AplaneA plane crashes on a remote tropical island. Its marooned passengers soon discover that

their new home is also populated by bizarre creatures—from marauding polar bears to a

mysterious man-eating beast. This is the premise of Lost, currently one of TV’s top-rated

dramas. While the creatures on Lost may be fantastically fictional, the idea that islands

harbor unique and otherworldly creatures is very much rooted in reality. �

“Many of the world’s gaudiest life forms, both plant and animal, occur on

islands,” writes David Quammen in The Song of the Dodo, a book that engagingly

examines island biogeography, the study of species distribution on islands.

Island BiomesPARADISE IN PERIL

“These improbable creatures…givevivid biological definition to the veryword outlandish.”

Perhaps the creators of Lost hadQuammen’s words in mind whenthey plopped polar bears down ontheir uncharted desert isle. If thepresence of arctic animals in the

South Pacific setting seems utterlypreposterous, imagine the Dutchpilot who in 1910 first reported see-ing enormous “prehistoric” lizardsliving on the island of Komodo. Orthe first humans to lay eyes uponthe fearsome-looking “demon-headed” babirusa in the Indonesian

archipelago.Sometimes truth really is

stranger than fiction.

THE BIG AND SMALL OF ITIt’s impossible to discuss islandcreatures without employing theuse of superlatives. From thedragons of Komodo to the devilsof Tasmania, islands boast someof the world’s biggest, smallest,

and most distinctive creatures.“Islands are the world’s great reposi-tories of biodiversity,” says Duane Sil-verstein, executive director of Seacol-ogy (www.seacology.org), a nonprofitorganization devoted to preservingisland habitats and cultures. A dis-proportionately high number ofisland species are also endemic—they’re found nowhere else in theworld. Take Madagascar, where morethan 6,000 of its plants, 100 of itsbirds, and 80 of its mammals arefound nowhere else.

Compared to their mainland rela-tives, island species tend towardeither gigantism or dwarfism. Thelargest lizard, the aforementionedKomodo dragon, which measures up

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� The tiny Malay chevrotain or

“mouse deer” inhabits the islands of

Sumatra, Borneo, and Java.

B Y B R E N D A P O S A D A

Islands conjure up idyllic images of sandy beaches

and swaying palm trees, but they are also home to

some of nature’s most extreme—and most

endangered—life forms.

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to 10 feet long, lives on Komodo andneighboring isles. Giant tortoisesweighing up to 600 pounds reside onthe islands of Aldabra and the Galápa-gos. The fossil record is full of furtherexamples, including dwarf elephantsand pygmy hippopotamuses, whichroamed the Mediterranean and Mada-gascar, respectively. California’s Chan-nel Islands were once home to apygmy mammoth, the ultimate oxy-moron.

The trend toward bigness or small-ness on islands may seem arbitrary,but some patterns have emerged.Island mammals tend towarddwarfism; reptiles, birds, and insectstoward gigantism. Many interrelatedfactors govern why a specific speciesgrows bigger or larger, most impor-tantly food availability, metabolism,

and the presence or absence of preda-tors and competitors. To take onesimplified example, if a small-bodiedspecies has no predators and a plenti-ful food supply, over time it is likelyto grow larger as the advantages ofbigger body size (defense, better fatstorage for lean times and bodywarmth) mean that the largest indi-viduals of each generation are likely toproduce more offspring that survive toreproductive age.

To take a counter example, forlarge mammals, food supply is morelimited. The absence of predatorsleads to an overpopulation of thespecies, straining the available foodsupply. Smaller individuals, who needless food to survive, have a reproduc-tive advantage. The result, over gener-ations, is dwarfism.

Flightlessness is a common evolu-tionary outcome for island birds, anda logical result of the trend towardgigantism. Eventually, larger birds losetheir ability to fly—or flee. When anisland once free of predators is nolonger so, flightless birds have a dis-tinct disadvantage. The doomed dodoof Mauritius was the first recordedspecies to be driven to extinction byhuman activity, around 1692. The ele-phant birds of Madagascar and themoas of New Zealand fared no better,but some extant examples remain:The Galapagos cormorant is largerthan all other cormorants, and theonly one of its kind that can’t fly.

In addition to big birds and minia-ture mammals are the just plain oddinhabitants of island biomes. TakeVisayan warty pigs, found on only two

� The Komodo dragon and Galapagos tortoise provide striking examples of the trend toward gigantism in island species.

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islands in the Philippines. Males of thisspecies grow long, floppy manes inNovember and shed them at the end ofthe breeding season. No other wild pigin the world is known to do this.

