19 - conservation biology
DESCRIPTION
eTRANSCRIPT
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Todayfinish biodiversity (Chapter 23)start conservation biology (Chapter 25)Wednesdayconservation biologyFridayquiz!conservation biologyMondayhistorical biogeography (Chapter 24)Wednesdayecosystem management (outside reading)
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Conservation Biology - a mission-oriented science that focuses on protecting and restoring biodiversity
BiodiversityAll forms of lifeAll levels of organization (subpopulation to biosphere)All interactions among forms of life and the environment
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Where is the biodiversity?
Endemic species restricted to a small regionisolated areas (islands, mountain ranges)product of unique habitat, climate features
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Biodiversity hotspots - areas with a high concentration of endemic species, experiencing rapid habitat loss
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Hotspots:1.4% of the land area44% of vascular plant species35% of terrestrial vertebrate species
But20% of the human population, which isgrowing at 1.8% per year (vs. 1.3% worldwide)each hotspot has already lost 70% of its vegetation
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Current Status of Biodiversity1.4 million described species, possibly 10 million in total
Background extinction rate rate of species loss in the absence of human activitiesfossil record: species survive 1-10 million yearsone year: one species has a 1 in 1-10 million chance of going extincttotal: 1 extinction per year
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Mass extinction loss of large number of speciesusually due to catastrophic volcano or meteor impactvery rare (5 times in 3 billion years)
Current rate of extinction???
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Some estimates for current rate:1 species per hour1 million species total, so far10% of all species so far8.8% of all species27,000 species per year20% of neotropical plant species100 to 10,000 times the background rate
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Numbers of threatened/endagered species:5,188 vertebrates (9%)1,992 invertebrates (0.17%)8,321 plants (2.89%)2 lichens (0.02%)
Since 1600, ~1000 species have gone extinct (probably many more)
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Why do species go extinct?
2 separate processes:Something causes a large population to decline.
Small populations go extinct.
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Causes of species declinesHabitat destruction and fragmentationIntroduced speciesExploitation and overharvestingPollutionClimate change
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USA
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Habitat destruction and fragmentation
Fragmentation disruption of extensive habitats into small, isolated patches
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Relaxation loss of species from isolated habitats over timeAreaS
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Edge effects negative impacts adjacent to habitat boundaries
Forest edges:more sunlightdryinghigh windstree mortalityinvasive speciesmore predators
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Core areaEdge area Core area part of a patch not impacted by edge effects
Patch size is not always the best predictor of patch quality
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Introduced speciesHumans are constantly moving species between continents, islandsdeliberate or accidental
Most serious impacts on islandslow species diversityfew native predatorsanimals lack anti-predator defenses, resistance to diseases
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Characteristics of invasive speciespioneer specieshigh dispersal ratesfound in disturbed habitats, butsome can invade undisturbed communities
Why are invasives successful?no diseases, herbivores, parasites, predatorsbetter competitors than native species
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Introduced diseases exploit lack of evolved resistanceDutch elm disease American elmChestnut blight American chestnutavian malaria Hawaiian birdsRinderpest African ungulateschytrid fungus amphibians
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Net result of invasive specieshomogenize ecological communities around the worlddrive native, endemic species extinct
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Exploitation and overharvestDirect exploitation for foodoverfishingbycatch in fisheries killing non-target species (birds, marine mammals)bush meat harvest of wild animals for foodcan be sustainable, but often notthreatens many large mammals, primates
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Global trade in wildlifebirds, orchids, cactus, primates captured for gardens, pets, zoos, etc.
Many species driven extinct before hunting/harvest regulations were in placepassenger pigeon, island tortoises, marine mammals
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ExamDefinitions, compare-contrast 5 points each (20 points per page)5 questions 12 points per questionbonuses 3 points eachdropped the question with the lowest score
Average grade = 86
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Causes of species declinesHabitat destruction and fragmentationIntroduced speciesExploitation and overharvestingPollutionClimate change
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PollutionMost important for aquatic systemschemical pollutantsacid precipitationBioaccumulation process by which toxin concentrations increase in living tissuesconcentrations increase through the food chain
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Climate change
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Why do small populations go extinct?
Demographic stochasticity chance events that occur at small populations sizefailure to breed or survivefailure to find a mateskewed sex ratio
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Dusky Seaside Sparrow
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Environmental effects unpredictable events that reduce survival or reproductiondroughts, floods, fires, storms
Genetic effects at small population sizeinbreedinggenetic driftrandom mutations
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Extinction vortex combination of genetic, environmental and demographic factors that drive a small population to extinction
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Heath hen1700 throughout the northeast coast1907 50 left on Marthas Vineyard1915 2000 birds1916 fire1917 goshawk invasion1920s poultry disease1927 13 birds, mostly malesMarch 11, 1932 last known sighting
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Minimum viable population smallest population has a specified probability of surviving for a certain timeusually 95% chance of surviving for 100 yearsHow big?at least 50 individuals to avoid demographic stochasticityat least 500 individuals to avoid genetic effectsrealistically > 1000 but varies by species
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Reasons for protecting biodiversity
Intrinsic valuable for its own sake
Instrumental beneficial to humans
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Instrumental Reasons for Protecting BiodiversityEconomic benefitsfooddrugscultivated cropsecotourism
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Ecosystem services quantifiable services that an ecosystem provides to humans often very valuable economically
Examples:moderating climatesmitigating floods and droughtseliminating waste and toxinspest controlpollination
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PollinatorsInsects pollinate 2/3 of crop species~25% of foods consumedU.S.: $20 to 40 billion in agriculture
Evidence that many pollinators are decliningbatshoneybees hummingbirds
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Maintenance of ecosystem functionHow many species can you safely remove?How do you ensure maximum productivity in managed or natural ecosystems?
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More diverse ecosystems are more stable
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Diversity-productivity relationshipHow are plant species richness and primary productivity related?
3 possibilities:
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Why would productivity increase with richness?Greater odds of encountering a super-productive speciesComplementarity use of different resources by different species