Loses of biodiversity on islands

1
Loses of biodiversity on islands
2
Island biodiversity

• Islands have a very high level of endemism,
  contributing disproportionably to their size to
  biodiversity
• Many classic examples of adaptive radiation and
  lineage diversification (Hawaiian orchids,
  Drosophila, honeycreepers, land snails) may be
  found among the world's islands.
• For the same reason that these species are
  endemic, they are very vulnerable to extinctions.

3
Islands as global hotspots of biodiversity

• Out of 25 global hotspots of biodiversity 8 are
  on islands Caribbean 3, Madagascar 9, Sundaland
  (Malay.Indon.)16, Wallacea 17, Philippines 18,
  New Caledonia 23, New Zealand 24,
  Polynesia-Microneasia 25

4
Islands as global hotspots of biodiversity

• Brooks et al 2002

5
Natural reduction of biodiversity

• Islands are highly vulnerable to natural
  disturbances like hurricanes.  Spiller et al.
  (1998) assessed responses of spiders and lizards
  to disturbance caused by hurricane Lili on the
  Bahama Islands. 
• larger bodied animals (ie. lizards) were less
  vulnerable to being killed during the hurricane
  than spiders, though the small-bodied
  spider populations responded more quickly after
  the hurricane had passed.  
• extinction (or more properly extirpation) from
  islands was related to population size only when
  disturbance was moderate, but not when it
  was intense. 
• After catastrophic disturbance, recovery rates of
  different species were related to their dispersal
  abilities.  Lizards, the least capable
  dispersers, were absent from many suitable
  islands, likely a long-lasting effects of
  catastrophes.  

6
Impact of Hurricane Lilly on Islands in the
Bahamas

• Hurricane Lili hit these islands with a 5m storm
  surge and 90knot winds (Spiller 1998)

7
Natural reduction of biodiversity

• The time scale and effect of disturbances can
  vary greatly (Whittaker 1998)

8
Natural reduction of biodiversity

• Fossil record found 0-3 vertebrate population
  losses for 4000-8000 years prior to humans on the
  Galapagos Islands
• Bone finds in a cave on Tonga reveal little
  prehuman species turnover
• Despite the fact that islands are subject to
  natural disasters like drought, fire and
  cyclones, to date the fossil record has revealed
  no major loss of species from natural causes
  (Steadmann 1995)

9
Natural dispersal does still occur

• Biodiversity on islands is the product of
  immigration, extinction, and in situ speciation
  (in some cases).
• After good dispersers colonize, the rate of
  new, natural species additions may be very low.
  Nevertheless, it does occur. 
• The green iguana lizard Iguana iguana colonized
  the island of Anguilla following a series of
  hurricanes in the Lesser Antilles in 1995.  The
  storm tracks were east-northwest. 
• The iguanas are believed to have originated on
  the island of Guadeloupe, 300 km away Censky et
  al. (1998).  This lizard was previously unknown
  on Anguilla. 

10

• After the storms, a large mat of logs
  and uprooted
• trees washed ashore on Anguilla. Based on local
• observations, it is believed that at least 3
  male and 5
• female lizards were found on and around the mat
  on
• the beach on Anguilla.  One female was in a
• reproductive condition, making it possible that
  this
• colony of immigrants could establish on the
  island.

11
Prehistoric spread of humans

• The earliest islands colonized by sea-faring
  peoples were Australia, New Guinea, New Ireland,
  Sulawesi (Indonesia), and the Solomon Islands
  (earliest islands colonized are listed first). 
  Each of these islands were colonized at least
  28,000 years ago.  Each of these islands lie in,
  or west of, the Melanesian Island chain.  
• Further north and east, the Micronesian Islands
  (Caroline Islands, Marshall Islands, Gilbert
  Islands and Mariana Islands) were colonized about
  4000 years ago.  
• Further east and south, Fiji and New Caledonia
  (both in Melanesia) and Somoa and Tonga (both
  part of Polynesia) were colonized between 3500
  and 3000 years ago.  Further east in the
  Polynesian chain, the Marquesas Islands, Cook
  Islands, Hawaiian Islands, Society (Tahiti)
  Islands and Easter Island were colonized
  in 1500-2000, 1600, 1400, 1200, and 1000-1300
  years ago, respectively.  New Zealand, far south
  of these island groups, was among the last island
  groups colonized (800 years ago) owing to its
  extreme isolation.