ISLAND INSPIRATIONSExactly why islands harbor the weirdand wonderful of the world is a ques-tion that has prompted centuries ofscientific investigation. History’s mostnotable naturalists, Charles Darwinand Alfred Russel Wallace, who con-comitantly hit upon the theory of evo-

lution by natural selection, both foundinspiration in their travels to islands.Wallace made his most profound real-izations in the islands of SoutheastAsia; Darwin in the Galapagos.

Darwin and Wallace were not onlydrawn to islands for their unique crea-tures, but because their limited sizeand isolation render them veritable liv-ing laboratories. They allow patterns ofevolution to be seen more clearly.What Darwin and Wallace realized isthat from a single colonizing species, anumber of different forms arise to fill

available ecological niches, each spe-cially adapted to a particular environ-ment or food source.

This process is now known as adap-tive radiation. The finches of the Gala-pagos Islands, collectively called Dar-win’s finches, provide a classicexample. In the Galapagos, 14 finchspecies arose from a common ancestor.Even more impressive are Hawaii’shoneycreepers. From a single founder,a North American finch, at least 50varieties arose to fill different availableniches throughout the Hawaiian

� Honeycreepers� bills are specialized

based on each species� primary food

source. The �i�iwi mainly feeds on nectar

from lehua blossoms.

� � Male babirusa are known for their bizarre tusks, which, if they�re not worn down or broken in

combat, will eventually grow long enough to pierce the animal�s skull.

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biogeography: The study of the geographic distribution of species.

biome: An ecological community defined by climate and biology.Tropical rain forest, grassland, desert, and wetlands are examples offamiliar biomes.

cay: A low island or coral reef.

colonization: The establishment and successful reproduction of apopulation in a place formerly unoccupied by that species.

continental island: An island that was at one time connected to acontinent. dispersal: The spread of animals, plants, or seeds to a new area.

endangered: A species that is in danger of extinction throughout allor a significant portion of its range.

endemic: Restricted to a specific geographic region.

Island GlossaryIsland Glossaryadaptive radiation: The diversification of a single species intoseveral new species or subspecies that are each specialized to a specificecological niche.

archipelago: A group or chain of oceanic islands.

atoll: A ring-shaped coral reef or string of coral islands.

biodiversity hotspot: Term coined by Dr. Norman Myers in 1988to refer to a region characterized by high levels of both plantendemism and habitat loss.

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exotic: An organism introduced to a region from elsewhere.

extinct: A species that is no longer in existence.

extirpated: A species that has been completely removed from aparticular area, but which still exists in another area. Also known as�locally extinct.�

fauna: The animal life of a particular region.

feral: Formerly domesticated animals that have reverted to a wildstate.

flora: The plant life of a particular region.

insular: Relating to, characteristic of, or situated on an island.

introduced species: An organism that has been brought into anarea it did not previously inhabit, usually as the result of human activity.

Introduced species often compete with and cause problems for nativespecies. Often called exotic, invasive, non-native, or alien species.

land bridge: A connection between two land masses, especiallycontinents, that allows plants and animals to migrate from one to theother.

natural selection: A natural process tending to favor the �survivalof the fittest,� the survival and reproduction of those individuals orgroups best adapted to a particular environment.

niche: All the components of the environment with which anorganism or population of organisms interacts, including its habitat andfood supply.

oceanic island: An island that has never been connected to acontinent. Oceanic islands usually arise as the result of volcanicactivity.

islands. This specialization is most evi-dent in the shapes of the birds’ bills,from the slender, curved bill of nectar-gathering honeycreepers to the thick,stout bill of seed-eating species.

ISLANDS 101imply put, an island is a land masssurrounded by water. Despite theobviousness of this statement,there is ongoing debate overexactly what constitutes an islandand whether larger land masses likeAustralia should be consideredislands. Webster’s dictionarydefines an island as “a tract of landsurrounded by water and smallerthan a continent,” which wouldrule out Australia. Though many of

the same principles apply when dis-cussing Australia’s koalas and kanga-roos as New Zealand’s kiwis and kaka-pos, semantically speaking, Australiabelongs in the realm of the continents.

An island’s biological life has muchto do with how and when it wasformed. Generally speaking, largerislands have more species than smallerones. Old islands have more speciesthan young ones. Continental islandswere once connected to a neighboringcontinent, and were therefore alreadyinhabited by the flora and fauna of themainland at the time they wereformed. The similarity of life forms ona continental island to those on themainland depend on the length of timesince separation. If the separationoccurred fairly recently, the island’sflora and fauna will greatly resemble

that of the continent. Despite its closeproximity to Africa, Madagascar har-bors a wide array of species unlike anyever seen on the continent. Geologistsestimate its separation occurred morethan 160 million years ago.

