Bài giảng Biology - Chapter 55: Conservation Biology and Restoration Ecology

Chapter 55Conservation Biology and Restoration EcologyOverview: The Biodiversity CrisisConservation biology integrates the following fields to conserve biological diversity at all levelsEcologyEvolutionary biologyPhysiologyMolecular biologyGeneticsBehavioral ecologyRestoration ecology applies ecological principlesIn an effort to return degraded ecosystems to conditions as similar as possible to their natural stateTropical forestsContain some of the greatest concentrations of speciesAre being destroyed at an alarming rateFigure 55.1Throughout the biosphere, human activitiesAre altering ecosystem processes on which we and other species dependConcept 55.1: Human activities threaten Earth’s biodiversityRates of species extinctionAre difficult to determine under natural conditionsThe current rate of species extinction is highAnd is largely a result of ecosystem degradation by humansHumans are threatening Earth’s biodiversityThe Three Levels of BiodiversityBiodiversity has three main componentsGenetic diversitySpecies diversityEcosystem diversityGenetic diversity in a vole populationSpecies diversity in a coastal redwood ecosystemCommunity and ecosystem diversityacross the landscape of an entire regionFigure 55.2Genetic DiversityGenetic diversity comprisesThe genetic variation within a populationThe genetic variation between populationsSpecies DiversitySpecies diversityIs the variety of species in an ecosystem or throughout the biosphereAn endangered speciesIs one that is in danger of becoming extinct throughout its rangeThreatened speciesAre those that are considered likely to become endangered in the foreseeable futureConservation biologists are concerned about species lossBecause of a number of alarming statistics regarding extinction and biodiversityHarvard biologist E. O. Wilson has identified the Hundred Heartbeat ClubSpecies that number fewer than 100 individuals and are only that many heartbeats from extinction(a) Philippine eagle(b) Chinese river  dolphin(c) Javan  rhinocerosFigure 55.3a–cEcosystem DiversityEcosystem diversityIdentifies the variety of ecosystems in the biosphereIs being affected by human activityBiodiversity and Human WelfareHuman biophiliaAllows us to recognize the value of biodiversity for its own sakeSpecies diversityBrings humans many practical benefitsBenefits of Species and Genetic DiversityMany pharmaceuticalsContain substances originally derived from plantsFigure 55.4The loss of speciesAlso means the loss of genes and genetic diversityThe enormous genetic diversity of organisms on EarthHas the potential for great human benefitEcosystem ServicesEcosystem services encompass all the processesThrough which natural ecosystems and the species they contain help sustain human life on EarthEcosystem services includePurification of air and waterDetoxification and decomposition of wastesCycling of nutrientsModeration of weather extremesAnd many othersFour Major Threats to BiodiversityMost species loss can be traced to four major threatsHabitat destructionIntroduced speciesOverexploitationDisruption of “interaction networks”Habitat DestructionHuman alteration of habitatIs the single greatest threat to biodiversity throughout the biosphereMassive destruction of habitatHas been brought about by many types of human activityMany natural landscapes have been broken upFragmenting habitat into small patchesFigure 55.5In almost all casesHabitat fragmentation and destruction leads to loss of biodiversityIntroduced SpeciesIntroduced speciesAre those that humans move from the species’ native locations to new geographic regionsIntroduced species that gain a foothold in a new habitatUsually disrupt their adopted community(a) Brown tree  snake, intro- duced to Guam  in cargo(b) Introduced kudzu thriving in South CarolinaFigure 55.6a, bOverexploitationOverexploitation refers generally to the human harvesting of wild plants or animalsAt rates exceeding the ability of populations of those species to reboundThe fishing industryHas caused significant reduction in populations of certain game fishFigure 55.7Disruption of Interaction NetworksThe extermination of keystone species by humansCan lead to major changes in the structure of communitiesFigure 55.8Concept 55.2: Population conservation focuses on population size, genetic diversity, and critical habitatBiologists focusing on conservation at the population and species levelsFollow two main approachesSmall-Population ApproachConservation biologists who adopt the small-population approachStudy the processes that can cause very small populations finally to become extinctThe Extinction VortexA small population is prone to positive-feedback loopsThat draw the population down an extinction vortexSmallpopulationInbreedingGeneticdriftLower reproductionHigher mortalityLoss ofgeneticvariabilityReduction inindividualfitness