12
Prehistoric spread of humans in Polynesia

• Due to a low level of resolution among the human
  populations, Pacific rat mtDNA was used to
  reconstruct human dispersal (Matisoo-Smith et al
  1998). Australia, New Guinea, New Ireland,
  Indonesia, and Solomon Islands at least 28,000
  years ago Micronesian Islands (Caroline Islands,
  Marshall Islands, Gilbert Islands and Mariana
  Islands) were colonized about 4000 years ago

Fiji, New Caledonia, Samoa and Tonga 3500 and
3000. Marquesas Islands 1500-2000, Cook Islands
1600, Hawaiian Islands 1400, Society (Tahiti)
Islands 1200 and Easter Island 1000-1300 New
Zealand, was among the last island groups
colonized (800 years ago)
13
Island extinction
The causes of bird extinctions on islands are due
to human and non-native mammal (rats, dogs and
pigs) predation. Removal or alteration of forests
through cutting, burning and introduction of
non-native plants Soil erosion through
deforestation has eliminated nesting sites for
burrowing seabirds The rate of extinction after
human arrival varied greatly from only 100 years
in many cases (iguanas and birds) (Steadman 2002)
to several thousand years, depending on island
size, habitat diversity, island ruggedness and
human population levels and continuity. Modern
extinctions caused by similar processes than
historic, only the tools have changed (Steadman
1995)
14
Prehistoric extinctions

• Example of Easter Islands bird species (Steadman
  1995)
• On one island in the Marquesas the number of
  nesting seabirds went from 22 to 4.
• On one island on the Society Islands nesting
  birds went from 15 to 4
• Galapagos Islands were only settled by Europeans.
  Excellent fossil records show 0-3 vertebrate
  population losses for 4000-8000 years prior to
  humans, but 21-24 after human arrival

15
Prehistoric extinctions

•  Human colonization of Pacific Islands resulted
  in large numbers of bird extinctions, numbering
  2000 species (mainly flightless rails), or 20
  of global bird diversity.
• Particularly hard hit with extinction or
  extirpation were rails, pigeons, doves, parrots
  and passerines.  Seabirds (mainly shearwaters and
  petrels) have suffered more from extirpation than
  extinction.  Processes responsible for
  extinctions caused by prehistoric peoples
  apparently are similar to those today.
• It is estimated that 90 of extinct bird species
  were inhabitants of islands
• More Polynesian bird species are extinct today
  from human causes than are alive today, and many
  of the survivors have greatly reduced ranges

16
Bird extinctions

• Decline in bird species on a Tonga Island
  depending on foraging height and food type
• Frugivores declined very sharply with a negative
  effect on tree pollination
• Ground feeders (7-0) became extinct caused by
  human and non-native mammal predation Steadman
  1995)

17
Endemic Island Biota Extinction or Endangerments

• More than 10 of Hawaii's tremendously diverse
  plant species  are extinct, and another 40 are
  endangered
• Most of the 331 described species of endemic
  Amastridae (family) snails of  Hawaii are
  extinct, and most of the survivors are
  tree-dwelling species
• The land snail fauna of the Hawaiian islands once
  numbered more  than 750 species (gt99 of which
  were endemic to the islands), though  most are
  now either extinct or endangered. 
• The primary cause of species decline are
  introduction of nonindigenous species (e.g.
  carnivorous snails), and, to a lesser extent,
  destruction or modification of habitat (Cowie
  1998).  

18

• Argentine ants (Iridomyrmex humilis) was
  introduced to
• Maui (Hawai'i) 25 years  ago and presently
  restricts the
• distributions of many gastropods and
  arthropods.
• Some of those arthropods are major pollinators
  of
• endemic plant species, predators,  and
  flightless taxa
• (wolf spiders and Collembolans)(Cole et al.
  1992).
• The little red fire ant (Wasmannia auropunctata)
  was
• first introduced to Indefatigable (Galapagos
  Islands)
• early this century it has since spread to 4
  other islands
• in the archipelago. 
• At least 17 of the 28 ant taxa on the Galapagos
  have
• limited distributions or abundances resulting
  from
• aggressive encounters from the little red fire
  ant.  It
• also eliminated 1 scorpion and 2 spider species
  (Lubin
• 1984).