Oceanic islands, on the other hand,evolve from a geologic process such asvolcanic activity, and have to startfrom scratch. “A continental islandbegins with everything, and everythingto lose,” in Quammen’s words, while“an oceanic island begins with noth-ing, and everything to gain.”

How they gain is a process referredto as colonization. New species arrivemainly by flotation, being carried bywind, or in the case of birds and bats,flying. In 1883, the volcanic island ofKrakatau erupted, killing off all livingthings on the island and creating atsunami that destroyed 295 coastaltowns and villages. But pretty much assoon as the lava cooled, the island—orwhat remained of it—began torebound. Three years after the erup-tion, a visiting botanist recorded 11

different varieties of fern prospering onRakata, the island’s new name (thename was derived by removing thefirst and last letters from Krakatau).Ferns are good colonizers becausetheir spores disperse easily on thewind. Twenty years later, a zoologicalexpedition to Rakata noted the pres-ence of birds, bats, and lizards. Thenumber of species on Rakata is stillincreasing, under the watchful eye ofscientists.

The first creatures to colonize anarea after it has been devastated byvolcanic blast are usually insects,which blow in on the wind and stickto cooling lava like flies to stickypaper. After the insects come birds,which usually arrive accidentally,blown off course during a storm, forexample. Soon thereafter plantsappear, either from buoyant seedsthat make the journey by sea, lighterwind-borne seeds, or seeds carried onthe wings or feet (or in the digestivetracts) of birds. Floating wood or veg-etation acts as a raft for a variety of

� Oceanic islands (left) tend to be more isolated than continental islands,

which are often found just offshore from the mainland.

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living things to make the journey. Oceanic islands tend to be largely

devoid of mammals, which don’t travelas well across open water as birds andreptiles. Even if a mixed-sex pair doesmanage to make a sea crossing, thelikelihood of them establishing a viablepopulation in the new territory isslight. They just aren’t as adaptable asreptiles, plants, and birds.

Continental islands are more likelyto harbor mammals, which, if theyweren’t already present at the time ofseparation, may have swum over fromthe mainland or walked across a long-ago land bridge.

PARADISE LOST?The very features that make islandshotspots of biodiversity also makethem among the earth’s most vulner-able ecosystems. “In the last 400 years,the majority of all plant and animalextinctions on this planet haveoccurred on islands,” says Silverstein,who adds that in the United States,nearly three-quarters of all extinctions

have taken place onHawaii, which composesless than 1 percent of ourcountry’s total land mass.Today, 85 percent ofHawaii’s endemic plantspecies are in danger ofextinction, according tothe World ConservationUnion (IUCN).

All island species are atrisk, but life is muchriskier for island birdsand reptiles, according tothe IUCN’s recentlyreleased Global SpeciesAssessment report. Of allrecorded species extinc-tions since 1500 A.D., thereport states, “In total,62 percent of mammals,88 percent of birds, 54percent of amphibians,86 percent of reptiles,and 68 percent of mol-lusks were island species.”

The greatest threat toisland species is theintroduction of non-

natives such as goats, pigs, cats, andrats. Invaders may directly prey onnatives, outcompete them for food andspace, destroy their habitats, or carrydiseases for which locals have no natu-ral resistance.

The combination of invasives and asmall geographic range can be deadlyfor island species. “On an island,there’s no place to run, no place tohide,” explains Silverstein. “If a birdhabitat is threatened on a major conti-nent, there is very likely to be 50, 100,1,000, or maybe only 3 or 4 otherhabitats for that bird on that samelarge continent. But more often thannot on a small island, there will be justone little area where they live. Andthen a new predatory species is intro-duced, and that’s it.”

Perhaps the most dramatic exampleof this is the brown tree snake onGuam. Prior to the 1940s, Guam washome to only four species of snake; allwere small and relatively harmless. Atsome point during the late 1940s orearly 1950s, the brown tree snake—a

mildly venomous variety that grows upto eight feet long—was accidentallytransported from its native range in theSouth Pacific to Guam, most likely as astowaway on a military cargo ship-ment. With no natural predators andan abundance of small-bodied prey,this nocturnal climber proliferated inits new habitat. By the mid-1980s, thesnakes had virtually emptied Guam’sforests of their native birds and lizards.Twelve bird species, including theMicronesian kingfisher, were com-pletely eliminated. Several others hadtheir numbers drastically reduced.

The brown tree snake has becomepublic enemy #1 on Guam, causing fre-quent power outages, killing domesticpets, and injuring children. They areresponsible for millions of dollars indamage annually. Today, some forestedareas contain an estimated 13,000snakes per square mile, according tothe U.S. Geological Survey. With littlehope of ridding Guam of this perniciouspest, scientists are concentrating theirefforts on keeping the snake fromhitching a ride to other islands, likeHawaii. In the last five years, the USDAhas trapped more than 5,000 snakes atGuam’s international airport!

