topic 6: dealing with invasive species: sharing knowledge and experience

A Sense of Direction: a conference on conservation in UK Overseas Territories and other small island communities, page 257

Topic 6: Dealing with invasive species: sharing knowledgeand experience

Workshop co-ordinated by: Oliver D. Cheesman, CABI Bioscience; Colin Clubbe,Royal Botanic Gardens, Kew; Anne F. Glasspool, Bermuda Zoological Society; andKaren Varnham

Cheesman, O., Clubbe, C., Glasspool, A. & Varnham, K. 2003. Dealing withinvasive species: sharing knowledge and experience. pp 257-272 in A Sense ofDirection: a conference on conservation in UK Overseas Territories and other smallisland communities (ed. M. Pienkowski). UK Overseas Territories ConservationForum, www.ukotcf.org

Invasive species are now widely regarded as the second most important threat tobiodiversity, after habitat destruction. The impacts of invasive species are particu-larly severe on small island ecosystems. This paper briefly reviews the importanceof such ecosystems and the threats that they face from invasive species. Someresources available internationally to help in the battle against invasive species(particularly on small islands) are listed, and the outputs of a panel-guided discus-sion are provided in table form. These draw on the knowledge and experience ofconference delegates, under three broad headings: awareness raising, preventionstrategies, and control measures.[Note that some papers relating to this topic occur also earlier in these Proceedings.]

Dr Oliver D. Cheesman, CABI Bioscience, Bakeham Lane, Egham, Surrey, TW209TY, UK [email protected] Colin Clubbe, Royal Botanic Gardens, Kew, Richmond, Surrey, TW9 3AB, [email protected] Annie Glasspool, Bermuda Zoological Society, Bermuda [email protected] Karen Varnham, Invasive Species Biologist, 4 Berkley Court, Shutta, EastLook, Cornwall, PL13 ILU, UK [email protected]

Workshop in session, led by (L to R): Oliver Cheesman, Annie Glasspool, Karen Varnham and Colin Clubbe (BP)


The importance of island ecosystems

Island ecosystems display many special character-istics (e.g. see Carlquist 1974; Williamson 1981;Whittaker 1998). Many of these result from therelative isolation of islands from other landmasses,and the difficulties that animals and plants experi-ence in dispersing naturally across the sea. Conse-quently, islands provide remarkable opportunitiesto study fundamental ecological concepts andprocesses, including the general rules of biogeogra-phy (MacArthur & Wilson 1967), assembly rulesfor biological communities (e.g. Diamond 1975;Diamond & Gilpin 1982; Gilpin & Diamond 1982)and primary succession (e.g. on Krakatao follow-ing volcanic activity there: Whittaker & Bush1993; Whittaker 1998). Islands can provide alsosituations in which to study the concepts of mini-mum viable populations (e.g. Soulé 1987),metapopulation theory (e.g. Levins 1969; Gotelli1991; Hanski 1996), and the processes ofspeciation and evolution - it is no coincidence thatCharles Darwin and Alfred Russell Wallace bothdeveloped their pioneering theories of naturalselection based on observations made largely ofisland communities (Darwin 1859; Wallace 1902).

Island ecosystems tend also to be rich centres ofbiodiversity. Although they tend to support fewerspecies per unit area than continental landmasses(Whittaker 1998), islands are often home to dispro-portionate numbers of endemic taxa. Some of theseprovide peculiar examples of the evolutionaryresults of living in great isolation, and/or as part ofan ecosystem with relatively few other species.Dispersal ability may be lost, resulting inflightlessness, as seen amongst the birds of NewZealand (e.g. Holdaway 1990), or the endemicbeetle fauna of Tristan da Cunha (Elton 1958;Williamson 1981). Nanism or gigantism mayoccur, producing unusually small- or large-bodiedspecies, respectively. The islands of the Caribbeansupport the world’s smallest species of bird, lizardand snake, but they previously also supported gianttortoises (Case et al. 1992), similar to those foundon the Galapagos and Aldabra. Spectacular adap-tive radiations may occur on islands, resulting inunique suites of closely related but differentiallyadapted species. Hawaii provides a number ofwell-cited examples. Here, a single colonist speciesappears to have given rise to three genera and 54species of tree crickets (Oecanthinae), representingnearly half of the world’s known species (Otte1989), and drosophilid fruit flies have shown an

even greater degree of adaptive radiation, with oneor two founder species giving rise to 700-1000separate species, again accounting for nearly halfof the known world fauna (Whittaker 1998).

The island biodiversity crisis

For all of the reasons outlined above, island eco-systems are of enormous conservation value.However, island biodiversity is particularly threat-ened by the damaging effects of human activities.Available data suggest that a disproportionatenumber of post-1600 extinctions have involved theloss of island species (Groombridge 1992).Amongst well-researched taxa (mammals, birdsand land snails), around 80% of extinctions in thisperiod may have been of island species. There issub-fossil evidence that human impacts also causedsignificant extinction of vertebrate island speciesprior to 1600 (Whittaker 1998). Globally, Case etal. (1992) conclude that human activities haveraised reptilian extinction rates by an order ofmagnitude on small islands, and Steadman (1997)estimates that island bird extinction rates increasedby some two orders of magnitude as a consequenceof human colonisation.

A range of human activities on islands have re-sulted in rapid species extinctions, notably: directremoval of individuals (hunting, timber extraction,etc.); habitat destruction; and introduction of non-native species (including disease agents). On manyislands, introduction of invasive alien species canbe regarded as the most important factor in theelimination of indigenous biodiversity, althoughthe above mechanisms often act in combination(Whittaker 1998). Consequently, there is particularinterest amongst conservationists in the impactsand management of invasive species on oceanicislands (e.g. Vitousek 1988; Veitch & Clout 2002).It is worth noting that these are not new concerns.Charles Elton devoted a chapter of his seminal1958 publication The Ecology of Invasions byAnimals and Plants to remote islands, noting(amongst other things): that New Zealand andHawaii were particularly affected; that the intro-duction of rats and grazing animals were particu-larly damaging to indigenous island biodiversity;that invasive species indirectly (as well as directly)cause extinction of island species; and that someintroduced species fail to establish outside humansettlements, whilst others spread rapidly through arange of habitats.


