Journal ofthe Bombay Natural HistorySociety, 106(3), Sept-Dec 2009 230-244 THE EXTINCTION CRISIS: FACT OR FICTION? Simon N. Stuart1 'International UnionforConservationofNature(IUCN) Species SurvivalCommission, 1196Gland, Switzerland; UnitedNationsEnvironmentalProgrammeWorldConservationMonitoringCentre,A1AinWildlifeParkandResort,A1Ain, UnitedArabEmirates; andDepartmentofBiology andBiochemistry,UniversityofBath,BathBA27AY, UK. Email: [email protected] Therapiddisappearanceofspecies isoften referredto in a substantial and largely irreversible loss in the diversity asonetheworld’sgreatestenvironmentalconcerns.TheIUCN oflife onearth. Red List ofThreatened Species, which now includes more The structure and function of ecosystems have than44,000animalandplantspecies,showsthatnearlyone- undergone unprecedented changes through the severe quarterofthe planet’s 5,488 mammals and nearly one-third impacts of human activities. Land conversion, habitat of the 6,255 amphibians are globally threatened or extinct. change, pollution, overexploitation, invasive species and Similarly, worrying patterns ofthreatanddecline have been climate change are the direct drivers of threats that are found in other groups, such as birds, reef-building corals, compromisingthecontinuedprovisionofessentialecosystem andgymnosperms. services. TheIUCNRedLististheworld’smostcomprehensive According to the Millennium Ecosystem Assessment informationsourceontheglobalconservationstatusofplant (2005),since 1945,morelandhasbeenconvertedtocropland and animal species. Completed and ongoing assessments than in the 18th and 19th centuries combined. In the last revealthelevelofthreattospecies(highlightingthosefacing severaldecades,20%oftheworld’scoralreefswerelostand a high risk ofglobal extinction) whilst also identifying the a further 20% degraded; there has been a similar impact on — nature and distribution of major threats. Mapping the mangrove areas a 35% loss in the last several decades. distribution of threatened species has identified that the The amount of water in reservoirs has quadrupled, and proportion of threatened species differs markedly between withdrawals fromrivers and lakeshave doubled since 1960. groups and that the pattern ofthreat ofone group does not Transformationshave alsooccurredacrossallofthe world’s predict the pattern ofthreat for another. The distribution of biomes: between 1950 and 1990, 5-10% ofthe area offive threatened species also shows very different patterns biomes had been converted. By 1990, more than two thirds compared with depictions ofoverall diversity. ofthe area oftwo biomes and more than halfofthe area of Numbers of threatened species are increasing across four others had been converted. (Millennium Ecosystem virtually all the major taxonomic groups. There are many Assessment2005). drivers of species extinction, all arising either directly or Increasing human populations have a much greater indirectly from human activities. Overwhelmingly,themost collectiveimpactontheirsurroundingsparticularlywhentheir commonthreatishabitatloss,butover-harvesting,incidental activities lead to excessive volumes of nutrients entering mortality, disease, pollution, and climate change are also ecosystems. The flow ofreactive nitrogen on the continents majorinfluences on the rate ofspecies decline. has already doubled, and some projections suggest that this may increase further by approximately two-thirds by 2050. The Global Context Excessive nitrogen flows have severeenvironmental effects Biodiversity loss is one of the world’s most pressing (eutrophication of freshwater and coastal ecosystems, crises, with many species declining to critically low levels contribution to acid rain, and loss of biodiversity), which and with significant numbers going extinct. Biodiversity is contribute to creation ofground-level ozone, destruction of essential for mankind because many a number of species, ozone in the stratosphere and global warming, all ofwhich andtheecosystemstheyform,providethevastarrayofgoods havesubsequentadverseeffectsonhumanhealth(Millennium and services that sustain our lives. However, despite the EcosystemAssessment2005). immensevalueofbiodiversity,overthepast50yearshumans By the end of the