19
Reasons for the high loss of biodiversity on
islands

• In a meta analysis of a number of factors
  describing islands (latitude, area, elevation,
  isolation, colonization), and comparing them with
  the number of bird species extinct (Blackburn
  Gaston 2005)
• The proportion of bird species extinct was best
  predicted by the isolation of an island and time
  since colonisation, meaning the more isolated and
  the earlier an island was colonized the more bird
  species are extinct
• Hence the less new migrants arrive in an
  ecosystem the less its prepared to deal with them
  particularly if they arrive at high rates
• There is also evidence that human population
  densities were higher on more isolated islands
• The species most likely to become extinct were
  large bodied, flightless, ground-dwelling or
  ground-nesting

20
Causes of Island-based Species Extinctions

• Direct habitat destruction
• Introduced Species
• Overharvesting
• Depletion of food resources

21
Direct habitat destruction

• Direct habitat destruction associated with
  cutting or burning of forests for agriculture,
  construction, and wood extraction.  All
  Polynesian islands were largely or completely
  forested prior to man's arrival many of these
  islands have only small remnants, if any, left of
  this original vegetation. 
• On Easter Island, loss of forest
  cover corresponded not only with massive species
  losses, but also in human misery.  It is believed
  that the people on this island lost their
  primary transportation mode (boats), and then
  their food supply (marine mammals) following loss
  of forest cover. 
• Archaeological records indicate a switch in diet
  from marine foods to rats prior to the
  civilization's demise.  Soil erosion associated
  with deforestation has also resulted in loss of
  nesting sites for some seabirds.

22
Introduced Species

• Animals such as feral goats, pigs, cats, dogs
  and especially rats (European species Rattus
  rattus, Rattus norvegicus Pacific species Rattus
  exulans) caused major damage to native
  vegetation, or competed with or preyed on native
  taxa. 
• Some introduced plants (Miconia in Tahiti
  Psidium in Tubuai, Leucaena in Marquesas, Myrica
  in Hawaii) crowd out native taxa and form
  monospecific stands.

23
Overharvesting

• Many taxa had limited distributions (endemics)
  and thus were vulnerable not only to extirpation
  but also to extinction if exploited heavily. 
• Some flightless birds were almost certainly
  driven extinct because they evolved in
  the absence of mammalian predators and
  competitors and were unwary (naive) of human
  presence and were easily captured. 
• It has been speculated that easy access to these
  often abundant food sources was an important
  factor permitting long distance sea voyages by
  Polynesians and Europeans.

24
Depletion of food resources

• In some cases, extinctions were precipitated by
  loss of food resources associated with
  destruction of habitat or introduced species. 
• For example, the New Zealand eagle Harpagornis
  moorei was likely dependent on moas and other
  large extinct birds.
• Rats (R. exulans) may have caused invertebrate
  declines which reduced food supplies for the
  extinct birds Aptornis  and Megaegotheles.

25
The island of Singapore

• On the island of Singapore, habitat loss over the
  past 183 years exceeded 95! Corresponding with
  this decline was a massive documented or inferred
  loss of biodiversity. 
• Losses were highest for forest specialists
  (34-87 of taxa extinct) in taxa like
  butterflies, birds, fish and mammals. 
• Loss rates were lower (5-80) for vascular
  plants, decapods, amphibians and reptiles. 
• More than 50 of Singapores residual native
  biodiversity is sheltered in reserves that
  account for only 0.25 of the island. 
• Extrapolation of these patterns using
  species-area relationships, reveal that 13-42 of
  regional populations will be lost over the coming
  century, and at least half of these will be
  losses of entire species (Brook et al. 2003)