Island ecosystems and invasive species

Invasive species and their environmental impactshave attracted much concern in recent years. TheConvention on Biological Diversity (CBD) callsfor action against invasive species in its Article 8h,and the IUCN (2000) describes their effects onindigenous biodiversity as “immense, insidious andusually irreversible”. A number of sources considerin detail the environmental impacts of invasivespecies (e.g. Vitousek et al. 1997; Chapin et al.2000; Mack et al. 2000). Globally, invasive speciesare widely-cited as the second greatest threat tobiodiversity after habitat destruction, althoughfigures have been produced which indicate thatthey represent the greatest threat. Hernendez et al.(2002) suggest that invasive species are responsiblefor 39% of all species extinctions since 1600,whilst habitat destruction accounts for 36%.However, as noted above, human-inducedextinctions often occur as a consequence of acombination of factors. As well as environmentaldamage, the huge scale of the economic impacts ofspecies invasions are increasingly recognised (e.g.see Pimentel et al. 2000).

Invasive species impacts on indigenousbiodiversity can be particularly severe on islands.The introduction of species compromises the all-important isolation of island biotas, the verycharacteristic that underpins their special patternsof development. Hernendez et al. (2002) estimatethat 12% of all continental animals (20% of mam-mals, 5% of birds, 15% of reptiles and 3.3% ofamphibians) are threatened by alien invasions.However, the rates of threat increase on islands:31% of animals (11% of mammals, 38% of birds,32% of reptiles and 30% of amphibians). Unfortu-nately, many of the biological characteristics thatmake islands so special, and of such substantialconservation value, also render them particularlyvulnerable to the establishment and impact ofinvasive species (e.g. see D’Antonio & Dudley1995; Cronk & Fuller 1995). Such characteristicsinclude the relative paucity of indigenous species(providing for greater vacant niche space and lesscompetition than would be found on the mainland),the small size of island populations (renderingthem more prone to extinction), and their evolutionin isolation (leading, for example, to loss of defen-sive behaviours and consequent vulnerability tointroduced predators). Other factors that have beencited as increasing the impact of species invasionson islands include the release from natural enemiesexperienced by introduced species (which often

arrive without the predators and competitors thatregulate their numbers in continental populations),and patterns of human exploitation of islands(many New World islands were colonised byEuropeans before the continental mainland, wereimportant trade centres with substantial interna-tional traffic in commodities, and have acquiredvery high density human populations).

The problem of invasive species impacts on islandecosystems is exacerbated by the fact that a singlenon-native species can drive numerous indigenousspecies to extinction, as witnessed by the effects ofintroduction of the Brown Tree Snake Boigairregularis to Guam, or the invasive shrub Miconiacalvescens to Tahiti (Whittaker 1998), for example.Such multiple extinctions can result from directimpacts on similar species (e.g. goats overgrazing arange of native plants), or a combination of directand indirect effects (e.g. the elimination of insectpollinators by an invasive species, leading to plantextinctions, or elimination of plants leading to lossof specialised herbivores).

Coblentz (1998) summarises the impact that anintroduced herbivorous mammal, such as the goator rabbit, can have on an island ecosystem. Theinitial impact is generally severe over-grazing oflocal plants, particularly the more palatable spe-cies. Over-grazing creates patches of bare ground,which may allow enhanced germination of lesspalatable plants (which can come to dominate theplant community), or may remain barren. Smallpopulations of plants may survive in inaccessibleareas, but these can gradually exhaust their seedsupply (as any seed that is dispersed into accessiblesites results in seedlings that are quickly elimi-nated). The death of these relict populations canrepresent the extinction of the species, and with itany other species (such as insects) that haveevolved to depend upon it. The general depletionof the plant community results in loss of habitat fora range of animal species (birds, reptiles, insects),which may also face extinction. The process alsoexposes soils, promoting erosion (and extinction ofthe soil biota), and a once vigorous, diverse ecosys-tem can be replaced by a barren landscape. Om-nivorous species, such as pigs, can have all of theimpacts of a large introduced herbivore, plus thedirect negative effects of feeding on invertebratesand vulnerable stages of vertebrates.

As Coblentz (1998) notes, feral cats and rats onislands are primarily a threat as predators of seabirds and endemic reptiles, and can displace or


extirpate such species very rapidly. It has beensuggested that global seabird numbers have beenreduced by tens of millions due to predation by ratsand cats (Coblentz 1998). Veitch (1998) estimatesthat 30 of 55 seabird species studied on Pacificislands cannot survive in the presence of rats,which also imperil almost all terrestrial insectslarger than 10mm, many reptiles and even certaintree species. Case et al. (1992) conclude thatintroduced predators (dogs, cats, rats, mongooses)have been the main agents of extinction of reptileson small islands, and that large-bodied reptiles witha long history of island isolation have proved mostvulnerable. On the island of Pine Cay (Turks &Caicos Islands), rock iguanas were driven toextinction in just six years by feral cats that origi-nated from pets introduced by resort constructionworkers (Coblentz 1998).

The process of deliberate or accidental introductionof exotic species to islands involves the same(numerous and diverse) mechanisms that lead tomovement of non-native organisms within andbetween continents. Examples of important path-ways (e.g. see Wittenberg & Cock 2001), include:

DeliberatePlants introduced for agriculture/forestryAnimals introduced as livestock or for sportOrnamental plantsOther “aesthetic” introductionsBiological control

Accidental“Contaminants” in traded commodities“Hitch-hikers” in other consignmentsBallast material from shipsEscaped pets, or other captive species

As in continental systems, whilst most invasivespecies are exotic, native species can also becomeinvasive in island ecosystems, usually in responsehuman disturbance of habitats. For example, theBermuda Cedar Juniperus bermudiana, an endemictree, spread across Bermuda after human colonisa-tion, establishing a virtual monoculture in manyareas that had previously supported more diverseplant communities (Wingate 2001). Ironically, theBermuda Cedar was subsequently almost wipedout by an invasive exotic scale insect, and has nowlargely been displaced in the plant community bynon-native Casuarina.