century, climate change and its havechangedecosystems morerapidlyandextensivelythan impacts may be the dominant direct drivers ofbiodiversity in any comparable period of time in human history lossandchangesinecosystemservicesglobally.Thebalance (MillenniumEcosystemAssessment2005).Thishasresulted ofscientificevidencesuggeststhattherewillbeasignificant PaperreadattheInternationalConferenceon ‘ConservingNatureinaGlobalizingIndia’ atBengaluru;February 17-19,2009 THE EXTINCTION CRISIS: FACTOR FICTION? net harmful impact on ecosystem services worldwide, if to population trend, population size and structure, and global mean surface temperatures increase more than 2 °C geographic range (Mace et al. 2008). Species classified as above pre-industrial levels. This would require C0 Vulnerable, Endangered and Critically Endangered are 2 stabilisation at less than 450 ppm (Millennium Ecosystem regardedas ‘threatened’.TheIUCNRedListCriteriacanbe Assessment2005). used to assess the conservation status ofany species, apart The changes that have been made toecosystems have frommicroorganisms. contributedtosubstantialnetgainsinhumanwell-being and The IUCN Red List is compiled and produced by the economicdevelopment.However,oftenthesegainshavebeen IUCN Species Programme based on contributions from a achieved at growing costs. Due to the degradation ofmany network ofthousands ofscientific experts around the world ecosystem services, levels of poverty have remained high, intheIUCNSpeciesSurvivalCommission.Assessmentsare and inequities are growing. It is estimated that 1.1 billion impartial and peer-reviewed, providing objective data to people are surviving on an income ofless than $1 per day, support national, regional and global conservation priority 70% of whom are in rural areas where they are highly setting. It is updated regularly and is freely available The dependent on ecosystem services (Millennium Ecosystem Red List is used for many purposes, as summarised in Assessment2005). Rodrigues etal. (2006) and Vie etal. (2009). Many people are still unable to access an improved One of the IUCN Red List’s main purposes is to water supply, and more than 2.6 billion lack access to highlight those species that are facing a high risk ofglobal improvedsanitation.Waterscarcityaffectsroughly 1-2billion extinction. However, it is not just a register of names and people worldwide and will continue to worsen, as 5% to associatedthreatcategoriesbutitisalsoarich,expert-driven possibly 25% of global freshwater use exceeds long-term compendium of information on species’ ecological accessible supplies. On an average, irrigation withdrawals requirements,geographicdistributions(includingmaps)and exceed 15-35%ofsupplyratesandarethereforeunsustainable threats.TheRedListisusedtodeterminewhatthechallenges (MillenniumEcosystemAssessment2005). to nature are, where they are operating and how to combat Mostdirectdriversofdegradationinecosystemservices them. are growing in intensity in most ecosystems or at best are Byassessingthethreatstatusofspecies,theIUCNRed remaining constant (Millennium Ecosystem Assessment Listhastwogoals: (i)toidentifyanddocumentthosespecies 2005). The result is that we live in an increasingly mostinneedofconservationattentioniftheglobalextinction unsustainable world.Thisis thecontextinwhichweneedto rates are to be reduced, and (ii) to provide a global index of consider biodiversity. We are attempting to achieve the state of change ofbiodiversity. The first ofthese goals conservation in aworldthat is living waybeyondits means, identifies particular species atrisk ofextinction; the second andsotherapidlossofbiodiversity,especiallyatthespecies goalfocusesonusingthedataintheRedListformulti-species level, should not surpriseus. analyses in order to identify and monitor trends in species’ status. TheIUCN Red List Thediversityofspeciesonearthisextraordinary.There It is very important to assess the health ofour global areanestimated8-14millionspeciesinexistence, 1.8million ecosystemsbyprovidingup-to-dateinformationonthe state ofwhichhave been identified and described. The estimates and trends ofwild species. The global tool for doing this is of how much of this diversity is being lost annually are the IUCN