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1 Threats to Global Threats to Global Biodiversity Biodiversity We wish to know: What is biodiversity? Why is it important? What are the threats to biodiversity? How can we estimate rates of species loss?

Threats to Global Biodiversity

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Threats to Global Biodiversity. We wish to know: What is biodiversity? Why is it important? What are the threats to biodiversity? How can we estimate rates of species loss?. What is Biodiversity?. - PowerPoint PPT Presentation

Text of Threats to Global Biodiversity

  • Threats to Global BiodiversityWe wish to know:What is biodiversity? Why is it important?What are the threats to biodiversity?How can we estimate rates of species loss?

  • What is Biodiversity?the variety and variability among living organisms and the ecological complexes in which they occurnumber and variety of species, ecological systems, and the genetic variability they contain.In its narrowest sense biodiversity refers to the number of species on the planet

  • How Many Species Exist?Some 1.4 to 1.8 million species are "known to science" -- meaning that they have been classified by a specialistMost experts estimate the world's species diversity at 10 to 30 million, but that is very approximateExcept for land vertebrates and flowering plants, the number of undescribed species greatly exceeds the number described

  • New DiscoveriesPsudoryx nghetinhensis, recently discovered in north-central Viet Nam.is really two, such as this Australian mountain brushtail possum, or the recent splitting of the African elephant into a savannah and forest species.Ichthyologists describe about 300 new fish species each yearLess uncommon is the discovery that one speciesDiscovery of a new large mammal is noteworthy.

  • Number of Known, Living, SpeciesAmong species known to science, the diversity of insects is overwhelming in number. For this reason, most animal species live on land, but more phyla, the highest level of classification, live in the sea.~ 1.8 million species

  • Number of Animal Species Currently Known

  • Number of Known Species of Higher PlantsPlant diversity of the world consists primarily of the flowering plants (angiosperms), which are divided into the grasses and other monocots, and a great variety of dicots. Most flowering plants live on land; algae prevail in the sea.

  • What is the real number of living species? 10 million +

  • How do we know that?More than 70% of the species living in a tropical forest reside in the canopy, the uppermost layer of the forest, and one of the least understood environments on EarthThe Smithsonian Tropical Research Institute (STRI)From Didham and Fagan

  • ExtinctionFive great extinctions440 mya, 370 mya, 245 mya (Permian), 210 mya, 65 mya (K-T)Followed by adaptive radiationsThe sixth extinctionPhase 1: began 100,000 years ago with spread of humansPhase 2: began 10,000 years ago with dawn of agriculturePhase 3: began 250 years ago with industrial and scientific revolutionshttp://www.actionbioscience.org/newfrontiers/eldredge2.html

  • ExtinctionDefinition: The end of a phyletic line without phyletic replacementFive levels of extinctionExtinction of a species from almost all of its rangeExtinction of a whole speciesExtinction of groups of lower taxonomic rankExtinction of groups of higher taxonomic rankMass extinction (Many groups in an epoch)

  • Examples of ExtinctionLevel 1American Bison-Estimated 50 million animals prior to European settlement - 541 left by 1889White rhino - Common species in southern Africa nearly extinct by 1894. Now stable in South Africa, but extinct in Uganda, CAR, Zaire, SudanBlack rhino - Four subspecies virtually extinct and predicted to go extinct in next few years, other three are listed as vulnerable

  • Examples of ExtinctionLevel 2 - Whole speciesIrish elk - Went extinct 11,000 years ago, probable cause was change in habitat, although cause is debatedStellers sea cow - Member of order Sirenia that went extinct from overhunting by the 1800s.Level 3 - Genera and familiesSaber-toothed cats - Extinct in Pleistocene. Likely from loss of prey, but possibly overspecialization.

  • Examples of ExtinctionsLevel 4-Phyletic groups11,000 years ago 2/3 of Americas mammals over 100 lbs. were lost rivaling the dinosaur extinctions. Over 100 genera, 36 of 45 families and 9 of 12 orders went extinctSouth America, Australia, and North America lost 70% of megafauna, while Africa lost 20%Level 5 Mass extinctionsSee previous lecture

  • The Pleistocene ExtinctionClimate changeOver-killThe combination

  • Modern Threats to biodiversityHuman actions now threaten species and ecosystems to an extent rarely seen in earth history.The Sextet of threats:Over-harvestExotic speciesHabitat lossClimate changePollution Domino effects