Dealing with invasive species

In tackling invasive species problems, it is gener-ally the case that control measures (includingeradication) are only likely to succeed if they areapplied at an early stage, or on sites that can berelatively well-protected against reinvasion. Conse-quently, prevention rather than control is likely tobe more cost-efficient and effective as a basis forthe management of species invasions. However,islands (by virtue of the strong dispersal barrierthat the surrounding ocean represents) are rela-tively promising sites for attempts at control oreradication of invasive species. Veitch (1998) notesthat rat eradication is eminently feasible on islandsup to 2000ha in area, or larger in some cases, andthat more than 80 islands have been successfullycleared of rodents. Details of many invasivespecies eradication projects on islands are given inVeitch & Clout (2002).

Although prevention and control measures areclearly critical in the management of invasivespecies threats, it is invariably the case that effortsto put management strategies in place also requireconsiderable efforts in gathering and managingrelevant data (so that informed decisions can bemade), and awareness raising across all levels ofsociety (so that the importance of the issue is morewidely appreciated, and political will to address itis generated).

Sharing of experience is vital to dealing withinvasive species threats, to minimise duplication ofeffort, enhance co-operation and increase the speedwith which effective strategies can be developedand implemented. The following sections provide asummary of some of the resources that are avail-able internationally to assist in understanding andmanaging invasive species threats (particularly inisland situations), and the outputs of a workshopsession where conference delegates shared some oftheir experiences with the invasive species prob-lem.

Available resources on invasive species

International initiatives on invasive speciesAs awareness of the importance of invasive speciesissues grows, a number of initiatives are beingdeveloped at local and regional scales. These arevital for the development of legal frameworks andpractical management strategies. However, co-ordination at a global level is also important, tominimise duplicated effort and maximise exchange


of information and ideas.

GISP – The Global Invasive Species Programme(http://jasper.stanford.edu/gisp/)GISP was established in 1997, as a partnershipbetween IUCN (the World Conservation Union),SCOPE (the Scientific Committee on Problems ofthe Environment) and CABI (CAB International).It has become an international partnership networkof governments, institutions and individuals frommany disciplines and backgrounds, workingtowards the GISP mission: To conservebiodiversity and sustain human livelihoods byminimising the spread and impact of invasive alienspecies. GISP is the main vehicle for tacklinginvasive species issues under the CBD (Conventionon Biological Diversity), and works through:awareness raising, establishment of linkages andnetworks, co-ordination of workshops, summaris-ing scientific and technical information. GISP’sactivities focus primarily, but not exclusively, oninvasive species issues in developing countries.

ISSG – Invasive Species Specialist Group(http://www.issg.org/)The ISSG is part of the Species Survival Commis-sion of the IUCN. It is an international group of146 scientific and policy experts on invasivespecies from 41 countries, working towards theISSG mission: To reduce threats to natural ecosys-tems and the native species they contain by in-creasing awareness of invasive alien species, andof ways to prevent, control or eradicate them. ISSGprovides advice on threats from invasive speciesand on control or eradication methods. Its activitiesfocus primarily on invasive species that causebiodiversity loss, with particular attention to thosethat threaten oceanic islands.

Co-operative Initiative on Island Invasive AlienSpecies(http://www.issg.org/islandIAS.html#IslandIAS)Invasive species problems can be particularly acuteon islands (hence the ISSG’s particular focus inthis area). This ISSG initiative exists to facilitateco-operation in key areas of invasive speciesmanagement towards the conservation of islandbiodiversity. The pacific region has provided aparticular focus, but the initiative has a globalremit.

Communication resources relating to invasivespeciesElectronic communication allows rapid exchangeof information and ideas. General electronic

discussion forums, at a local or regional level, suchas Caribbean Biodiversity e-mail group (http://groups.yahoo.com/group/caribbean-biodiversity/)often carry information on invasive species issues.However, the following are (respectively) keyresources globally, in the Caribbean, and for theUK Overseas Territories, in relation to invasivespecies specifically.

Aliens-LThe ISSG’s Aliens-L listserver is the premierinternational electronic forum for discussion andinformation exchange on invasive species. Tosubscribe, send an email without a subject headerto: [email protected] with the mes-sage “subscribe to Aliens-L”. For further informa-tion, see the ISSG website.

Caribbean Invasive Species ThreatsThis electronic forum, moderated by CAB Interna-tional, allows exchange of information and experi-ence in relation to invasive species threats in theCaribbean. To subscribe, send a blank e-mail [email protected] orvisithttp://groups.yahoo.com/groups/carib_ias_threat/

A “Breath of Fresh Air” Discussion Forum(http://www.activeforums.co.uk/Public/)The UKOTCF (Overseas Territories ConservationForum) website hosts this electronic forum fordiscussion of issues relating to the UK OverseasTerritories. Invasive species issues have their owndiscussion group here, for the exchange of viewsand information.

Publications on invasive speciesAliens Newsletter(http://www.issg.org/newsletter.html#Aliens)Produced twice-yearly by the ISSG, this newsletterprovides very readable articles, reviews and otherinformation on invasive species issues (particularlyin a conservation context).

Biological Invasions(http://www.kluweronline.com/issn/1387-3547)An academic journal which provides detailedresearch and review articles on invasive speciesissues.

100 of the World’s Worst Invasive Alien SpeciesA booklet published by ISSG – very useful mate-rial for environmental education. Available as a pdffile (Adobe Acrobat Reader required fordownloading) from the ISSG website at:


http://www.issg.org/booklet.pdf

Turning the Tide: The Eradication of InvasiveSpeciesC.R. Veitch & M.N. Clout (2002). Published byIUCN.This very recently published book provides theproceedings of an international conference on theeradication of island invasives.For details see: http://www.issg.org/Eradicat.html

Invasive alien species: A Toolkit of Best Preven-tion and Management PracticesR. Wittenberg & M.J.W. Cock (2001). Publishedby CAB International on behalf of GISP.This book provides practical advice, illustratedwith numerous case-studies, on prevention andmanagement practices. Available from CABI (http://www.cabi-publishing.org/) or IUCN (http://www.iucn.org/bookstore/).Also available as a pdf file (Adobe Acrobat Readerrequired for downloading) from the GISP websiteat: http://jasper.stanford.edu/gisp/100Toolkitfin.pdfAlso available in interactive web format at: http://www.cabi-bioscience.ch/wwwgisp/gt1goto.htm