Red List of Threatened Species (http:// disheartening, with the number of species assessed as www.iucnredlist.org/). threatened increasing every year. By 2008, 44,838 (2.5%) TheIUCN RedListCategories andCriteria(seehttp:/ species had been assessed (Fig. 1), of which 869 (2%) /www. iucnredlist.org/documents/ have been classified as Extinct or Extinct in the Wild and redlist_cats_crit_en_vl223290226.pdf)arewidelyaccepted 16,928(38%)classifiedasthreatened.Althoughonlyasmall as the most objective and authoritative system available proportionoftheworld’sspecieshadbeenassessedby2008, for assessing the global risk of extinction for species this sample indicates the serious conservation status ofthe (Lamoreux et al. 2003; De Grammont and Cuaron 2006; species looked at so far, how little is still known and how Rodrigues et al. 2006; Mace et al. 2008). Each species urgent the need is to assess more species. assessed is assigned to one of the following categories, Despite the limited number of species assessed in Extinct, Extinct in the Wild, Critically Endangered, relation to the total number of species known, and the Endangered,Vulnerable,NearThreatened,LeastConcernand significant numberofData Deficient species included in it, DataDeficient,basedonaseriesofquantitativecriterialinked the RedListisstill thelargestdatasetofcurrent information J. Bombay Nat. Hist. Soc., 106 (3), Sept-Dec 2009 231 THE EXTINCTION CRISIS: FACTORFICTION? 11% Fig. 1: Numberofspecies appearingon each published IUCN Red Listsince 2000 Fig. 2:The status ofAmphibians by IUCN Red Listcategories EX=Extinct; EW=ExtinctintheWild;CR=CriticallyEndangered; EN = Endangered; VU = Vulnerable; NT = Near Threatened; ontheconservationstatusofspecies.Completedandongoing LC = LeastConcern; DD = Data Deficient assessments include the following: BirdLife International bird assessments (updated 5 times since 1988); Global Mammal Assessment (completed in 2008, now being Statusofbirds updated);GlobalAmphibianAssessment(completedin2004, BirdsarethebestknowntaxonomicgroupontheIUCN now being updated); Global Marine Species Assessment Red List. Since 1988, there have been 5 comprehensive (ongoing); Global Freshwater Biodiversity Assessment assessmentsofbirds, withthemostrecentassessment, ofall (ongoing);andGlobal ReptileAssessment(ongoing).There 9,990 known species, being completed in 2008. Less than arevariousplantandterrestrialinvertebrateassessmentsthat 1% of bird species on the 2008 IUCN Red List have have also started and which are gathering speed. insufficient information available to be able to assess them beyond DataDeficient. STATUS OFTERRESTRIAL BIODIVERSITY Comprehensiveassessments,coveringeveryspeciesin ataxonomicgroup,havenowbeencompletedforamphibians, birds, mammals, cycads and conifers, warm water reef- forming corals, freshwater crabs and groupers. They are almost complete for sharks and rays, mangroves and sea grasses. StatusofAmphibians Nearly one-third of the amphibian species (32.4%) aregloballythreatenedorextinct,representing2,030species (Fig. 2). Thirty-eight species out ofthese 2,030 species are considered to be Extinct (EX), one is Extinct in the Wild (EW). Another 2,697 species are not considered to be threatenedatpresent,beingclassifiedintheIUCNCategories of Near Threatened (NT) or Least Concern (LC), while sufficient information was notavailable to assess the status Fig. 3: Thestatusofbirds by IUCN Red Listcategories of an additional 1,533 species (Data Deficient (DD). It is EX=Extinct; EW=ExtinctintheWild;CR=CriticallyEndangered; predicted that a large proportion of these Data Deficient EN = Endangered; VU = Vulnerable; NT = Near Threatened; species are likely to be globally threatened. LC = LeastConcern; DD= Data Deficient 232 J. Bombay Nat. Hist. Soc., 106 (3), Sept-Dec 2009 THE EXTINCTION CRISIS: FACTOR FICTION? It is clear, however, that being well-studied does not STATUS OF FRESHWATER BIODIVERSITY provide immunity from decline and high extinction risk. Morethan 1 in8birdspecies(13.6%)aregloballythreatened IUCN is working with a number of partner or extinct, representing 1,360 species (Fig. 3). Of these, organisationstofilltheinformationgaponfreshwaterspecies. 