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Some thoughts on threats
to island biodiversity…
Questions, questions….
• ExtinctionExtinction- a way of
•
•
Extinction as a way of life
life?
HumansHumans- a ‘recent’
recent’
addition to the
extinction process?
IASIAS- the risks of
taking a narrow view?
Evidence for the theory
Diamond (1969)(1969)- turnover in bird
species on Californian Channel
Islands
• 9696-98% of all species
on Earth now extinct
• “struggle for existence”
existence”
Darwin, 1859
• Understanding the
processprocess- lessons from
islands…
islands…
• (MacArthur & Wilson, 1967)
• Simberloff & Wilson (1969)(1969)-
Equilibrium in insect species
richness on near and far
islands in Florida keys
Adding humans to the mix
• Humans as invasive
species? Adapted from Martin, 1985
Continents of Continents of
human origin human
invasion
Adding humans to the mix
Earliest H.
erectus
130,000ya
• Is H. erectus to
blame?
Prehistorically
inhabited impacts on
island endemics
Adapted from Martin, 1985
Continents of Continents of
human origin human
invasion
Loss of large sp.
Moderate
Loss of large sp.
Moderate
Many
Loss of small sp.
Few
Loss of small sp.
Few
Few
Rate of
disappearance
Gradual
Rate of
disappearance
Gradual
Sudden
Extinction order
Oldest
Extinction order
Oldest
Intermediate
Archaeological
evidence
Common
Archaeological
evidence
Common
Rare
Earliest H.
erectus
130,000ya
Prehistorically
inhabited impacts on
island endemics
1
Adding humans to the mix
A long history of extinctions…
• Is H. erectus to
blame?
Region
Earliest H.
erectus
130,000ya
Adapted from Martin, 1985
Prehistoric AD1600
-1899
Pacific
90
Indonesia
& Borneo
--
Indian
Ocean
11
Continents of Continents of
human origin human
invasion
Prehistorically
inhabited impacts on
island endemics
Loss of large sp.
Moderate
Many
Total
Philippines
--
Loss of small sp.
Few
Few
Many
Caribbean
34
Rate of
disappearance
Gradual
Sudden
Mostly sudden
N. Guinea
&
Melanesia
10
Extinction order
Oldest
Intermediate
Youngest
Atlantic
Ocean
Archaeological
evidence
Common
Rare
Often rare
Med. Sea
TOTAL
A long history of extinctions…
Region
Prehistoric AD1600
-1899
AD1900
-1994
3
10
AD1900
-1994
158
A long history of extinctions…
Region
Prehistoric
AD1600
-1899
AD1900
-1994
Pacific
90
28
Pacific
90
28
23
Indonesia
& Borneo
--
0
Indonesia
& Borneo
--
0
2
Indian
Ocean
11
30
Indian
Ocean
11
30
1
Philippines
--
0
Philippines
--
0
1
Caribbean
34
2
Caribbean
34
2
1
N. Guinea
&
Melanesia
10
2
N. Guinea
&
Melanesia
10
2
3
1
Atlantic
Ocean
3
3
Atlantic
Ocean
3
3
Med. Sea
10
0
Med. Sea
10
0
0
TOTAL
158
65
158
65
32
TOTAL
A long history of extinctions…
Region
Prehistoric
AD1600
-1899
AD1900
-1994
Approx. No
endemics
%threatened
endemics
Pacific
90
28
23
290
38
Indonesia &
Borneo
--
0
2
390
22
Indian
Ocean
11
30
1
200
33
Philippines
--
0
1
180
19
Caribbean
34
2
1
140
22
N. Guinea
&
Melanesia
10
2
3
500
10
Atlantic
Ocean
3
3
1
50
50
Med. Sea
10
0
0
--
--
158
65
32
1750
23
TOTAL
What have we done…?
?
2
What have we done…?
Agents of destruction…
• Introduced
?
species
Carries of disease…
A complex problem…
• Introduced
diseases…
diseases…
• Psittacene beak
and feather
disease?
• Trichomoniasis?
Trichomoniasis?
• Others we don’
don’t
know about…
about…?
?
Impacts on native bird densities, Mauna Loa (Hawaii)
10
Impacts on native bird densities, Mauna Loa (Hawaii)
10
7.5
7.5
Rel.
Rel.
Abun.
Abun.