A Guide to Designing Legal and InstitutionalFrameworks on Alien Invasive SpeciesC. Shine, N. Williams & L. Gundling (2000).Published by IUCN on behalf of GISP.Aimed at law and policy-makers, this volumeprovides guidance on developing or strengtheninglegal and institutional frameworks for addressingthe invasive species problem, in the context ofexisting international agreements and regionalinstruments. Available from IUCN (http://www.iucn.org/bookstore/).Also available as a pdf file (Adobe Acrobat Readerrequired for downloading) from the CBD websiteat: http://www.biodiv.org/doc/meetings/sbstta/sbstta-06/information/sbstta-06-inf-08-en.pdf

IUCN Guidelines for the Prevention ofBiodiversity Loss Caused by Alien InvasiveSpeciesA set of general guidelines on addressing invasivespecies issues, prepared by the ISSG in 2000.Available at: http://www.iucn.org/themes/ssc/pubs/policy/invasivesEng.htm

Invasive species in the Pacific: a technical reviewand draft regional strategyG. Sherley (ed.) (2000). Published by the SouthPacific Regional Environment Programme, Samoa.This volume collates technical information, and

provides a regional strategy for the management ofinvasive species threats across the islands of theSouth Pacific. Available as a pdf file at: http://www.hear.org/pier/pdf/invasive_species_technical_review_and_strategy.pdf

Other resources relating to invasive speciesGlobal Invasive Species Database (http://www.issg.org/database/welcome/)The ISSG is currently expanding this database,which is likely to become one of the most impor-tant international reference points for invasivespecies information. The database can be searchedby species name, locality, habitat type and otherecological categories.

Other resources relating to islandsAgain, it is worth mentioning resources such as theCaribbean Biodiversity e-mail group (http://groups.yahoo.com/group/caribbean-biodiversity/)which do much to further information exchangeand co-operation between island communities at alocal or regional scale. However, the following hasrecently been established, with a global remit.

Global Islands Network (http://www.globalislands.net/)GIN is a recently established, non-profit organisa-tion with a mission to: Conduct and promoteculturally appropriate, ecologically sound, eco-nomically sustainable and socially equitabledevelopment on islands worldwide. The GINwebsite provides useful links to a range of re-sources and information on islands, at a local,regional and global scale.


Territory Raising awareness Invasive control Invasive preventionAnguilla • We need to define

who/when wedecide a species isinvasive, becausesometimes it isdifficult todetermine whetheror not a problemspecies arrivednaturally.

• Some speciesinvasive in one areaare not necessarilyinvasive elsewherewhich impactswhether or not itbecomes a priority.(Casaurina??)

Ascension • A decision wasmade to controlthe feral donkeys– a letter waswritten to localnewspaper askingfor public input –no one respondeduntil one week’snotice was giventhat the donkey’swere to becastrated – atwhich point a 300person petitionwas presented andthe donkeys wereleft in peace

• Investigate thecommercial valuefor invasives toencourageeradication

• Importance forlegislation, butneeds to be enforced

• Lack of enforcementhas resulted inimport of non-spayed kittens

Australia • There is a move tocelebrate the‘Easter Bilby’ –success story

• Very strict onimports fromMalawi

Bahamas • Working with oneArchitectural firmto develop ofphoto series ofland they areworking on,documentingexisting natives,and the differencein care needed fornative plots versusplots planted withintroduced spp.

• Hutia –endangeredspecies is actuallydestroying theentire ecosystem

• Casaurina’s aproblem, butsomething is nowstarting to kill them

• There is a differentstandard ofrequirements forforeign versus localdevelopment – eg.regulations for localdevelopment don’texist and many lotsonce cleared are leftbarren for manyyears

• Container ships area concern both interms of checks andcontingencyplanning in theevent of anaccident

Dealing with invasive species: sharing knowledge and experience - Workshop output

Rapporteur: Dr Annie Glasspool


Bermuda • We need to identifyALL stakeholders

• We need to engageand get buy-in fromidentifiedstakeholders

• There is a lack ofguidance/information aboutplants being sold inprivate nurseries(invasives are beingsold locally) due toa lack of awarenessamongst nurseryowners

• Awareness wasraised duringhurricane Emilybecause nativespecies survivedmuch better thanthe invasives

• Need to promotethe existing plantvoucher schemewhereby you aregiven x free plantswhen you have aplanningapplication

• Olivewood is inscale with small lotproperties – no leafproblem for homeowners – needs tobe promoted

• Use tourism tohighlight natives –ditch the use ofinvasive species inbrochures etc.

• Learning throughlandscapesprogramme –encouragesawareness throughnative plantings,plus encouragecloser interactionwith environmentand enhance theschool environment

• Need to be sure thatwe can meetdemand withreplacement species

• Currently resourcesare lacking withregards to meetingdemand (money,facilities, skills)

• Dept of Planninginitiated aprogramme so thatthe Cons. Officercan assist locallandowners in awoodlandmanagement planfor their property –but if it expands,supply may becomean issue

• Get tourists to comeand get involved inculling programmes– eg. throughEarthwatch.

• Toad exclusionbarrier establishedon Nonsuch as alocalized control

• Eradication in alocalized area canprovide data whichcan be used topromote furthereradication

• Some species canbe recognised apriori as beinginvasive

• Regulation of pettrade needed butthere are no nativespecies to serve asalternatives; petswhich cannotsurvive in the wildshould therefore beselected.


• We gloss over someinvasives because oftheir cultural identity eg.Whistling frog, grassspecies, Brazil pepper(important for beekeepers)

• So, how would peoplewho currently benefitfrom invasives becompensated?

• Could promote use ofCasaurina for firewood

• Islanders need to acceptthat some pets are notappropriate on anoceanic island

• Cane Toad not flaggedas a problem species inBda but perhaps thisreflects lack ofinformation

• Highlights power ofpublic awareness – toadhas been promoted inthe last few years as aflagship forenvironmental healthbut that has beenmisinterpreted as aconcern for the Canetoad itself

• Shouldn’t ignore thevalue of pets inestablishing respect fornature – but it isresponsible petownership that needs tobe promoted

BritishVirginIslands

• Can insist on planting ofnatives by publicinstitutions

• There are high costsassociated withcontractors workingaround existing nativesso they tend to beremoved


Cayman • Some invasives are apart of the localculture – meaningthat the task in publicawareness would beenormous

• Promote planting ofnative species alongwith promoting theneed to eradicateinvasives

• National Trust iscurrently working onpublic awareness. Butexotics are producedmuch more cheaplythan natives, makingmarketing them hard

• Education is neededso that when peopleare clearing land,natives are left inplace

• Recommendations ofhow much(minimum) nativevegetation should beleft was made in thePlanning Statementbut it has since beenremoved

• Problem with algaebeing produced foraquarium trade

• It is cheaper forplants to be importedthan grown locally

• Could the localGovernment restrictimports or subsidiselocal production –unless this is done,there is currently noincentive for localproduction

• Regulation ofpet trade neededbut no nativespecies asalternatives –but at leastselect pets thatsimply cannotexist in the wildin a particularjurisdiction.