134species(1%)areextinct,4speciesnolongeroccurinthe Thisisbeingaccomplishedbyconductingassessmentsofall known species within the following priority groups: wild, and a further 15 are Critically Endangered species flagged as ‘possibly extinct’, making a total of 153 bird freshwater fishes, freshwater molluscs, dragonflies and damselflies, freshwater crabs and selected aquatic plant extinctions since the year 1500. families. With the exception of the crabs, none of these Although8,564bird species(85.7%) arecurrentlynot consideredthreatened,835ofthese(8.4%ofallknownbirds) assessmentsisyetcomplete globally. There have, however, been some comprehensive are NearThreatened; the remaining 7,729 species are Least regionalassessments,inwhicheverydescribedspeciesfrom Concern. a taxonomic group within a region has been assessed. This Statusofmammals hasenabledtheidentificationofriverorlakebasinscontaining Themammal dataonthe2008 IUCNRedListinclude the highest levels of species richness, threatened species, 5,488 species, 412 subspecies and 21 subpopulations. The restricted range species, migratory species and/or species important to the livelihoods oflocal communities. primary focus is, however, at the species level. This is the second time that all mammals have been assessed, the first Thefreshwaterassessmentscompletedforeasternand southern Africa have identified lakes Malawi and Victoria, being in 1996 (Baillie and Groombridge 1996). Of the 5,487 mammal species assessed, nearly one- the lower Malagarasi drainage (Tanzania), the Kilombero Valley(Tanzania)andtheSouthwesternCape (SouthAfrica) quarterofspecies(22.2%)aregloballythreatenedorextinct, as containing some of the highest numbers of threatened representing 1,219 species (Schipper et al. 2008) (Fig. 4). Seventy-sixofthe 1,219speciesareconsideredtobeExtinct species (Fig. 5). (EX),and2ExtinctintheWild(EW).Another3,432species arenotconsideredtobethreatenedatpresent,beingclassified in the IUCN Red List categories ofNT or LC, while there wasinsufficientinformation available toassess the status of an additional 836 species (DD). f M X « Numberofspecies 0 7-13 14-24 25-49 — 0t 25i0 50i0 1.0i0K0ilometers Source:IUCN Fig. 4: The status of mammals by IUCN Red Listcategories EX=Extinct; EW=ExtinctintheWild;CR=CriticallyEndangered; Fig. 5: Distribution patternsof regionallythreatened speciesfor EN = Endangered; VU = Vulnerable; NT = Near Threatened; freshwaterfishes, molluscs, odonates (dragonfliesand LC = LeastConcern; DD = Data Deficient damselflies) andcrabsacross eastern and southernAfrica J. Bombay Nat. Hist. Soc., 106 (3), Sept-Dec 2009 233 THE EXTINCTION CRISIS: FACTOR FICTION? Freshwaterbiodiversityisbeingthreatenedbyanumber ofkey impacts, including overexploitation, waterpollution, river flow modification (including water abstraction), destruction or degradation of habitats, and invasion by invasive alien species (Millennium Ecosystem Assessment 2005; Dudgeon etal. 2006). Compounding these threats are the predicted global impacts of climate change leading to temperature changes and shifts in precipitation and runoff patterns (Dudgeon etal. 2006). Usingfreshwaterfishesasanexample,beingoneofthe mostwidelyassessedofthefreshwaterspeciesgroups,thelevel, nature and distribution of major threats can be identified. Oftheregionsassessedsofar,theMediterraneanandMalagasy endemic freshwater fish are shown to have the highest proportionsofgloballythreatenedspecies,withmorethan50% Fig. 7: Summaryof2008 Red Listcategories ofspeciesthreatenedineachcase,andsouthernAfricatohave forcompletedcladesofmarinespecies thelowestproportion,with 17%ofspeciesthreatened(Fig.6). Numberofspeciesassessed in each group in parentheses [black=EX; red=CFVEN/VU; yellow=NT; green=LC; grey=DD] THE STATUS OF MARINE BIODIVERSITY corals, (seabirds, marine mammals and marine turtles). Work onthesharksandraysisnearingcompletion.Theoverallresults Inrecentyears, there hasbeengrowingconcern inthe of these assessments (including the preliminary results for scientific community that a broad range of marine species sharks andrays) are shown inFig. 