Conservation of oceanic island floras: Present and future global challenges

Abstract

Currentthreatstotheplanet’sbiodiversityareunprecedented,andtheyparticularlyimperilinsular floras.Inthisinvestigation,weusethethreatfactorsidentifiedbytheMillenniumEcosystem Assessmentasthemaindriversofbiodiversitylossonislandstodefineandrank13current,continuing threatstotheplantdiversityofninefocalarchipelagoswherevolcanicorigin(orintheSeychellesa prolongedisolationafteracontinentalorigin)hasproducedahighdegreeofendemicityandfragilityin the faceofhabitatalteration.Wealsoconductaglobalendangermentassessmentbasedonthe numbersofinsularendemicplantsintheendangered(EN)andcriticallyendangered(CR)IUCN categoriesfor53islandgroupswithanestimated9951endemicplantspecies,providinga representativesampleoftheworld’sinsularsystemsandtheirfloristicrichness.Ouranalysesindicate that isolationdoesnotsignificantlyinfluenceendangerment,butplantendemicsfromverysmall islandsaremoreoftencriticallyendangered.Weestimatethatbetween3500and6800oftheestimated 70,000 insularendemicplantspeciesworldwidemightbehighlythreatened(CR+EN)andbetweenca. 2000 and2800ofthemincriticaldangerofextinction(CR).Basedontheseanalyses,andona worldwideliteraturereviewofthebiologicalthreatfactorsconsidered,weidentifychallenging questionsforconservationresearch,asking(i)whatarethemosturgentprioritiesfortheconservation of insularspeciesandfloras,and(ii)withtheknowledgeandassetsavailable,howcanweimprovethe impactofconservationscienceandpracticeonthepreservationofislandbiodiversity?Ouranalysis indicatesthatthesynergisticactionofmanythreatfactorscaninducemajorecologicaldisturbances, leadingtomultipleextinctions.Wereviewweaknessesandstrengthsinconservationresearchand managementintheninefocalarchipelagos,andhighlighttheurgentneedforconservationscientiststo shareknowledgeandexpertise,identifyanddiscusscommonchallenges,andformulatemulti- disciplinaryconservationobjectivesforinsularplantendemicsworldwide.Toourknowledge,thisisthe mostup-to-dateandcomprehensivesurveyyettoreviewthethreatfactorstonativeplantsonoceanic islandsanddefinepriorityresearchquestions