Cyprus • Cannot remove anytree from a propertyunless it is disruptingthe foundations

Falklands • Increase inenvironmentalawareness hasprompted wider useof biological controls,in the absence ofsufficient information

• Reindeer introduced

Isle ofMan

• Need to map data todemonstrate scale ofproblem in order tosecure furthersupport/ justificationof resources

• Misidentification ofspecies can be aproblem – resourcesused when notnecessary


Jersey • Have introducedspecies which havebecome flagshipspp. Eg the Redsquirrel

• Need to considerwhy people adoptsuch species – getto the root cause

• People areconfused by themessage that isbeing sent

• Reinforce thedamage that isbeing done by aspecies

Montserrat • Still trying to getconstructioncompanies to stopclearing areas – toleave natives

NetherlandsAntilles

• Husbandry – eg.Goats

• Ballast water

• Husbandry – eg.Goats

Pitcairn • Culling of invasivesencouraged bypromoting use offelled trees forfirewood – andnatives to replacethem

• More importscoming fromPolynesia now –concerns forprevention ofintroduced speciesassociated withthis

SouthAfrica

• Declared list ofinvasive species

• Benefit to havingdemand greaterthan supply if notexcessive and ifmarketedappropriately

• Fines for havingan invasivespecies onproperty

• Problem withGovernmentpersonnel ‘beingallowed’ to bringin pets

• Don’t just focuson invasives –danger ofcomplacencyregarding thosejust considered tobe introduced – asoceanic islands wecannot afford toignore these


St.Helena

• Success story withEbony

• Value of Opuntia forVitamin C hadn’tbeen taken intoconsideration, norhad impact of itsremoval on hillsides

• Can’t pleaseeveryone – concernat the airport aboutincreasing birds andsafety issues

• A problem withdiseased lemonsegments importedprompted betterregulations onimportations –phytosanitarycertificates etc. –but no one iscurrentlyconsidering woodimports

TurksandCaicos

• A research interestgroup has held aworkshop to raiseawareness of theinvasives problem

• Signage is used toillustrate nativespecies

• Plants sales areheld to encouragepurchase of natives

• Award scheme isbeing implementedto encouragenative plantings

• Visit schools –requests forlabeling of plantsto identify natives

• Enoughinformationcurrently exists todemonstrate thethreat of cats toiguanas – a greatexample of wherean eradicationprogramme isneeded

• Should be conditionsattached to planningregulations – whenand area is cleared, itmust be replacedwith natives

• Space is beingprovided in privatenursery to Trust topropagate natives

• Casaurina’sintroduced (byBermudians) arebecoming a problem– Bermuda hasoffered to subsidisesome replacementplanting with natives

• A bush walking crewconducts plant rescueexercises – but only20 people involved

• A flagship spp is theIguana, but feral catsimpacting iguanas

• There is tradingwith the DominicanRepublic for fruitand vegetables – butplants are broughtin, unregulated (thesame is true withpets – nopapers/quarantineare required)


UK • Need to eliminatethe jargonassociated withinvasives – aproblem wasidentified in tryingto raise awarenessof the issue inethnically diverseschools which led tomisunderstandings

• Talk about specieswhich aredestructive anddamaging (mightinclude endemicstoo). This mightlead to economicincentives eg.Insurance issuessurroundingcasuarinas

• People aredeliberately plantingintroduced speciesin nature reserves to‘increase thebiodiversity’

• Need to come upwith costs of dealingwith invasives tocatch the attentionof the politicians

• If pet imports aresuspended, pettraders refocus onother species whichare also problematic

• Promote prose,storytelling etc. totell the knock-oneffects – eg. TheLighthouse KeepersCat

• Cross-departmentalcontrol of the issuecan mean thatdecisions don’tactually get made –need to have onedepartment incontrol

• Control doesinvolve publicawareness

• Imports can besuspended – currentlyin place for Red-earedSlider terrapin andAmerican Bullfrog

• Need to establish acommittee to developa list of potentiallyinvasive species

• Establishment ofglobal databases suchas GISP will help

US • Promotion of goodpractices important– need to work moreclosely withhorticulturalindustry

• “Barking up thewrong tree” -goodcatch phrase!

• Use of prisoners towork onenvironmentalprojects has beensuccessful


Other • Must stress thepositive element –focus on the factthat a nativespecies will bepromoted – not somuch theeradication of aninvasive species

• Let’s not forgetinorganic invasivespecies – ie trash

• Can’t ignore thefact thatintroduced speciesare attractive topeople –(colourful, cuddlyetc)

• Control often takes along time and ongoingmonitoring andfunding is essential

• How can we make useof our destructiveurges constructively –introduce a tally toencourage competitivenature

• Danger that aninvasive plant mightnot be recognised ifyou are recruitingvolunteers and thewrong plant may beculled

• Marine litter is amajor means ofdispersal of ‘invasivespecies

• FRONTIER – paidcustomers to‘volunteer’ forprojects but marketingis not easy – need avery clear idea ofwhat the programmeinvolves – peopleneed a structuredprogramme – not justpulling up trees

• Need for pilot projects• Most eradication

programmes havebeen done as a lastresort but have lackedthe resources forfollow-up studies

• Spaying and neuteringshould be arequirement but oftennot realistic

• Water hyacinthconsidered forbrickettes for burningin Malawi

• Need to considerissues of diseasewhen consideringreintroducing nativespecies

• Need for exchangeof information aboutgood practicesbetween territories

• Capacity is oftenlacking at point ofimport – socertificates can beissued at point ofexport – but soil forexample presentsproblems

• Use of dedicatedcontainers toparticular locations


References

Carlquist, S. 1974. Island Biology. ColumbiaUniversity Press, New York.