7. could be under threat of extinction and that marine The threat status of the different taxonomic groups biodiversityisexperiencingpotentially irreversible loss due variesquitewidely. Overfishingandincidentalmortalityare tooverfishing, climate change, invasive species and coastal particularcommonthreatsinthesea.However,withthereef- development(RobertsandHawkins 1999;Dulvyetal.2003). building corals, the situation is significantly different, as In 2006, IUCN, Conservation International and Old describedbelow. DominionUniversityinitiatedanambitiousproject(theGlobal The world’s known 845 species of reef-building Marine Species Assessment) to complete IUCN Red List zooxanthellate corals (Order Scleractinia plus the families assessmentsforagreatlyexpandednumberofmarinespecies. Helioporidae,Tubiporidae and Milleporidae) were assessed ItisplannedtocompleteRedListassessmentsforover20,000 forthefirsttime(Carpenteretal. 2008).Thesereef-building marinespeciesby2012.Muchprogresshasalreadybeenmade, corals provide the essential habitat formany species offish and approximately 1,500 marine species have been added to andinvertebrates,makingthemthemostbiologicallydiverse the 2008 Red List. IUCN has now assessed all ofthe world’s ecosystemsintheocean.Morethanone-quarterofthesecorals known speciesofsharksandrelatives, groupers,reef-building (27%)havebeenlistedinthreatenedcategories,representing anelevatedriskofextinction. Over20%ofspeciesarelisted as Near Threatened and are expected to join a threatened category in the nearfuture. The primary threat to these reef-building corals is the increasedfrequencyanddurationofbleachinganddiseaseevents that have been linked to the increase in sea temperatures, a symptomofglobalclimatechange(Carpenteretal.2008).These impacts are further compounded by anthropogenic threats, includingcoastaldevelopment,coralextraction,sedimentation and pollution. Another further threat to corals is ocean acidification as a result of increasing levels of atmospheric %ofspecies carbon dioxide. This is reducing ocean carbonate ion concentrationsandtheabilityofcoralstobuild skeletons. Fig. 6: Proportionsoffreshwaterfish speciesbythreatcategory in each ofthe regionsassessedcomprehensively. Globally,theIndo-Malay-PhilippineArchipelagoorthe Onlyspeciesendemictoeach region are included ‘CoralTriangle’hasbyfarthehighestnumberofcoralspecies, 234 J. Bombay Nat. Hist. Soc.( 106 (3), Sept-Dec 2009 THE EXTINCTION CRISIS: FACTOR FICTION? Percentage threatened species Source: IUCN 4.8 14 18 25 60 100 Fig. 8: Mapshowingthe percentagesofthreatened reef-building coral species acrossthe world and also high percentages in threatened categories (Fig. 8). these two groups are markedly different in South America. This region is also known as the epicentre of marine Although nearly one-third of amphibians are at risk, biodiversityandhasthehighestcoralspeciesrichness.Coral threatenedamphibiansarefoundtobeconcentrated in afew reefsin theCaribbeanregionhave beenimpactedbyrecent, areas only, especially in Mesoamerica, the northern Andes rapid population decline of 2 key species: Staghorn Coral andtheGreaterAntilles. Conversely,mostpartsoftheworld AcroporacervicomisandElkhomCoralAcroporapalmata, have at least 1 threatened bird species, despite the fact that both ofwhich have been listed as Critically Endangered. In only 12% ofbirds are threatened. any region, the potential loss ofthese coral ecosystems will have huge cascading effects for reef-dependent species and LOOKINGAT A FINER SCALE for the large number of people and nations that depend on coral reefresources foreconomic and food security. The Red List criteria were developed for use at the globalscale,atwhichtheentiregeographicrangeofaspecies GLOBALTHREAT PATTERNS is considered. However, IUCN is increasingly undertaking regional Red List projects. Regional and national lists are Closerexaminationofsomeofthesetaxonomicgroups usually country-led initiatives and are notcentralised in any reveals interesting patterns inthegeographicconcentrations way; they differ from each other widely in terms of scope ofthreatened across the globe. Fig. 9 shows the geographic and quality but can be very useful in guiding conservation patterns generated from overlaying the distributions of all work at subglobal levels. threatened species in 4 taxonomic groups (birds, mammals, In the Mediterranean region, for example, IUCN has