5.0
5.0
2.5
2.5
0
0
0
450
900
Altitude (metres)
1350
1800
0
450
900
1350
1800
Altitude (metres)
3
Impacts on native bird densities, Mauna Loa (Hawaii)
10
Impacts on native bird densities, Mauna Loa (Hawaii)
10
7.5
7.5
Rel.
Rel.
Abun.
Abun.
5.0
5.0
2.5
2.5
0
0
0
450
900
Altitude (metres)
1350
1800
0
450
900
Altitude (metres)
Dobson & Hudson, 1986
Trip through time….
Trip through time….
• Pacific ocean islands
• Polynesians introduced
•
settled over 3000y
Hawaii settled over
2000ya
“[The voyagers] went ashore and
found the land fertile and pleasant,
filled with ‘awa,
awa, coconut trees and
so on, and Hawai’
Hawai’iloa,
iloa, the chief,
gave that land his name. Here they
dwelt a long time and when their
canoe was filled with vegetable food
and fish, they returned to their
native country with the intention of
returning to Hawai’
Hawai’i-nei,
nei, which they
preferred to their own country”
country”
•
1350
1800
Dobson & Hudson, 1986
3200 sp arthropod, cats,
dogs, sheep, pigs,
flightless geese, horses,
black rats, goats,
mongooses…
mongooses….
What would have
happened if they never
built that canoe…
canoe…?
Trip through time….
• Easter Island settled
300AD
• Forest that had been
•
•
present for >33,000y was
cleared within 1200y
Today <25% of the 200
vascular plants are native
What happened to the
people…
people….?
4
IAS resource…a case in point
• Lac Alaotra
• The largest lake on
•
Antsiranana
/
Ankarana
Joffreville
the island…
island…
23,000ha of
marsh zetra
Boriziny
Mahajanga
Tsarahasina
Ankazomborona
Mampikony
Tsararano
Ankijabe
Antanandava
Fenoarivo Atsinanana
Lac Alaotra
Ambatondrazaka
Toamasina
Antanambao
Brickaville
Ambatovy
Beforona
Moramanga
Ambositra
Ranomafana
Fianarantsoa
Corridor Nord
#
Mananjary
Ambalavao
Corridor Central
Corridor Sud
#
Isalo
Andringitra
Manakara
LÉGENDE
Zones Strategiques d'Interventions (ZSI)
Zone de Promotion des EFE
Ecosystèmes prioritaires
Forêt littorale et moyenne altitude
Forêt littorale
Forêt dense sèche
Marecages
Lacs
Route nationale
Fianarantsoa Bureaux LDI
IAS resource…a case in point
• 80% surface area
•
•
• The invasive
loss…
loss…burning
continues
Endangered Meller’
Meller’s
duck Anas melleri
Displacement of
genus Paratilapia
…& the Critically
Endangered Lac
Alaotran gentle
lemur Hapalemur
Fibata
Manage rice fields
fibata…
fibata…
• “…So
“…So the people
light a fire to
reveal the fish
resting
underneath, the
fibata,
fibata, that live
in the zetra.
zetra.”
Don't know
Fishing
Ignorance
Reasons given
•
IAS resource…a case in point
Accidents
Bandro
No reason
Discontent
Zebu pasture
Tilapia
Paths
Fishing zones
0
10
20
30
40
50
60
70
80
90
No. Respondents
griseus alaotrensis
IAS resource…a case in point
• “…today
“…today I could
5
Fish catch (seau)
earn 20,000
Ariary or 2000
Ariary”
Ariary”
• …and in Mauritius?
• Gorgeous guava jam
• $3 million annual
Variability in fish
catches
4
3
2
income
1
0
Minimum catch
Price obtained (Ariary)
30000
Variability in
income received
But that’s Madagascar….
Maximum catch
• >1000 livelihoods on
the line
• ….and we wonder
why we are battling
alone?
20000
10000
One seau fish (c10kg)
5
In summary…
Are species ever out of danger?
• Extinction is a natural process but the rate is in
•
•
•
•
•
override
HumanHuman-precipitated extinctions on islands are
not a recent phenomenon
Predation by humans historically the key
threat…
threat…now its introduced species and disease…
disease…
Key threat identification is complex
Cannot afford to adopt a purely biological
approach to threats to island biodiversity
…and one final point…
point…
The Costa Rican Golden
toad
How much could they have in
common???
The Mauritius pink
pigeon
6