Case, T.J., Bolger, D.T. & Richman, A.D. 1992.Reptilian extinctions: the last ten thousand years.In Conservation Biology: The Theory andPractice of Nature Conservation and Management(ed. P.L. Fielder & S.K. Jain), pp 91-125.Chapman & Hall, New York.

Chapin, F.S., Zavaleta, E.S., Viner, V.T., Naylor, R.L.,Vitousek, P.M., Sala, O., Reynolds, H.L., Hooper,D.U., Mack, M., Diaz, S., Hobbie, S.E. &Lavorel, S. 2000. Consequences of changingbiodiversity. Nature 405: 234-242.

Coblentz, B.E. 1998. Strangers in paradise: invasivemammals on islands. World Conservation 4/97-1/98: 7-8.

Cronk, Q.C.B. & Fuller, J.L. 1995. Plant Invaders.Chapman & Hall, London.

D’Antonio, C.M. & Dudley, T.L. 1995. Biologicalinvasions as agents of change on islands versusmainlands. In Islands: Biological Diversity andEcosystem Function (ed. P.M. Vitousek, L.L.Loope & H. Adsersen), pp. 103-121. EcologicalStudies 115. Springer-Verlag, Berlin.

Darwin, C. 1859. On the Origin of Species by Means ofNatural Selection. J. Murray, London.

Diamond, J. M. 1975. Assembly of speciescommunities. In Ecology and Evolution ofCommunities (ed. M.L. Cody & J.M. Diamond),pp 342-444. Harvard University Press,Cambridge, Massachusetts.

Diamond, J.M. & Gilpin, M.E. 1982. Examination ofthe ‘null’ model of Connor and Simberloff forspecies co-occurrences on islands. Oecologia 52:64-74.

Elton, C.S. 1958. The Ecology of Invasions by Animalsand Plants. Methuen & Co Ltd, London.

Gilpin, M.E. & Diamond, J.M. 1982. Factorscontributing to non-randomness in species co-occurrences on islands. Oecologia 52: 75-84.

Gotelli, N.J. 1991. Metapopulation models: the rescueeffect, the propagule rain, and the core-satellitehypothesis. American Naturalist 138: 768-776.

Groombridge, B. (ed.) 1992. Global Biodiversity:status of the Earth’s living resources. Chapman &

Hall, London. (Compiled by the WorldConservation Monitoring Centre).

Hanski, I. 1996. Metapopulation ecology. InPopulation Dynamics in Ecological Space andTime (ed. O.E. Rhodes, R.K. Chesser & M.H.Smith), pp 13-43. Chicago University Press,Chicago.

Hernandez, G., Lahmann, E.J. & Salicido, R.P-G. 2002.Invasives in Mesoamerica and the Caribbean(results of the regional workshop on InvasiveAlien Species: Meeting the Challenges Posed bytheir Presence in Mesoamerica and theCaribbean, Costa Rica, 11 & 12th June 2001).IUCN, San Jose, Costa Rica. [Availableelectronically at: http://www.iucn.org/places/orma/publica_gnl/especies.pdf]

Holdaway, R.N. 1990. Changes in the diversity of NewZealand forest birds. New Zealand Journal ofZoology 17: 309-321.

IUCN 2000. Guidelines for the prevention ofbiodiversity loss due to biological invasion.IUCN, Gland, Switzerland.

Levins, R. 1969. Some demographic and geneticconsequences of environmental heterogeneity forbiological control. Bulletin of the EntomologicalSociety of America 15: 237-240.

MacArthur, R.H. & Wilson, E.O. 1967. The Theory ofIsland Biogeograpy. Princetown University Press,Princetown.

Mack, R.N., Simberloff, D., Lonsdale, W.M., Evans,H., Clout, M. & Bazzaz, F.A. 2000. Bioticinvasions: cause, epidemiology, globalconsequences and control. EcologicalApplications 10: 689-710.

Otte, D. 1989. Speciation in Hawaiian crickets. InSpeciation and its Consequences (ed. D. Otte &J.A. Endler), pp 482-526. Sinauer, Sunderland,Massachusetts.

Pimentel, D., Lach, L., Zuniga, R. & Morrison, D.2000. Environmental and economic costsassociated with non-indigenous species in theUnited States. Bioscience 5: 53-65.

Soulé, M.E. (ed.) 1987. Viable Populations forConservation. Cambridge University Press,Cambridge.

Steadman, D.W. 1997. Human-caused extinctions ofbirds. In Biodiversity II – Understanding andProtecting Our Biological Resources (ed. M.L.


Reaka-Kudla, W.E. Wilson & W.O. Wilson),pp.139-161. Joseph Henry Press, Washington DC.

Veitch, D. 1998. The invader at our side. WorldConservation 4/97-1/98: 19.

Veitch, C.R. & Clout, M.N. 2002. Turning the Tide:The Eradication of Invasive Species. Proceedingsof the International Conference on Eradication ofIsland Invasives. Occasional Paper of the IUCNSpecies Survival Commission No.27. IUCN,Gland and Cambridge.

Vitousek, P.M. 1988. Diversity and biological invasionsof oceanic islands. In Biodiversity (ed.E.O.Wilson), pp 181-189. National Academy Press,Washington DC.

Vitousek, P.M., D’Antonio, C.M., Loope, L.L.,Rejmanek, M., & Westbrooks, R. 1997.Introduced species: A significant component ofhuman-caused global change. New ZealandJournal of Ecology 21: 1-16.

Wallace, A.R. 1902. Island Life (3rd edn). MacMillan,London.

Whittaker, R.J. 1998. Island Biogeography. OxfordUniversity Press, Oxford.

Whittaker, R.J. & Bush M.B. 1993. Dispersal andestablishment of tropical forest assemblages,Krakatoa, Indonesia. In Primary Succession onLand British Ecological Society SpecialPublication No.12 (eds J. Miles & D.W.H.Walton), pp 147-160. Blackwell ScientificPublications, Oxford.

Williamson, M.H. 1981. Island Populations. OxfordUniversity Press, Oxford.