26
The island of Singapore
27
Plant species in Tonga

• On the Island of Vavao human arrived 2600 B.P.
  identified by charcoal in the sediment core
  indicating burning of the hardwood forest
• Increased soil erosion as documented by clay
  particles in sediments
• The number of frugivorous and nectarivous bird
  species was reduced from 19 to 6 species after
  human arrival
• Among the extinct species are the two largest
  pigeon species on Tonga
• Several large rainforest tree species with large
  seeds have lost their means of seed dispersal
  (Fall 2005)
• Several tree species are not present anymore

28
Lizards and shrubs

• On the Island of Menorca a frugivorous lizard
  became extinct after the introduction
  carnivourous mammals (Traveset Riera 2005)
• The lizard consumed large amounts of the shrubs
  fruits and disperse them through their scat. They
  were found to be the sole disperser of seeds of a
  perennial shrub
• On the islands without the lizard the shrub only
  recruits underneath the parent plant
• This is the most likely reason why this plant is
  endangered

29
The brown tree snake (Boiga irregularis)

• Its native in Australia and was introduced
  accidentally onto Guam in the 1950s
• Overall responsible for the extinction of 3 out
  of 4 pelagic birds 9 out of 13 forest birds 3-5
  out 12 reptile species on the Island of Guam.
• This snake caused the extirpation or serious
  reduction of most of the island's 25 resident
  bird species on the main island of Guam.
• Twelve species were likely extirpated as breeding
  residents on the main island, 8 others
  experienced declines of greater than or equal to
  90 throughout the island or at least in the
  north, and 2 were kept at reduced population
  levels during all or much of the study.

30

• Declines of greater than or equal to 90
  occurred rapidly,
• averaging just 8.9 years along three roadside
  survey routes
• combined and 1.6 years at a 100-ha forested
  study site (Wiles et
• al 2003, Rodda 1998).

• (Wiles et al 2003)

31
New Zealand

• The islands were colonized by humans only
  1000-800 years ago because of their isolation. 
  Endemism is high on oceanic islands in this
  group, though diversity is lower than on the
  larger (continental) islands. 
• The archipelago has extraordinary biodiversity
  including 75 of the world's penguins, 54 of
  seabirds (albatross, petrels, and shearwater),
  80 of baleen whales, 50 of beaked whales and
  36 of dolphins.  The islands also support many
  endemic species, including 35 of macroalgae, 55
  of sponges, 45 of bryozoans, 20 of fish, and
  30 of seabirds. 
• This tremendous diversity has resulted from the
  islands' range of climates (subtropical
  to subantarctic), isolation (oceanic to
  continental), latitudinal diversity, and age. 
• Over the past 200 years, 48 of the native
  avifauna has been rendered extinct owing to
  habitat destruction and introduced mammals (see
  below). Other factors responsible for destruction
  of endemic avifauna (particularly flightless
  birds) include overhunting and collections. 

32
New Zealand

• Reasons why New Zealand's biodiversity still is
  high
• human colonization was so recent, large
• tracts of evergreen forest remain
• introductions were limited to the mainland
• areas, thus preserving biodiversity on
• smaller, adjacent islands
• public demand for preserving species and
• restoring ecosystems.

33
New Zealand

• 120 eradication programs have created 'new'
  habitats for the 500 or more species threatened
  on the archipelago.  New Zealanders are
  also trying to rid the archipelago of ornamental
  plants introduced by British colonists
  'acclimatization societies'  
• Reforestation programs aimed at restoring native
  vegetation and habitats have proven successful,
  and in some cases have helped endangered animals
  recover. 
• For example, the black robin (Petroica traversi)
  numbered only 9 individuals in 1975 the 7 (2
  breeding pairs) birds were captured in 1976-1977
  and moved from its degraded habitat on Little
  Mangere Island to Mangere and later to South East
  Islands.  These larger islands had much better
  (and improving) forest conditions.  The species
  was on the brink of extinction (10-15
  individuals) for 8 more years before eggs
  were cross-fostered with Chatham Island Tits,
  which increased production of black robin
  fledglings. In 1992 the species totalled 120
  birds.