amphibiansandcorals).Thecontrastbetweenthetaxonomic assessedtodatethefollowingtaxonomicgroups: amphibians, groups demonstrates that geographic patterns of threat for reptiles, birds, mammals, sharks and rays, freshwater crabs one group do not predict the patterns of threat for another andcrayfish,endemicfreshwaterfishes,anddragonfliesand group; hence the importance ofassessing the statusofmany damselflies(hereafterreferredtocollectivelyasdragonflies). groups ofspecies. Overall, the proportion of threatened species in the Thereareimportantconcentrationsofthreatenedbirds Mediterranean (those classified as Critically Endangered, and mammals in South-east Asia, but the threat patterns of Endangered or Vulnerable), either at the global or regional J. Bombay Nat. Hist. Soc., 106 (3), Sept-Dec 2009 235 THE EXTINCTION CRISIS: FACTOR FICTION? Threatened coral richness 1 26 58 98 143 176 Source: IUCN Red List ofThreatened Species RL Categories: Vulnerable(VU), Endangered (EN), Critically Endangered(CR) TOHfETIVUWCENATREENDELDISSTHOES' Fig. 9: The geographic patterns generatedfrom overlayingthe distributionsofallthreatened species in fourtaxonomicgroups (birds, mammals, amphibiansandcorals) level, is about one-fifth (19%), and about 1% ofthe species to identify key regions and taxa that require greater are already extinct in the region. These percentages will be conservationattention. higherifsomeofthe currently DataDeficient speciesprove Thisapproachtakesarandom sampleof 1,500species to be threatened, as is likely tobe the case. fromdifferenttaxonomicgroups(Baillieeta/. 2008).Itallows Freshwater species have been mapped based on river theidentificationofthegenerallevelofthreattoeachgroup, basins flowing into the Mediterranean Sea and adjacent the mapping of areas likely to contain the most threatened AtlanticOceanriverbasins. Fig. 10indicatesconcentrations species and the identification ofthe main drivers ofthreats ofspecies at risk, in particular in the Iberian Peninsula, the and helps pinpoint what key actions are required to address Balkans,thewesternpartofGreeceandtheareafromTurkey declines in the group as awhole. down to Israel and the Palestinian territories. The results of both the comprehensive and sampled assessments are starting to provide new insights into our BROADENINGTHE COVERAGE OF understandingofthestatusoftheworld’sspeciesthatcanbe BIODIVERSITYASSESSMENTS built upon to track changes over time. The current plans to expandthenumberofspeciesassessedfortheRedList,using A new initiative is being employed to broaden the both comprehensive and sampled techniques, will, when taxonomiccoverageoftheIUCN RedListinordertoenable implemented, increase the numberofassessed species from a better understanding ofbiodiversity status as a whole and 45,000 (on the Red List in 2008) to 1,30,000 (Fig. 11). 236 J. Bombay Nat. Hist. Soc., 106 (3), Sept-Dec 2009 THE EXTINCTION CRISIS: FACT OR FICTION? Fig. 10: Species richnessofthreatenedfreshwateramphibians, crabs, endemicfishes, mammals, dragonflies and reptiles inthe Mediterranean basin ThefirstresultsofthesampledapproachtoRedListing BIODIVERSITY are now becoming available, specifically for reptiles and fishes, forneitherofwhich the comprehensive assessments Vertebrates Invertebrates Plants are complete yet. Across reptile groups, for example, the IE proportionofspeciesthreatenedvaries: 43%ofcrocodilians f ^ 1 ^ are threatened, compared with 12% of snakes and 20% of Mammals Ants Bryophytes Birds Butterflies Pteridophytes lizards. These patterns are likely to reflect differences in Reptiles Dragonflies Gymnosperms geography,rangesize,habitatspecificityandbiology,aswell Amphibians Freshwater Molluscs Monocots as threat intensity. Indo-Malaya is the most species-rich Fishes Freshwater Crabs Angiosperms biogeographic realm forreptiles, and it also has the greatest Sharks Reef-forming Corals ^ Fungi y density ofthreatened (CR, EN andVU) species (Fig. 12). t Dung Beetles Crayfish & Lobsters There are also some early results from this sampled Cephalopods J approach for invertebrates. A map of the distribution of threatened freshwater crabs and dragonflies reveals some centres of threat for freshwater systems (Fig. 13). Marked Fig. 11: Overview of IUCN Red