Wittenberg, R. & Cock, M.J.W. 2001. Invasive AlienSpecies: A Toolkit of Best Prevention andManagement Practices. CABI Publishing,Wallingford (on behalf of the Global InvasiveSpecies Programme).

Wingate, D. 2001. Strategies for successful biodiversityconservation and restoration on small oceanicislands: some examples from Bermuda. InCalpe2000: Linking the Fragments of Paradise -An International Conference on EnvironmentalConservation in Small Territories (ed. M.Pienkowski) pp.16-24. UK Overseas TerritoriesConservation (Available at www.ukotcf.org)


CAB International and biological control of invasive species(posters)

Oliver D. CheesmanCheesman, O.D. 2003. CAB International and biological control of invasivespecies. pp 273-274 in A Sense of Direction: a conference on conservation in UKOverseas Territories and other small island communities (ed. M. Pienkowski). UKOverseas Territories Conservation Forum, www.ukotcf.org

Dr Oliver D. Cheesman, CABI Bioscience UK Centre, Bakeham Lane, Egham,Surrey, TW20 9TY, UK [email protected] www.cabi.org

An introduction to CAB International (CABI) isprovided elsewhere in these Proceedings (p.177).One of CABI’s major interests throughout its longhistory has been the use of biological control – therelease of natural enemies of weeds or pests, tosuppress their populations. For many years, CABIoperated a specific body to co-ordinate work in thisarea (the Commonwealth Institute of BiologicalControl, later the International Institute of Biologi-cal Control). It has published catalogues of biologi-cal control agents used against pests in differentregions of the world, such as Cock (1985) for theCaribbean and Bermuda, and a global catalogue ofweeds and their biological control agents (Julien &Griffiths 1998). CABI continues to research andimplement biological control programmes andregularly publishes reference materials (such asBiocontrol News and Information).

Agricultural weeds and pests provide some of themost obvious early examples of damaging invasivespecies. Biological control has been used to coun-ter them for over 100 years. There is an increasinginterest in the use of biological control againstinvasive species in natural as well as agriculturalecosystems. With increasing sensitivity to thenegative impacts that alien species can have, it mayat first seem counter-intuitive to import deliber-ately more non-native organisms in attempts tocontrol one that has become invasive. Some exam-ples of “biological control gone wrong” are wellknown – the Mongoose in the Caribbean, the CaneToad in Australia. However, these are invariablyamongst the earlier attempts at biological control,involving poorly or unregulated programmes,where the negative impacts could easily have beenpredicted, if only the underlying ecology of pestand natural enemy had been considered. Althoughpoorly regulated biological control programmesremain a potential danger, international standards

have been set for the use of the technique (FAO,1996). Rigorous screening for potential impacts onnon-target organisms is clearly an essential part ofany responsible biological control programme(Thomas & Willis 1998).

Biological control is not always appropriate, nor isit always successful. However, in the right situationit can represent an unrivalled technique for thecontrol of invasive species. Alternative techniques,such as chemical and mechanical control, are oftendamaging to the environment, costly and labourintensive – often needing to be repeated year afteryear. Such techniques may simply be impractical,because of the topography of the affected area, orbecause the invasion is too far advanced. For arelatively small initial investment, biologicalcontrol can provide a self-sustaining solution –using biodiversity to protect biodiversity (Anon.1994).

Successful biological control programmes are oftenforgotten – once a weed or pest problem has beeneliminated, it is easy to forget that it ever existed.Nonetheless, spectacular success stories, like theclearance of invasive Opuntia cactus in Australia inthe 1920s and 30s, are not difficult to find. Al-though economic analyses are scarce, successfulbiological control programmes are estimated tohave saved millions of dollars (Greathead 1995).

The following poster presentations describe someof CAB International’s recent work with biologicalcontrol in the UK Overseas Territories; not againstagricultural pests, but against environmentallydamaging invasive species.

The work to protect the endemic Gumwood Treeon St Helena was one of the first examples ofbiological control being used successfully to save


from extinction a rare species threatened by aninvading alien pest. The success of this programmepaved the way for the restoration of the Gumwood(the Millennium Forest Project) on St Helena – seeCairns-Wicks & Peters (2001).

Although further effort is needed on AscensionIsland, to follow up on initial attempts at biologicalcontrol of Mexican Thorn, the work conductedthere may have contributed to slowing the spreadof this pernicious weed. Biological control mayprovide the only practical solution to the environ-mental threats posed by this vigorously invasivealien plant on the island, and would complementwork undertaken by the RSPB to control cats andrats – see George & White pp.155-160 in theseProceedings.

References

Anon. (1994) Using Biodiversity to ProtectBiodiversity. CAB International, Wallingford.

Cairns-Wicks, R. & Peters, I. (2001) The St HelenaMillennium Gumwood Forest Project. InCalpe2000: Linking the Fragments of Paradise -An International Conference on EnvironmentalConservation in Small Territories (ed. M.Pienkowski) pp. 77-79. UK Overseas TerritoriesConservation Forum, UK (available onwww.ukotcf.org).

Cock, M.J.W. (1985) A Review of Biological Control ofPests in the Commonwealth Caribbean andBermuda up to 1982. Commonwealth AgriculturalBureaux, Slough.

FAO [Food & Agriculture Organisation of the UnitedNations] (1996) Code of Conduct for the Importand Release of Exotic Biological Control Agents(International Standards for PhytosanitaryMeasures, Publication No.3). FAO, Rome.

Greathead, D.J. (1995) Benefits and risks of classicalbiological control. In Biological Control: Benefitsand Risks (eds H.M.T. Hokkanen & J.M. Lynch),pp.53-63. Cambridge University Press,Cambridge.

Julien, M.H. & Griffiths, M.W. (1998) BiologicalControl of Weeds: a world catalogue of agentsand their target weeds (4th edn). CABI Publishing,Wallingford.

Thomas, M.B. & Willis, A.J. (1998) Biocontrol – riskybut necessary? Trends in Ecology and Evolution13: 325-329.