34

• Helicopter-dispersed rodenticide eliminated rats
  from Red Mercury Island after the 20 resident
  tuataras were removed.  These individuals have
  been in a captive-breeding program, and will soon
  be re-established on the rat-free island. Two
  rare skinks will also be reintroduced to
  the island. Programs of ecological restoration
  and habitat rehabilitation are ongoing on many of
  the nation's islands and are critical to survival
  of many endemic plants and animals.
• Captive breeding programs are presently helping
  two endangered flightless birds the nocturnal
  parrot Kakapo (Strigops habroptilus), of which 50
  individuals remain, and the gallinule Takahe
  (Porphyrio mantelli), of which 150 individuals
  remain (Clout and Craig 1994).  These
  species were both thought extinct before small
  populations were found. 

35
Chatham Island black robin
tuatara
kakapo
takahe
36
Kakapo example (Elliot 2001)
The Kakapo (Strigops habrotilus) is a large
parrot (1.5-4kg) endemic to New Zealand and on of
the worlds rarest birds (62 individuals)

• Its a flightless, nocturnal, herbivorous, lek
  breeder that breeds only every 2-5 years and
  leaves the eggs unattended for long times
• While protected from visual predators, predators
  hunting by smell can are a threat. Rats and dogs
  were introduced by the Polynesians and Europeans
  introduced rats, cats, mustelids (ferrets and
  weasels) all prey on Kakapos
• Additionally the native forest is reduced in
  large areas, but the main problem is predation
• By the 1970 only two populations on Stewart
  Island and in the Northern Fjordland remained

37

• Due to high mortality of adult parrots caused by
  cats, all animals were translocated to three
  relatively predator free islands in the
  1980s-1990s
• Adult survival was between 98-99, but only three
  chicks were reared until 1995, leading to a much
  more intensive and intrusive management of the
  species
• As the Kakapo nesting seem to coincide with large
  crops of fruits and seeds every 3-4 years,
  supplementary feeding was used to increase the
  breeding frequency. Feeding also reduced the
  amount of time the female was away from the eggs.
• A total of 15 chicks have fledged since 1995

38

• In order to prevent any further loss of eggs or
  chicks to predators all nests were continuously
  monitored and traps and deterrents were used to
  remove predators
• Between 1981-1994 43 of the nestlings were eaten
  by rats. Since intensified protection the overall
  chick mortality has dropped from 75 to 29
• Potentially infertile males are removed to other
  islands
• The last remaining male of a different island
  population was moved to an island with several
  females
• Eggs or chicks which were considered failing were
  removed from the nests and hand reared and later
  released

39
Vertebrate invaders in New Zealand
40
Invader control

• Removal of invasive species is an expensive and
  labour intensive approach
• Low level control efforts may help protect select
  native species, current eradication
  methods,limited conservation funds, and the
  potential negative non-target impacts of
  sustained control efforts all favour an intense
  eradication effort, rather than a sustained
  control program

• Eradication of feral pigs from Santiago Island in
  the Galapagos Archipelago, Ecuador, which is the
  largest insular pig removal to date
• Using a combination of ground hunting and
  poisoning, over 18,000 pigs were removed during
  this 30-year eradication campaign

41
Feral Goats

• Goats were introduced to many islands by sailors
  in order to establish food sources (Saint Helena,
  Juan Ferndandez, Hawaii)
• Island biotas mostly evolved largely without
  large mammalian herbivours, and therefore where
  ill adapted
• Introduced goats, changed the composition of
  plant communities, caused extinctions and
  accelerated soil erosion
• Goats are identified as the primary threat to 26
  of threatened insular plant species (IUCN)
• They can be the sole reason or a contributing
  factor for island extinctions
• Fauna recovery after goat removal is often
  dramatic even with long-standing goat populations
  (for example Pinta and Santiago Islands
  Galapagos) (Campell Donlan 2005)
• The use of GIS aided hunting techniques and Judas
  Goats greatly increased the efficency and reduced
  the costs of these programs

42

• Campbell Donlan 2005

43

• Campbell Donlan 2005

44
Conservation strategies

• New Zealand only has three native mammals, bats,
  as it has been separated from Gondwana for at
  least 75million years (Atkinson 2001)
• Native animals and plants are not adapted to the
  pressure from mammalian predators and herbivores
  respectively

