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Lecture 7

American University - Washington D.C.
Uploaded: 7 years ago
Contributor: Eels
Category: Conservation Biology
Type: Lecture Notes
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Filename:   Lecture 7.pptx (5.82 MB)
Credit Cost: 7
Views: 277
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Transcript
1Conservation BiologyBIOL3620Lecture 7 Habitat DestructionPrimack Chapter 9 Major Threats to BiodiversityHumans have had impacts on all parts of the earth:Terrestrial (including air), marine, freshwater, FISHERIES ? LEADING TO OVERHARVESTINGHuman activities that have and continue to impact the world:AGRICULTUREHUNTING (TRADITIONALLY)TRADE (IMPORT/EXPORT) ? POSSIBILITY OF INTRODUCING INVASIVE SPECIES AND DISEASESURBANIZATION2 Major Threats to Biodiversity9.3 Citizens of wealthy, developed countries seem unwilling to acknowledge their own excessive consumption3 Major Threats to BiodiversityPrimary threats to biodiversity:Human populationIncreasing consumption levelsHumans don’t aim to destroy - happens as a consequence of our activities which are for the most part not sustainable.Important to look at the big picture9.2 Human population has increased spectacularly since the seventeenth century4 5 Ecological FootprintsIndustrialized countries use disproportionate amount of world’s energy, minerals, wood products and food6 Ecological FootprintsA modern city in a developed country typically has an ecological footprint between 290 – 1130 times it’s areaHere’s a sobering statistic:City of Toronto:Area = 630 km2Each person requires 7.7 to provide food, water, waste disposalPopulation = 2.4 million peopleEcological footprint = 185,000 km2 – an area the size of New Jersey or Syria!!This trend is being adopted in the developing world in nations experiencing fast development (e.g. China and India)increases the probability of massive environmental disruption.7 Seven Major Types of Biodiversity Threats Resulting From Human ActivityHabitat Destruction2. Habitat Fragmentation8 Major Types of Biodiversity Threats3. Habitat Degradation(including global pollution)9 Seven Major Types of Biodiversity Threats Resulting From Human Activity4. Overexploitation5. Global climate change10 Major Types of Biodiversity Threats6. Invasive species11 Major Types of Biodiversity Threats7. Increased Spread of DiseaseAvian Flu12 Figure 9.1 Human activities create multiple threats to biological diversity13Major Types of Biodiversity Threats Habitat Destruction83% of land surface has been transformed by humans.60% of earth’s ecosystems – degraded or unsustainably used.Three to six times more water is held in dams/reservoirs than runs in the world’s rivers.Habitat destruction is the primary cause of loss of biodiversity (including species, biological communities and genetic variation).14 Habitat DestructionFigure 9.4 Threats to the world’s species15 Habitat DestructionImportant to identify the range of impacts, their causes and distribution locally and globally.This understanding allows for:Priorities for actionDevelopment of strategies to counteract and/or slow down degradation.The most important means of protecting biodiversity is habitat preservation16 What Constitutes Habitat Loss/ Degradation?Impacts of habitat change range from:Light and temporary (small fires)…toDevastating and permanent (urbanization)TerminologyHabitat degradationIMPACTS AFFECT MANY BUT NOT ALL SPECIESIMPACTS MAY BE TEMPORARY – ALTHOUGH COULD BE PERSISTENT AT LOW TO MEDIUM LEVELS OF INTENSITY.17 What Constitutes Habitat Degradation?Habitat lossIMPACTS SO SEVEE THAT ALL OR NEARLY ALL SPECIES ARE AFFECTEDEXTREME CHANGES THAT MAKE THE HABIBTIAT UNABALE TO SUPPORT MORE THAN A FRACTION OF ORIGINAL FUNCTION AND SPECIES… ORTIMEFRAME FOR RECOVERY IS VERY LONGShift from habitat degradation to loss – SEEN AS DEGRADTION GROWS SPATIALLY AND IN SEVERITY AND ABILITY TO RECOVER DIMINISHES18 What Constitutes Habitat Degradation?Habitat destruction may not result in total loss of habitat to all species.Reduction in capacity to support a subset of species.FOOD SHELTER, BIOTIC CONDITIONS LESS AVAILABLESURVIVAL, REPRODUCTIVE ABILITY REDUCEDINTERACTIONS BETWEEN SPECIES MAY BE REDUCED19 Figure 9.5 Many of the world’s major biomes have had a large proportion of their area converted to human use20 Frontier forest = intact blocks of undisturbed forest large enough to support all aspects of biodiversity21 Patterns of Habitat Transformation: Forest SystemsLast 300 yrs – half of world’s forests removed for crops, pasture, urbanization.In 25 countries – no forest left.In 29 more countries – 90% of forests lost.Worldwide between 1990 – 2000 proportion of area covered by forest declined (30.4% to 29.7%)38.79 million km2 to 37.85 km2 Translates into a loss of forested area equivalent to the size of Egypt or Columbia.22 Patterns of Habitat Transformation: Forest SystemsTropical moist forests make up 7% of Earth’s surface and contain over 50% of Earth’s species. These species important to local economy (as well as potentially global economy).23 Patterns of Habitat Transformation: Forest SystemsImportance of Forests:Provide many ecosystem services:Regulation