Whether they are introduced acci-dentally or intentionally, as in the caseof the feral pigs on California’s ChannelIslands (see story on page 12), non-native species can wreak havoc onecosystems.

Other factors contributing to thevulnerability of island species are habi-tat destruction, hunting, disease, thepet trade, and climate change.

Species inhabiting smaller islandsare more vulnerable to extinctionthan those living large. If a populationis small to begin with, the introduc-tion of a new predatory species or theoccurrence of fire, disease, or othernatural event, may kill enough indi-viduals that there is no longer a viablepopulation left to perpetuate thatspecies. Moreover, species on smallerislands may have weaker immune sys-tems, according to a recent study byresearchers at the University ofMichigan. Small species’ lack of immu-nity is a natural result of their being

� Since its accidental arrival in Guam a half century

ago, the brown tree snake has irrevocably altered the

island’s ecology and economy.

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exposed to fewer parasites in thecourse of their secluded existence.When new parasites are accidentallyintroduced to a small island, thenative species are extremely vulnera-ble to infection.

The isolation that once protectedisland biomes has vanished, the victimof international air and boat traffic,commercial fishing fleets, and globalcommunication and economy. Silver-stein reflects, “The poet John Donnesaid, ‘No man is an island.’ If he werealive today, he might say, ‘No island isan island.’ They’re not really islandsany more.”

THE HUMAN ELEMENT

he precarious state of island plantand animals species is mirrored bytheir human residents, accordingto Silverstein, who points out thatisland cultures and languages arealso in dire straits. Rather thanfocusing solely on saving islandwildlife, Seacology looks for solu-tions that address the needs ofpeople as well.

With 109 projects throughoutthe world, Seacology works withisland communities to figure out howto best help them protect their ownenvironments. “We go to the islandvillagers and say, ‘What do you want?Not what we, sitting in an office inthe U.S., say you should want, butwhat do you want in exchange for set-ting aside a forest reserve or a marinereserve for, say, twenty years?’ Andtypically they will say they want aschool or a community center or awater-delivery system.”

Building such a facility in an impov-erished region—where per capitaincome may be less than $100 annu-ally—helps villagers resist pressurefrom developers, logging companies,and commercial fishing fleets that seekto exploit their island’s naturalresources. This in turn helps preservethose resources for generations tocome. “You really can’t have effectiveconservation without taking intoaccount people who live in theimpacted areas,” says Silverstein.

How this equation works comes

home in one of several examplesoffered by Silverstein. The Hainan gib-bon, the most endangered relative ofthe golden-cheeked gibbons housed atthe Los Angeles Zoo, lives on HainanIsland off the coast of China. Thebiggest threat to its survival is defor-estation, as the needs of the burgeon-ing human population for charcoal andlumber are fast depleting China’sforests. Working with a local China-based organization, Seacology reachedan agreement with the four tribal vil-lages on the outskirts of BawanglingReserve, home to all known remainingHainan gibbons (fewer than 20 indi-viduals). In exchange for scholarshipsfor roughly 200 middle schoolers (in aregion where few kids stay in schoolpast sixth grade), the villagers havepromised to stop cutting down thetrees. They are also being trained inalternatives like honey harvesting andherb farming. “So we’re helping tosave arguably the world’s most endan-gered primate, and at the same timeproviding scholarships for every mid-dle school-age child in four villages,”says Silverstein.

The Nature Conservancy (nature.org) and Conservation International(www.conservation.org) are amongdozens of organizations that work topreserve fragile ecosystems, includingsome island regions. Among the NatureConservancy’s projects are theSolomon Islands, the U.S. VirginIslands, the Grenadines, Palau, andCalifornia’s own Santa Cruz Island.Conservation International focuses onsaving biodiversity hotspots, areas thathave already lost at least 70 percent oftheir original vegetation. Many of the34 hotspots they have targeted areisland regions, including Madagascar,Polynesia, and New Zealand.

While the plucky survivors of Lostcontinue their weekly struggle for sur-vival, so too real-life island inhabitantsface an uncertain future. Islandspecies are about 40 times more likelyto go extinct than their continentalcounterparts. Without widespread,collaborative conservation effortsbetween international and local com-munities, the fantastic flora and faunaof islands may soon only be the stuffof television and movies. �

� � Seacology projects include

guarding Vietnam�s Cat Ba langur,

building community centers (like this

one in Papua New Guinea) in exchange

for rain forest preservation, and

installing EcoReef modules to

rehabilitate coral reefs in Indonesia.

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