* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Causes of extinction
Unified neutral theory of biodiversity wikipedia , lookup
Restoration ecology wikipedia , lookup
Biogeography wikipedia , lookup
Occupancy–abundance relationship wikipedia , lookup
Extinction debt wikipedia , lookup
Introduced species wikipedia , lookup
Holocene extinction wikipedia , lookup
Overexploitation wikipedia , lookup
Theoretical ecology wikipedia , lookup
Latitudinal gradients in species diversity wikipedia , lookup
Conservation biology wikipedia , lookup
Assisted colonization wikipedia , lookup
Molecular ecology wikipedia , lookup
Island restoration wikipedia , lookup
Habitat destruction wikipedia , lookup
Biodiversity wikipedia , lookup
Decline in amphibian populations wikipedia , lookup
Biological Dynamics of Forest Fragments Project wikipedia , lookup
Biodiversity action plan wikipedia , lookup
Conservation Biology Chapter 59 1 Biodiversity Crisis • Extinction is a fact of life: all species become extinct eventually • More than 99% of species known to science are now extinct • Current accelerating loss of habitat – 20% of present day species will be extinct by the middle of this century – 2000 of the world’s 8600 species of birds could go extinct 2 Biodiversity Crisis • Members of Homo sapiens wreaked havoc even in prehistoric times • Mammoths and mastodons, giant sloths, saber-toothed tigers • 74% - 86% of mega fauna thought to have been caused by human hunting 3 Biodiversity Crisis • 40,000 years ago Australia had mega sized marsupials – All disappeared at about the same time humans arrived • Madagascar human caused extinctions – 15 species of lemurs – Pigmy hippopotamus – Flightless elephant bird (3m tall), 13 species of moas, and more 4 Biodiversity Crisis Why have African mega fauna survived ? • Perhaps because animals coevolved with humans there • Animals evolved counteradaptations to human predation 5 Biodiversity Crisis • The majority of recent extinctions have occurred in the past 150 years • Increased rate of extinction is worsening • Birds recognized as critically endangered increased from 8% in 1996 to 2000 • Half of Earth’s plant species may be threatened • 2/3rds of vertebrate species could perish by the end of this century 6 Biodiversity Crisis • Majority of extinctions have occurred on islands – 85 species of mammals; 60% lived on islands • Why are islands so vulnerable ? – Evolved in the absence of predators – Humans introduced competitors, diseases – Island populations are usually small which increases their risk for extinction 7 Biodiversity Crisis • Current mass extinctions are notable because – It is the only such event triggered by a single species (Homo sapien) – A few million years is a long time to wait for recovery – It is not clear that biodiversity will rebound this time • Humans are utilizing resources that new species would need to evolve 8 Biodiversity Crisis • Endemic species: species found naturally in only one geographic area and no place else – Occupy restricted ranges – Example: Komodo dragon lives only in a few islands – Example: Mauna Kea Silversword only lives in a single volcano crater on the island of Hawaii 9 Biodiversity Crisis Silversword Some species under imminent extinction threat 10 Biodiversity Crisis Hotspots: areas where species have high endemism and are disappearing at a rapid rate. Red areas are hotspots. 11 Biodiversity Crisis 25 hotspots have been identified Contain nearly half of all terrestrial species in the world 12 Biodiversity Crisis • Human population growth in hotspots • By protecting 1.4% of the world’s land surface – 44% of the worlds vascular plants – 35% of its terrestrial vertebrates can be preserved • In 1995, 20% of the human population were located in hotspots • Growth rate exceeds the average in 19 hotspots 13 Biodiversity Crisis 14 Biodiversity Crisis Why are species going extinct in hotspots ? • High rates of habitat destruction – Land cleared for agriculture, housing, economic development • More than 70% of the original area of each hotspot has already disappeared • Only 15% or less of original habitat remains in 14 hotspots – 90% Madagascar forest lost – 95% Brazilian forest lost 15 Value of Biodiversity • Why care about loss of biodiversity ? – Direct economic value of products we obtain from species: food and drugs – Indirect economic value of benefits produced by species without our consuming them – Ethical and aesthetic values 16 Value of Biodiversity • Direct economic value includes resources for our survival – Food crop genetic variation – 40% of prescription and nonprescription drugs have active ingredients extracted from plants • Aspirin • Cancer fighting drugs 17 Value of Biodiversity • Rosy Periwinkle: vinvlastine and vincristine effectively treat common forms of childhood leukemia – Increase chances of survival from 20% to over 95% 18 Value of Biodiversity Cancer-fighting drugs like taxol, have been developed from the bark of the Pacific yew 19 Value of Biodiversity • Indirect economic value is derived from ecosystem services – Maintain chemical quality of natural water, buffer against storms and droughts – Prevent loss of minerals and nutrients – Moderate local and regional climate – Absorb pollution – Promote breakdown of organic wastes and cycling of minerals 20 Value