Listassessments: comprehensivelyassessed by2008 (black); concentrations of threatened species exist in Vietnam, comprehensiveassessments underway(red); Thailand,Cambodia,MalaysiaandthePhilippinesinSouth- statistically random samples planned orunderway(green) eastAsia; Sri Lanka and the Indian Western Ghats in South Asia,andColombiaandMexicoincentralandSouthAmerica. the long list of unique species that have been lost forever. These patterns are heavily influenced by the distribution of Understanding the extent of recent extinctions provides restrictedrange species. insights into historic extinction rates, which in turn can be compared to the rates over geological time to determine if EXTINCTIONS current trends are normal or acause forconcern. An insight into the process of extinction can help us identify species The global extinction of a species usually represents that are at a risk of extinction and enable us to highlight an end point in a long series of population extinctions. taxonomicgroupsorspeciesfromspecificregionsthatareor Creating an inventory of recent extinctions helps highlight will be particularly prone toextinction. J. Bombay Nat. Hist. Soc., 106 (3), Sept-Dec 2009 237 THE EXTINCTION CRISIS: FACTOR FICTION? ) 0^ Proportion of species assessed as tmhreatened Source: ZSL& IUCN 0.11 0.12 0.33 1 Fig. 12: Threatened species richness mapforreptiles, based on a random sampleof 1,500 species, 244ofwhich arethreatened a timm - -%' > . Proportion of species assessed as threatened Source: ZSL& IUCN ™ ^^ ^^^ T 0.02 0.08 0 28 0 . Fig. 13:Threatenedspecies richness mapforfreshwatercrabs (n =210species), anddragonfliesanddamselflies (n= 136species) 238 J. Bombay Nat. Hist. Soc., 106 (3), Sept-Dec 2009 THE EXTINCTION CRISIS: FACTOR FICTION? o <*> o # • cP • • Reptiles • Mammals • Birds • Amphibians o Molluscs Fig. 14: The distribution of Extinctand Extinct in theWild reptiles, mammals, birds, amphibians and molluscs The world’s list ofdocumented extinctions continues degradation and conversion (resulting in particular from to rise. The 2008 Red List includes 804 species listed as agriculture, logging and residential and commercial Extinct and 60 Extinct in theWild. In the last 24years there development), overexploitation, invasive species, pollution havebeen29documentedextinctions,withrecentextinction and, increasingly, climate change (Figs 16, 17, 18). rates exceeding those from fossil records. With current Habitat loss and degradation are by far the greatest extinction rates 100to 1,000times the natural (background) threattoamphibiansatpresent(Fig. 16),affectingnearly61% extinction rates, it is likely that the world is experiencing a of all known amphibians (nearly 4,000 species), including net loss of species, perhaps for the first time in millions of 87% of the threatened amphibian species. The next most years (Baillie etal. 2004). common threat to amphibians is pollution, which affects There are major differences in the extinction patterns aroundone-fifth(19%)ofamphibianspeciesoveralland29% between the five taxonomic groups mapped in Fig. 14. Bird of threatened species. Although disease is a less common extinctions are overwhelmingly biased towards oceanic threat, it is much more likely to make a species globally islands (including New Zealand), whereas the largest threatened (Fig. 16). Indeed, the fungal disease concentration of mammal extinctions is in Australia. DocumentedamphibianextinctionsarefocusedonSriLanka, but this might be an artefact ofunder-recording extinctions elsewhere. Mollusc extinctions are concentrated in North Americanriversystems,possiblyanotherrecordingartefact. Adetailed examination ofbird extinctions since 1500 A.D. indicates that the pattern ofextinctions might be changing. Although more than 80% ofbirds are found on continents, allextinctionspriorto 1800occurredonislands.Thispattern has started to change in recent years, with more extinctions occurring on continents (Fig. 15). THREATS Year The major processes threatening species and driving Fig. 15: The numberof bird extinctionsthat have occurred extinctionsareallofanthropogenicorigin,andincludehabitat on islandsand continentssince 1500A.D. J. Bombay Nat. Hist. Soc., 106 (3), Sept-Dec 2009 239