11 species of Moas and the large Haasts eagle
became extinct Original restoration efforts on
the smaller islands. It was immediately realized
that mammal eradication is a key part 36 near
shore islands and 16 offshore islands have been
cleared of mammals
There are also 18 mainland islands of a total
area of 28,360ha created were invasive animals
and plants are controlled in order protect natives
45

• Atkinson 2001

46
Summary

• Large losses of biodiversity have already
  occurred on islands
• Many species are endangered and threatened with
  extinction
• Key point for conservation is the removal of
  invasive species
• Better and more efficient tools are available for
  the removal of mammalian predators and herbivores
• There are several success stories of conservation
  and restoration of island habitats

47
References

• Biological Conservation 99 (1) issue on
  Introduced pest species and biodiversity
  conservation in New Zealand several good articles
• Whitaker RJ 1998. Island Biogeography, Ecology,
  Evolution, and Conservation, Oxford University
  Press. BOOK
• Censky, E.J. et al. 1998. Over-water dispersal of
  lizards due to hurricanes.  Nature 395556. 
• Brooks TM, Mittermeier RA, Mittermeier CG, et al.
  Habitat loss and extinction in the hotspots of
  biodiversity CONSERVATION BIOLOGY 16 (4)
  909-923 2002
• Spiller DA, Losos JB, Schoener TW Impact of a
  catastrophic hurricane on island
  populations SCIENCE 281 (5377) 695-697 1998
• Steadman DW, Pregill GK, Burley DV  PROCEEDINGS
  OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED
  STATES OF AMERICA 99 (6) 3673-3677 2002
• Elliott GP, Merton DV, Jansen PW Intensive
  management of a critically endangered species
  the kakapo BIOLOGICAL CONSERVATION 99 (1)
  121-133 2001
• STEADMAN DW PREHISTORIC EXTINCTIONS OF PACIFIC
  ISLAND BIRDS - BIODIVERSITY MEETS ZOOARCHAEOLOGY 
  SCIENCE 267 (5201) 1123-1131 1995
• Saunders A, Norton DA Ecological restoration at
  Mainland Islands in New Zealand  BIOLOGICAL
  CONSERVATION 99 (1) 109-119 2001
• Campbell K, Donlan CJ Feral goat eradications on
  islands  CONSERVATION BIOLOGY 19 (5) 1362-1374
  2005
• Blackburn Gaston 2005 Biological invasions and
  the loss of birds on islands insights into the
  idiosyncrasies of extinction. Sax DF, Stachowicz
  JJ, Gaines SD, (eds) Species invasions insights
  into ecology, evolution, and biogeography BOOK
• Fall PL Vegetation change in the coastal-lowland
  rainforest at Avai'o'vuna Swamp, Vava'u, Kingdom
  of Tonga QUATERNARY RESEARCH 64 (3) 451-459
  2005
• Traveset A, Riera N Disruption of a plant-lizard
  seed dispersal system and its ecological effects
  on a threatened endemic plant in the Balearic
  Islands  CONSERVATION BIOLOGY 19 (2) 421-431
  2005
• Cowie, R.H. 1998. Patterns of introduction of
  non-indigenous non-marine snails   and slugs in
  the Hawaiian Islands. Biodiversity and
  Conservation 7349-368.
• Cole, F.R., A.C. Medeiros, L.L. Loope and W.W.
  Zuehlke. 1992.  Effects of the Argentine ant on
  arthropod fauna of Hawaiian high-elevation
  shrubland. Ecology 131313-1322.

48
Lubin, Y.D. 1984. Changes in the native fauna of
the Galapagos Islands following invasion by the
little red fire ant, Wasmannia auropunctata.
Biological Journal of the Linnean Society
21229-242. Brook BW, Sodhi NS, Ng PKL
Catastrophic extinctions follow deforestation in
Singapore  NATURE 424 (6947) 420-423 JUL 24 2003
Wiles GJ, Bart J, Beck RE, et al.Impacts of the
brown tree snake Patterns of decline and species
persistence in Guam's avifauna CONSERVATION
BIOLOGY 17 (5) 1350-1360 OCT 2003 Atkinson
IAEIntroduced mammals and models for
restoration BIOLOGICAL CONSERVATION 99 (1) 81-96
MAY 2001