of Biodiversity Mangroves in Thailand are more Valuable than Shrimp farms 21 Value of Biodiversity Tropical rainforests provide more economic benefits if they are left standing than if they are destroyed and the land used for other purposes 22 Value of Biodiversity Case Study: New York City watershed • 90% of 9 million people’s water comes from the Catskill Mountains and Delaware River • Dilemma: Protect functioning ecosystem or construct filtration plants – To build plants cost $6 billon – Operating cost $300 million/year – Spend $1 billion over 10 years to preserve the ecosystem 23 Value of Biodiversity New York City’s water source 24 Value of Biodiversity • Economic trade-offs – Ecosystem was beneficial when the United States was being settled – Habitat destruction today may be economically desirable • How many services will it provide • What are the negative effects –Increased flooding and pollution –Decreased rainfall –Vulnerability to hurricanes 25 Value of Biodiversity • Consequences of removing a species could mean we are gambling with the future of an ecosystem we depend on • Problems of valuing ecosystems – Do not have a good estimate of the monetary value of services provided by ecosystems – People who gain the benefits of environmental degradation are often not the same people who pay the costs 26 Value of Biodiversity • Ethical and aesthetic values are based on our conscience – Every species has a value of its own – Humans should act as guardians or stewards for the diversity of life around us – How do we place a value on beauty ? • What if it no longer existed ? 27 Value of Biodiversity 28 Factors Responsible • Causes of extinction: direct or indirect – Overexploitation – Habitat loss – Introduced species – Disruption of ecosystem interactions – Pollution – Loss of genetic variation – Catastrophic disturbances 29 Factors Responsible • Case Study: Amphibians on the decline • 1963, Jay Savage Costa Rica – Many breeding toads, bright orange • Bufo periglenes • 1989, only a single male was observed • Today, no toads • They have gone extinct 30 Factors Responsible 31 Factors Responsible • Frogs in trouble – Frog populations that had once been abundant were now decreasing or entirely gone – 2005: 43% of amphibian species experienced decreases in population size – 1/3rd are threatened with extinction 32 Factors Responsible 33 Factors Responsible Why worry about amphibian declines ? 1. Many species have declined in pristine, well-protected habitats 2. Particularly sensitive to the state of the environment because of their moist skin • Chemicals pass into their body • Larval habitats are aquatic 34 Factors Responsible 3. No single cause for amphibian decline is apparent – Different species are afflicted by different problems – Global environment is deteriorating in many different ways 35 Factors Responsible • Habitat loss devastates species richness • Natural habitats may be adversely affected by humans 1. Destruction 2. Pollution 3. Disruption 4. Habitat fragmentation 36 Factors Responsible • Destruction of habitat – Clear-cut harvesting of timber – Burning of tropical forests – Urban and industrial development • 10 fold increase in habitat area leads to ~ doubling in the number of species • Area reduced by 90% then half of all species will be lost 37 Factors Responsible Rain forest covering the eastern coast of Madagascar: • 90% habitat loss • many extinctions • 16 of 31 primate species threatened or extinct 38 Factors Responsible Extinction and Island Area 39 Factors Responsible • Pollution – Species can no longer survive – Aquatic environments particularly vulnerable – Many lakes “sterilized” by acid rain • Disruption – Visitors to bat cave: four visits per month caused 86% - 95% declines in population size 40 Factors Responsible • Habitat fragmentation: dividing the habitat up into small, unconnected areas – Low population numbers – Smaller populations in each fragment – Edge effects: changes in microclimate along the edge of a habitat 41 Factors Responsible • Edge effects – Trees exposed to more sunlight • Hotter and drier conditions • Less biomass growth – Opportunities for parasite and predator species – Habitat fragmentation is blamed for local extinctions in a wide range of species 42 Factors Responsible • Fragmentation of Wisconsin woodland habitat • Cover less than 1% of original area 43 Factors Responsible • Landowners in Manaus, Brazil preserved patches of rain forest of different sizes to examine the effect of patch size on species extinction • Extinction rate was negatively related to patch size • Even the largest patches (100 hectares) lost half of their bird species in less than 15 years 44 Factors Responsible Manaus, Brazil 45 Factors Responsible Case Study: songbird declines • Year round residents prosper (robins) • Migrant songbirds have declined – Nest in northern forests in summer but spend winter in South or Central America or the Caribbean Islands – Rock Creek Park in Washington, DC lost 90% in the past 20 years 46 Factors Responsible • Nation wide, American redstarts declined about 50% in 10 years • Only about has as many birds fly over the Gulf of Mexico each spring as in the 1960’s • Culprit: – habitat fragmentation and loss – Availability of winter habitat declined 47 Factors Responsible American Redstart 48 Factors Responsible Case Study: whales • Over fishing • IWC regulates commercial whale hunting • Was it too late ? 