andpopulationadaptabilitySmallerpopulationFigure 55.9The key factor driving the extinction vortexIs the loss of the genetic variation necessary to enable evolutionary responses to environmental changeCase Study: The Greater Prairie Chicken and the Extinction VortexPopulations of the greater prairie chickenWere fragmented by agriculture and later found to exhibit decreased fertilityAs a test of the extinction vortex hypothesisScientists imported genetic variation by transplanting birds from larger populationsThe declining population reboundedConfirming that it had been on its way down an extinction vortexEXPRIMENT Researchers observed that the population collapse of the greater prairie chicken was mirrored in a reduction in fertility, as measured by the hatching rate of eggs. Comparison of DNA samples from the Jasper County, Illinois, population with DNA from feathers in museum specimens showed that genetic variation had declined in the study population. In 1992, researchers began experimental translocations of prairie chickens from Minnesota, Kansas, and Nebraska in an attempt to increase genetic variation. RESULTS After translocation (blue arrow), the viability of eggs rapidly improved, and the population rebounded.CONCLUSION The researchers concluded that lack of genetic  variation had started the Jasper County population of prairie chickens down the extinction vortex.Number of male birds(a) Population dynamics(b) Hatching rate2001501005001970197519801985199019952000YearEggs hatched (%)100908070605040301970-741975-791980-841985-8919901993-97YearsFigure 55.10Minimum Viable Population SizeThe minimum viable population (MVP)Is the minimum population size at which a species is able to sustain its numbers and surviveA population viability analysis (PVA)Predicts a population’s chances for survival over a particular timeFactors in the MVP of a populationEffective Population SizeA meaningful estimate of MVPRequires a researcher to determine the effective population size, which is based on the breeding size of a populationCase Study: Analysis of Grizzly Bear PopulationsOne of the first population viability analysesWas conducted as part of a long-term study of grizzly bears in Yellowstone National ParkFigure 55.11This study has shown that the grizzly bear populationHas grown substantially in the past 20 yearsNumber of individuals1501005001973198219912000Females with cubsCubsYearFigure 55.12Declining-Population ApproachThe declining-population approachFocuses on threatened and endangered populations that show a downward trend, regardless of population sizeEmphasizes the environmental factors that caused a population to decline in the first placeSteps for Analysis and InterventionThe declining-population approachRequires that population declines be evaluated on a case-by-case basisInvolves a step-by-step proactive conservation strategyCase Study: Decline of the Red-Cockaded WoodpeckerRed-cockaded woodpeckersRequire specific habitat factors for survivalHad been forced into decline by habitat destruction(a) A red-cockaded woodpecker perches at the  entrance to its nest site in a longleaf pine.(b) Forest that can  sustain red-cockaded  woodpeckers has  low undergrowth.(c) Forest that cannot sustain red-cockaded  woodpeckers has high, dense undergrowth that  impacts the woodpeckers’ access to feeding grounds.Figure 55.13a–cIn a study where breeding cavities were constructedNew breeding groups formed only in these sitesOn the basis of this experimentA combination of habitat maintenance and excavation of new breeding cavities has enabled a once-endangered species to reboundWeighing Conflicting DemandsConserving species often requires resolving conflictsBetween the habitat needs of endangered species and human demandsConcept 55.3: Landscape and regional conservation aim to sustain entire biotasIn recent years, conservation biologyHas attempted to sustain the biodiversity of entire communities, ecosystems, and landscapesOne goal of landscape ecology, of which ecosystem management is partIs to understand past, present, and future patterns of landscape use and to make biodiversity conservation part of land-use planningLandscape Structure and BiodiversityThe structure of a landscapeCan strongly influence biodiversityFragmentation and EdgesThe boundaries, or edges, between ecosystemsAre defining features of landscapes(a) Natural edges. Grasslands give way to forest ecosystems in  Yellowstone National Park.