of water suppliesMEDIATES FLOW RATES; 2/3 OF THE WORLD DEPEND ON THE WATER THAT PASSES THROUGH FOREST SYSTEMSControl of erosionAffects climateVIA GAS EXCHANGE / EVAPOTRANSPIRATION24 Patterns of Habitat Transformation: Forest SystemsGlobally 60% of rainforest destruction results from small-scale crop cultivation.Shifting cultivation – “slash and burn” or “swidden” agriculture (subsistence farming).TREES CUT DOWN AND BURNED – RESIDUE OF NUTRIENTS LEFT IN ASHCLEARED PATCHES FARMED FOR TWO OR THREE SEASONSSOIL FERTILITY DIMINISHES – ADEQUATE CROP PRODUCTION NO LONGER POSSIBLEPATCHES ABONDONED, MORE LAND CLEARED25 Patterns of Habitat Transformation: Forest SystemsSome rainforest is cleared for fuelwood production – fuel for local villagers.more than two billion people cook with firewood – impact significant.20% of rainforest destroyed via commercial logging.Clear-cutting, selective logging10% cleared for cattle ranches (Latin America)26 Patterns of Habitat Transformation: Forest SystemsLast 5-10% are clear-cut for cash crop plantations:PALM OILCOCOARUBBERLOW-COST WOOD PRODUCTSAlso, for road building and mining.This deforestation often driven by demand for these products by industrialized nations.1980’s – MacDonald’s Hamburgers27 Patterns of Habitat Transformation: Forest SystemsFigure 9.6 Displacement of rain forest for agricultural purposes28 Patterns of Habitat Transformation: Forest SystemsRondônia in Amazonian Brazil (p.183 of text) – good example!29 Patterns of Habitat Transformation: Grasslands, Savanna’s and ShrublandCover 40.5% of Earth’s surfaceNaturally dominated by herbaceous and shrub vegetationMaintained by drought, fire, freezing, grazing by wild ungulates.30 Patterns of Habitat Transformation: Grasslands, Savanna’s and ShrublandTemperate grasslands almost completely destroyed by human activity.Since mid 1800’s – 97% tallgrass prairies and >60% mixed grass and shortgrass prairies lostMOST HEAVILY CONVERTED TO AGRICULURAL LAND AND CATTLE RANCHESALSO, CONVERSION TO URBAN ENVIROMENTS31 Patterns of Habitat Transformation: Grasslands, Savanna’s and ShrublandThese habitats already support large populations of wild ungulates.Contain vast forage for domestic cattle.Problem:Domestic cattle raised to reach high biomassExtensive fencing leads to sedentary habits that:INCREASE SOIL EROSIONCHANGE VEGETATIONELIMINATE MOST VEGETATIVE COVER (EXTREME CASES).32 Patterns of Habitat Transformation: Grasslands, Savanna’s and Shrubland33 Patterns of Habitat Transformation: Wetlands and Freshwater SystemsCritical habitats for fish, aquatic invertebrates and birds.Resource for flood control, drinking water, powerproduction.Some aquatic systemshave high levels of endemism.34 Patterns of Habitat Transformation: Wetlands and Freshwater SystemsFreshwater systems degraded through:WATER DIVERSIONSDAMSWETLANDS LOSSES (2 % OF US RIVERS ARE NOT DIVERTED.Florida EvergladesKatrina disaster (Box 5.1) 35 Patterns of Habitat Transformation: Wetlands and Freshwater SystemsAgriculture and land clearing have increased sedimentation in wetlands and streams.Leads to loss of quality and shift in stream character (fast flowing to slow flowing – different assemblage of species).Agriculture in arid zones drains lake systems.E.g. Aral Sea36 Patterns of Habitat Transformation: Wetlands and Freshwater SystemsAral Sea – KazakhstanShrank 40% in onedecade after usefor irrigation.37 Patterns of Habitat Transformation: Marine SystemsMany populations are reliant on marine resources for food and income.Only just beginning to understand marine habitat degradation.Worst impacts:TOXIC CHEMICALS (OIL SPILLS)SOLID WASTENUTRIENT ENRICHMENT38 Patterns of Habitat Transformation: Marine SystemsFor coastal estuaries, worst impacts:FILLINGDRAININGDREDGINGSHOREINE STABILIZATIONCONVERSION FOR AQUACULTUREAs urban populations grow, coastlines shrink.Loss of freshwater can increase salinity in estuaries.39 Patterns of Habitat Transformation: Marine SystemsMangrovesSub-tropical forestsGrow at interface of land and sea.40 Patterns of Habitat Transformation: Marine SystemsCoral reefsDegraded due to pollution, sedimentation, direct overexploitation, fishing, disease outbreaks (bleaching) – climate change.41 Patterns of Habitat Transformation: Marine SystemsPredicted that extensive areas of coral will be damaged or destroyed in the next 40 years without conservation9.9 Extensive areas of coral will be damaged or destroyed without conservation measures42 DesertificationMany biological communities in seasonally dry climates degraded by human activity become man-made deserts = desertificationThese are not functional desert ecosystemsLack characteristic desert flora and faunaCommunities affected:GRASSLANDSSCRUB AND DECIDIIOS FOREST TEMPERATE SHRUBLANDSFound in Mediterranean, S.W. Australia, S. Africa, central Chile, California43 DesertificationInitially areas support agriculture but repeated cultivation leads to:SOIL EROSIONLOSS OF WATER-HOLDING CAPACITY OF SOILLand may also be overgrazed, harvested for firewoodAlso, frequent fires during long dry periods damages remaining vegetationResult: IRREVERSIBLE DEGRADATION; LOSS OF SOIL COVER44

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