49 Factors Responsible Introduced species threaten native species and habitats • Colonization: process by which a species expands its geographic range – Birds are blown off course – Bird eats a fruit and defecates its seeds miles away – Lowered sea levels connect to isolated populations 50 Factors Responsible • Colonization brings together species with no history of interaction • Ecological interactions may be strong because species have not evolved ways of adjusting to the presence of one another • Results: – Increase in species diversity – Extinction of species 51 Factors Responsible • Human influence on colonization – Plants and animals can be transported in the ballast of large ocean vessels Zebra mussels 52 Factors Responsible • 50,000 species have been introduced in the United States • Effects: – $140 billion per year in economic costs – Human health: west nile fever – Hawaii: mosquitoes brought malaria • 70% native fauna extinct or restricted to high elevations 53 Factors Responsible Two thirds of Hawaiian birds are extinct or have reduced populations 54 Factors Responsible • Effect may not be direct, but spread through the ecosystem – Argentine ant has spread through much of the southern US, reducing populations of native ant species • Negative effect on coast horned lizard which feeds on native ants • Native ants spread seeds, introduced ones do not 55 Factors Responsible • Efforts to combat introduced species – Eradicating extremely difficult, expensive and time consuming – Prevent introduction • Case Study: Lake Victoria cichlids – 300 species of cichlid fishes: most extinct, endangered or threatened – Nile perch introduced in 1954 56 Factors Responsible • How did cichlid extinctions occur? – Eutrophication, algal bloom, cichlid populations increased, oxygen levels dropped – Nile perch populations increased as cichlids populations increased – Nile perch ate many of the cichlids – Introduction of water hyacinth compounded the problem 57 Factors Responsible Disruption of ecosystems can cause an extinction cascade 58 Factors Responsible • Loss of keystone species may disrupt ecosystems – Sea otters are a keystone species of kelp forest ecosystems – Keystone species is a qualitative concept – Flying fox bats are a keystone species • Pollinates plants • Key disperser of seeds • Elimination due to hunting and habitat loss is having a devastating effect 59 Factors Responsible • Small populations are vulnerable to extinction – Demographic factors • Ill-equipped to withstand catastrophes • Heath hen –Once common in US: hunting pressure eliminated all but 1 population –Fire destroyed the preserve’s habitat –Population ravaged by predators 60 Factors Responsible Heath hen and dusky seaside sparrow 61 Factors Responsible • Lack of genetic variability is a second dilemma small populations face – Genetic drift • Populations lacking variation composed of sickly, unfit or sterile individuals • More genetically variable individuals have greater fitness 62 Factors Responsible Case Study: Prairie chickens • Was abundant in midwestern prairies • 1837 introduction of agriculture in the prairies; population has collapsed • 1962 & 1967 sanctuaries established – Privately owned grasslands disappeared – 1990, egg hatching rate only 38% – One dominant male: genetic variation loss 63 Factors Responsible • Tested genetic variation theory – Extracted DNA for stuffed birds collected in 1930s – Compared to birds living in the same place before 1970 population collapse – Genetic variation loss in population in Illinois – Transplant birds from other states – Hatching rates back up to 94% in 1994 64 Factors Responsible Prairie chicken, male mating ritual 65 Preserving Species Destroyed habitats can sometimes be restored • Restore plants and animals to abandoned farm lands • No restoration is ever truly pristine 66 Preserving Species Removing introduced species • Cichlid fishes restoration – Breeding and restocking endangered species – Removal of water hyacinth and Nile perch populations 67 Preserving Species Cleanup and rehabilitation • Clean up pollution • Nashua River in New England – Heavily polluted habitat – Returned to near pristine condition 68 Preserving Species Case Study: Peregrine falcon • DDT banned in 1972 – Captive breeding program began in 1970 – 1986: over 850 birds released in 13 states 69 Conservation of Ecosystems • Habitat fragmentation is one of the most pervasive enemies of biodiversity conservation efforts • Focus on preserving pristine state in national parks and reserves – Amount of land preserved is limited – Not many areas completely protected • Also focus on surrounding areas with some level of human disturbance 70 Conservation of Ecosystems • Key to management – Operate them in a way compatible with local land use • No economic activity in core pristine area • Remainder of land used for nondestructive harvesting of resources • Some hunting • Corridors of dispersal 71 Conservation of Ecosystems • Corridors of dispersal – Link pristine areas – Increase population sizes – Allow recolonization due to catastrophe – Protection to species that move over great distances during the course of a year 72 Conservation of Ecosystems 73