(b) Edges created by human activity. Pronounced edges (roads)  surround clear-cuts in this photograph of a heavily logged rain  forest in Malaysia.Figure 55.14a, bAs habitat fragmentation increasesAnd edges become more extensive, biodiversity tends to decreaseResearch on fragmented forests has led to the discovery of two groups of speciesThose that live in forest edge habitats and those that live in the forest interiorFigure 55.15Corridors That Connect Habitat FragmentsA movement corridorIs a narrow strip of quality habitat connecting otherwise isolated patchesIn areas of heavy human useArtificial corridors are sometimes constructedFigure 55.16Movement corridorsPromote dispersal and help sustain populationsEstablishing Protected AreasConservation biologists are applying their understanding of ecological dynamicsIn establishing protected areas to slow the loss of biodiversityMuch of the focus on establishing protected areasHas been on hot spots of biological diversityFinding Biodiversity Hot SpotsA biodiversity hot spot is a relatively small areaWith an exceptional concentration of endemic species and a large number of endangered and threatened speciesTerrestrial biodiversity hot spotsEquatorFigure 55.17Biodiversity hot spots are obviously good choices for nature reservesBut identifying them is not always easyPhilosophy of Nature ReservesNature reserves are biodiversity islandsIn a sea of habitat degraded to varying degrees by human activityOne argument for extensive reservesIs that large, far-ranging animals with low-density populations require extensive habitatsIn some casesThe size of reserves is smaller than the actual area needed to sustain a populationBiotic boundary forshort-term survival;MVP is 50 individuals.Biotic boundary forlong-term survival;MVP is 500 individuals.Grand TetonNational ParkWyomingIdaho43424140050100KilometersSnake R.Yellowstone National Park Shoshone R.MontanaWyomingMontanaIdahoMadison R.Gallatin R.Yellowstone R.Figure 55.18Zoned ReservesThe zoned reserve model recognizes that conservation effortsOften involve working in landscapes that are largely human dominatedZoned reservesAre often established as “conservation areas”(a) Boundaries of the zoned reserves are indicated by black outlines.(b) Local schoolchildren marvel at the diversity of life in one of  Costa Rica’s reserves.NicaraguaCostaRicaPanamaNational park landBuffer zonePACIFIC OCEANCARIBBEAN SEAFigure 55.19a, bSome zoned reserves in the Fiji islands are closed to fishingWhich actually helps to improve fishing success in nearby areasFigure 55.20Concept 55.4: Restoration ecology attempts to restore degraded ecosystems to a more natural stateThe larger the area disturbedThe longer the time that is required for recoveryWhether a disturbance is natural or caused by humansSeems to make little difference in this size-time relationshipRecovery time (years)(log scale)1041,0001001011031021011101001,000104Natural disastersHuman-caused disastersNatural OR human-caused disastersMeteorstrikeGroundwaterexploitationIndustrialpollutionUrbanizationSalinationModernagricultureFloodVolcaniceruptionAcidrainForestfireNuclearbombTsunamiOilspillSlash& burnLand-slideTreefallLightningstrikeSpatial scale (km2)(log scale)Figure 55.21One of the basic assumptions of restoration ecologyIs that most environmental damage is reversibleTwo key strategies in restoration ecologyAre bioremediation and augmentation of ecosystem processesBioremediationBioremediationIs the use of living organisms to detoxify ecosystemsBiological AugmentationBiological augmentationUses organisms to add essential materials to a degraded ecosystemExploring RestorationThe newness and complexity of restoration ecologyRequire scientists to consider alternative solutions and adjust approaches based on experienceExploring restoration worldwideTruckee River, Nevada.Kissimmee River, Florida.EquatorFigure 55.22Tropical dry forest, Costa Rica.Succulent Karoo, South Africa.Rhine River, Europe.Coastal Japan.Figure 55.22Concept 55.5: Sustainable development seeks to improve the human condition while conserving biodiversityFacing increasing loss and fragmentation of habitatsHow can we best manage Earth’s resources?Sustainable Biosphere InitiativeThe goal of this initiative is to define and acquire the basic ecological information necessaryFor the intelligent and responsible development, management, and conservation of Earth’s resourcesCase Study: Sustainable Development in Costa RicaCosta Rica’s success in conserving tropical biodiversityHas involved partnerships between the government, other organizations, and private citizensHuman living conditions in Costa RicaHave improved along with ecological conservationInfant mortality (per 1,000 live births)200150100500190019502000807060504030YearLife expectancyInfant mortalityLife expectancy (years)Figure 55.23Biophilia and the Future of the BiosphereOur modern livesAre very different from those of early humans who hunted and gathered and painted on cave walls(a) Detail of animals in a Paleolithic mural, Lascaux, FranceFigure 55.24aBut our behaviorReflects remnants of our ancestral attachment to nature and the diversity of life, the concept of biophilia(b) Biologist Carlos Rivera Gonzales examining a tiny tree frog in  PeruFigure 55.24bOur innate sense of connection to natureMay eventually motivate a realignment of our environmental priorities