  • Over-ExploitationHunting, especially commercial hunting and poaching, has driven many species to extinction.Passenger pigeon for meat, snowy egret for fashion, rhinos for their horns.Bushmeat harvest is a crisis of tropical forests today

  • Over-ExploitationImagine a tropical parrot inhabiting Michigan?The Carolina parrot, once abundant in eastern N. America, now extinct

  • Bushmeat tradeFor the tropical forests of central and west Africa (the Congo Basin rainforests), greatest threat to vertebrate species is over-hunting for subsistence and commerceFor people living in these areas, up to 90% of total animal protein may be derived from wild animals

  • Invading speciesNon-indigenous species (invaders) often are more effective predators or competitors, thereby eliminating native species. Island (and lake) species may be especially vulnerable.Some of Victoria cichlids

  • Michigan invadersThe gypsy moth arrived in the U.S. in the early 1900s, and in Michigan in the 1950s. With few natural enemies, it devours the leaves of forest trees. Although some defoliation is tolerable, if in two successive years and coupled with a drought, trees can be killed.

  • Michigan invadersThere is little doubt that the sea lamprey was primarily responsible for decline of lake trout in upper Great Lakes (Coble et al. 1990). This is evidenced by the timing of the collapse, coincidence of wounds and scars, simultaneous collapse in unfished bays, and continued decline after fishing had fallen to low levels. Detailed analysis of catch and effort data provided no support for over-fishing as the cause of declines, except in Lake Superior.

  • Winning the War against Invaders

  • Global deforestationOriginal tropical forest extent was ~ 15 m km2; today it is about 8 m km2. At present rates of loss, ~ 10% of the original tropical forests will remain by end of 21st century.

  • Habitat Fragmentation

  • Habitat Fragmentation and Extinction RiskForest fragments in Warwickshire, England, from 400-1960Habitat loss often is accompanied by habitat degradation and habitat fragmentation. Remnant populations persist at very low densities

  • Under a 2 x CO2 scenario, the bobolinks habitat would shift northwardsGlobal Warming

  • Domino Effects

  • Studies of plant and animal biogeography have established a log-linear relationship between number of species in an area, and areal extent. An example for the reptiles and amphibians for the Caribbean is shown with the area axis reversed, to illustrate that reduction in area leads to a reduction in species.Species-Area Relationshipsz = slope

  • Estimating Rates of Species LossThe relationship between number of species and area of habitat is S = c A zthe rate of loss of tropical forest from satellite imagery is 1-2% annuallythe resulting loss rate of species results in an overall loss of 25 - 50% of the worlds species by 2100Assuming tropical forests harbor 10 million species, this loss is 27,000/yr (and 3/hr)

  • Historical vs present-day extinctions

  • How much biodiversity will remain in 2100?

  • hotspot designation: A terrestrial biodiversity hotspot is an area that has at least 0.5%, or 1,500 of the worlds ca. 300,000 species of green plants, and that has lost at least 70% of its primary vegetation. (Current total = 34)http://www.biodiversityhotspots.org/xp/Hotspots

  • SummaryBiodiversity refers to the number and variety of species, of ecosystems, and of their genetic variationAbout 1.4-1.8 million species are known to science. Because many species are undescribed, some 10-30 million species likely exist at presentBiodiversity is threatened by the sinister sextetHabitat loss represents the single biggest threat, along with invasive species. Over-harvest and climate change also are significant.



    Overkill63 of 4,200 mammals and 88 of 8,500 birds

    silent forests of central/west Africa little remaining wildlifeBush hog (left, top center), some kinda rodent?

    Habitat destructionHabitat is lost each year equivalent to W. Virginia

    Distant past refers to average extinction rates as calculated from the fossil record. Recent past refers to extinction rates calculated from known extinctions of species (lower estimate) or known extinctions plus possibly extinct species (upper bound). A species is considered to be possibly extinct if it is believed to be extinct by experts but extensive surveys have not yet been undertaken to confirm its disappearance. Future extinctions are model-derived estimates using a variety of techniques, including species-area models, rates at which species are shifting to increasingly more threatened categories, extinction probabilities associated with the IUCN categories of threat, impacts of projected habitat loss on species currently threatened with habitat loss, and correlation of species loss with energy consumption.

    The outer circle in the Figure represents the present level of global biodiversity. Each inner circle represents the level of biodiversity under different value frameworks. Question marks indicate the uncertainties over where the boundaries exist, and therefore the appropriate size of each circle under different value frameworks.