpressuresprinklerssprayswaterdirectlyontocrop.Itallows80%ofwatertoreachcrop.HasreduceddepletionofOgallalaaquiferinTexasHighPlainsby30%.\nFig.14-18,p.325CenterpivotDripirrigationGravityflow(efficiency60%and80%withsurgevalves)Above-orbelow-groundpipesortubesdeliverwatertoindividualplantroots.Waterusuallycomesfromanaqueductsystemoranearbyriver.(efficiency90–95%)(efficiency80%–95%)Waterusuallypumpedfromundergroundandsprayedfrommobileboomwithsprinklers.\nConservationDescription:SavingthewaterwehaveMethods:recycling;conservingathome;xeriscaping;fixleaksBenefits:Savesmoney;SavesWildlifeProblems:bothersometopeople;lackofcaring;laziness\nFishingProblems&TechniquesThemajordeclineintheworldwidecatchoffishsince1990isbecauseofover-fishing.By-catch-fishoranimalsthatwerenotmeanttobecaught.\nOverfishingandExtinction:GoneFishing,FishGoneAbout75%oftheworld’scommerciallyvaluablemarinefishspeciesareoverfishedorfishedneartheirsustainablelimits.Bigfisharebecomingscarce.Smallerfisharenext.Wethrowaway30%ofthefishwecatch.Weneedlesslykillseamammalsandbirds.\nFig.12-A,p.255FishfarmingincageTrawlerfishingSpotterairplaneSonarTrawlflapTrawllinesPurse-seinefishingTrawlbagFishschoolDrift-netfishingLonglinefishingLineswithhooksFishcaughtbygillsDeepseaaquaculturecageFloatBuoy\nPurseSeines\nPurseSeinesAlargepurse-likenetisputintotheoceanandisthenclosedlikeadrawstringpursetotrapthefish.TunaisafishtypicallycaughtinpurseseinesDolphinsareaby-catchofpurseseines\nLong-linefishingLinesareputoutthatcanbeupto80mileslongw/thousandsofbaitedhooksonthem.Theseareleftoutfree-floatingfordaysandthentheboatcomesbackandpicksthemup.Pilotwhales,dolphins,seaturtles,andbirdsareby-catchofthistechnique.\nDrift-netfishingEachnethangsasmuchas50feetbelowthesurfaceandupto34mileslong.Anythingthatcomesintocontactw/thesenearlyinvisiblenetsareentangled.ThisleadstooverfishingManyunwantedfishandmarinemammals,turtlesandseabirdsarecaught.\nHUMANIMPACTSONAQUATICBIODIVERSITYAreaofoceanbeforeandafteratrawlernet,actinglikeagiantplow,scrapedit.Figure12-2\nPopulationGrowthandPollutionEachyearplasticitemsdumpedfromshipsandleftaslitteronbeachesthreatenmarinelife.Figure12-3