The following two posters should be cited as:

Shaw, R. & Fowler, S. 2003. Biological controlsaves endangered tree from extinction on StHelena. p 275 in A Sense of Direction: a confer-ence on conservation in UK Overseas Territoriesand other small island communities (ed. M.Pienkowski). UK Overseas Territories Conserva-tion Forum, www.ukotcf.org

Djeddour, D., Cheesman, O.D. & Fowler, S.2003. Biological control of Mexican thornProsopis juliflora on Ascension Island. p 276 inA Sense of Direction: a conference on conserva-tion in UK Overseas Territories and other smallisland communities (ed. M. Pienkowski). UKOverseas Territories Conservation Forum,www.ukotcf.org

A Sense of Direction: a conference on conservation in UK Overseas Territories and other small island com

munities, page 275

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Invasive non-native species cause the greatest lossof biodiversity on oceanic islands. The Americanmink Mustela vison is a non-native small carnivorewhich has become established throughout the UKfollowing escapes from fur farms since the 1920s.Farmed mink escaped in the Western Isles (Scot-land) and a feral population is now established on75% of the 2,800 km2 archipelago.

Mink threaten internationally important ground-nesting bird populations (mainly terns) by preda-tion of eggs and chicks. A five-year eradicationscheme is attempting to reduce the impact of minkand assess the feasibility of a pan-archipelagoeradication scheme. The project is funded by theEU LIFE-Nature Fund and a consortium of localbodies led by Scottish Natural Heritage, with thework being carried out by staff from CentralScience Laboratory.

The main aims of the scheme are to eradicate minkfrom a 750km2 trial area of the Western Isles, tocollect data for modelling full eradication, and alsoto remove feral ferrets Mustela furo, another aliensmall carnivore. The main method employed islive-capture cage trapping using 2,500 traps over afive-year trapping campaign. Dogs are used tolocate den sites.

The project has just completed its first 16 monthsof trapping and has achieved over 62,000 trap-nights with 230 mink and 139 feral ferrets caughtto date. Mink population densities are substan-tially lower than previously thought. Most of themink are confined to the coast with the highestdensities on small offshore islands, many close toseabird colonies.

Trapping at den sites has proved highly successfulwhen mink are breeding (a period during which

normal line-trapping is unsuccessful). Locatingmink dens using dogs has also proved very effec-tive. The use of scent-gland-based lures hasimproved efficiency, doubling the capture rate.Traps on floating platforms and the use of mirrorsare also being investigated.

Tern colonies have been counted and breedingsuccess estimated to compare with future trends.As mink numbers decline, rat Rattus norvegicuscaptures have increased, suggesting possible meso-predator release. Modelling indicates that 80-85%of the mink population must be removed perannum to cause extinction in five years.

Mink Mustela vison eradication in the Western Isles, Scot-land, UK (poster)Niall Moore and Sugoto Roy, Central Science Laboratory (Defra)

Moore, N. & Roy, S. 2003. Mink Mustela vison eradication in the Western Isles,Scotland, UK. p 277 in A Sense of Direction: a conference on conservation in UKOverseas Territories and other small island communities (ed. M. Pienkowski). UKOverseas Territories Conservation Forum, www.ukotcf.org

Niall Moore and Sugoto Roy, Central Science Laboratory (Defra), Sand Hutton,York YO41 1LZ, UK [email protected]


The small Indian mongoose Herpestes javanicuswas introduced to several tropical islands to controlrats in the late nineteenth and early twentiethcenturies. Seventy five percent of these islands fallwithin biodiversity hotspots. Its introduction hascoincided with the extinction or population demiseof several rare and endemic birds and reptiles.

Nineteen mongooses were introduced to Mauritiusin 1902, and a century later the species is nowwidespread. The pink pigeon Columba mayeri is aspecies endemic to Mauritius whose wild popula-tion has increased from nine adults in 1990 to over400 today through long-term intensive manage-ment, of which invasive predator managementforms an integral component. Mainlandpopulations of pigeons are currently managed atonly four sites. These populations stem from aremnant population from which the species hasbeen bred and re-introduced. Pigeons are vulner-able to ground predators such as mongooses, whichare controlled using box traps laid out in gridsystems. Although successful, the technique islabour intensive and needs to become more effi-cient to be sustainable in the long-term.

Mongoose ecology was studied to optimise man-agement by targeting the right habitats and spacingtraps optimally. Mongooses were trapped, somewere radio-tracked, while culled specimens pro-vided data used for population modelling.

Mongooses used riparian, rocky and woodlandhabitats preferentially within their home ranges.This was partially corroborated by a study whichfound that traps in forest thickets were most suc-

cessful. Indirect census data also show that densitywas higher in degraded woodlands and riparianhabitats. The mean home range size (MCP) was0.77/km2, and ranged from 0.25-1.1/km2. Densityestimates ranged from 25.6 - 52.4 animals/km2

(mean 37.3). Home ranges overlap considerably,suggesting that the species is not territorial.

The diet was broad: birds occurred in 6% ofmongoose guts (n = 458), predation on pigeonswas low (n = 5). However, modelling has shownthat low level predation can affect long-termviability of pigeon populations. Mongoose controlreduced pigeon mortality rates in the site with thelongest history of management.

Control regimes could be improved as follows:

• Trap siting: Efforts should be biased towardspreferred habitats, i.e. rocky areas, forestthickets and riparian habitats.

• Trap spacing: Trap spacing should correspondwith home range sizes of mongooses (thesmallest was 0.25 km2). Greater trap densi-ties should improve capture rates.

• Diet: Rats are frequently eaten, so controllingmongooses alone may cause future ratproblems through meso-predator release.Carrion is consumed frequently, so poison-ing is a potential alternative mongoosecontrol method.

Mongoose management to protect endangered pink pigeonsin Mauritius (poster)

Sugoto Roy, Central Science Laboratory (Defra), Carl Jones, Mauritian Wildlife Foun-dation and Stephen Harris, University of Bristol

Roy, S., Jones, C. & Harris, S. 2003. Mongoose management to protect endan-gered pink pigeons in Mauritius. p 278 in A Sense of Direction: a conference onconservation in UK Overseas Territories and other small island communities (ed.M. Pienkowski). UK Overseas Territories Conservation Forum, www.ukotcf.org

Sugoto Roy, Conservation Management Team, Central Science Laboratory (Defra),Sand Hutton, York, UK, YO41 1LZ [email protected] Jones, Mauritian Wildlife Foundation, Black River, Mauritius, Indian OceanStephen Harris, School of Biological Sciences, University of Bristol, BS8 1UG

topic 6: dealing with invasive species: sharing knowledge and experience

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