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Metapopulation Research Group
Survival of species in fragmented forest landscapes
Ilkka Hanski
Metapopulation Research Group
Contents
• How to assess the consequences of fragmentation in dynamic landscapes?
• Time delay in metapopulation response to changing environment
• Extinction thresholds and implications for biodiversity conservation
• Conclusion: What is needed to protect biodiversity in our boreal forests?
fragmentation threatensbiodiversity
Metapopulation Research Group
How to estimate isolation and hence the effect of fragmentation?
• Isolation has a temporal as well as a spatial component --- current isolation versus how did that isolation evolve
• Solution: construct a model with which the occurrence of focal species in all parts of the landscape is predicted, including the focal fragments
• Simulate the occurrence of the species assuming the observed history of fragmentation
Metapopulation Research Group
1945
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1955
Metapopulation Research Group
1965
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1975
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1985
Metapopulation Research Group
1995
Metapopulation Research Group
Probability for a particular forest fragment to be occupied
year
1940 1950 1960 1970 1980 1990 2000 20100.0
0.2
0.4
0.6
0.8
1.0
Fragment 2
Fragment 9
Fragment 1
Fragment 5
Metapopulation Research Group
Explaining the occurrence of four species of old-growth bracket fungi in spruce forest
fragmentsLogistic regression model
Isolation history Decaying wood
p p
Amylocystis lapponica <0.001 <0.001
Fomitopsis rosea <0.001
Phlebia centrifuga 0.056 <0.001
Cystostereum murraii 0.037
Note! Current isolation nor time since isolation did not explain the occurrence of the species when analysed separately
Metapopulation Research Group
message # 1
To understand a dynamic process, such as the effect of habitat fragmentation on
biodiversity, it is helpful to employ a dynamic model
Metapopulation Research Group
Metapopulation dynamics in dynamic landscapes
• How long is the delay in metapopulation response to change in landscape structure?
• Which factors influence the length of the time delay?
Metapopulation Research Group
Metapopulation Research Group
Decline in the amountof habitat
Metapopulation response:
thick line = equilibriumthin lines = predicted changes
Metapopulation Research Group
M et apopulat ion r esponse t o habit at loss
Det er minist ic r esult
0.5 1 1.5 2 2.5 3
2.5
5
7.5
10
12.5
15
17.5
A ver age and 90% confi dence int er vals of 200 simulat ions
Tim
e d
elay
common species
species doomed to extinction
Metapopulation Research Group
0 0.5 1 1.5 2 2.5 3
0
0.5
1
1.5
2
2.5
3
0 0.5 1 1.5 2 2.5 3
0
0.5
1
1.5
2
2.5
3
1. Strength of the perturbation
Transient time depends on three factors
Short transient time Long transient time
Metapopulation Research Group
2. Species and landscape specific turnover rate
Transient time depends on three factors
Short transient time Long transient time0.5 1 1.5 2 2.5 3
0.5
1
1.5
2
2.5
3
0.5 1 1.5 2 2.5 3
0.5
1
1.5
2
2.5
3
Metapopulation Research Group
3. Distance to the extinction threshold
Transient time depends on three factors
Short transient time
Long transient time
M M M
Short transient time
Metapopulation Research Group
message # 2
Time delay in metapopulation response to habitat loss and fragmentation is especially long in the case of the threatened species
Metapopulation Research Group
Predicted change in the shape of the ‘commonness’ distribution following environmental change
Number of speciesthat have gone extinct
Extinction debt =Number of speciesthat will go extinct
Metapopulation Research Group
Area of old-growth
forest in Finland
S Finland 0.6%
N Finland 10.4%
Entire Finland 5.5%
Metapopulation Research Group
Threatened beetles in boreal forests (based on data and analysis by Pertti Rassi)
SW coastal Finland
1 2 3 4 5 6 7 8
Per
cent
age
of r
egio
nally
extin
ct s
peci
es
0
10
20
30
40
50
60
70
80
90
NE inland Finland
8
58
8545
68
48
33
12
19
5734
8
24
2
SW coastal Finland NE inland Finland
1 2 3 4 5 6 7 8
Per
cent
age
of n
atur
al-li
kefo
rest
rem
aini
ng
0
2
4
6
8
10
12
14
16
18
Metapopulation Research Group
message # 3Extinction debt in Finnish forests
• Based on the recent red data book, we may estimate that there are nearly 2,000 extinct or threatened species in Finnish forests
• In addition, there is a large and rapidly increasing number of regionally extinct or threatened species in southern Finland
Metapopulation Research Group
The response of species to a change in habitat/landscape quality
Lajis
ton
vast
e
Ym päristön m uutos Ym päristön m uutos
Metapopulation Research Group
0
0.2
0.4
0.6
0.8
1
1 10 100 1000
Lahopuun tilavuus, m3/ha
Asu
ttuj
en p
uide
n os
uus,
%
Leptusa pulchella, asuttujen puiden osuus sopivista puista(yksi piste = asuttujenpuiden osuus yhdessä metsikössä)
50
28 metsikköä
124 puuta
7 metsikköä
58 puuta
9 metsikköä
91 puuta
50
Punttila, Siitonen & Lindström, julkaisematon
Metapopulation Research Group
0
0.2
0.4
0.6
0.8
1
1 10 100 1000
Lahopuun tilavuus, m3/ha
Asu
ttuj
en p
uide
n os
uus,
%
28 metsikköä
124 puuta
Olisthaerus substriatus, asuttujen puiden osuus sopivista puista(yksi piste = asuttujen puiden osuus yhdessä metsikössä)
7 metsikköä
58 puuta
9 metsikköä91 puuta
5050
Punttila, Siitonen & Lindström, julkaisematon
Metapopulation Research Group
The three-toed woodpecker - an example of the treshold condition at the regional scale
0 50 100 150 200 250 300 350 4000.00
0.05
0.10
0.15
0.20
*
M
3A
3C
3B
3D2A
2B1B
1A
p
Metapopulation Research Group
message # 4
The response of species to a change in habitat quality is typically non-linear and involves
a threshold
Metapopulation Research Group
The new forestry guidelines -is this the solution?
If commercial forestry will occupy all the non-protected forest land, and if all this
forested land will be managed according to the guidelines, the new guidelines may
represent a change to the worse
Metapopulation Research Group
The slow process of disappearence of endangered species in the current forest landscape
Years
-20 0 20 40 60
Num
ber
of s
ites
occu
pied
0
50
100
150
200
250
300
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Fre
quen
cy
0
10
20
30
40
50
60
70
The outcome of comprehensive implementation of the new forestry practice
Years
-20 0 20 40 60
Nu
mb
er
of
site
s o
ccu
pie
d
0
50
100
150
200
250
300
Years
-20 0 20 40 600
50
100
150
200
250
300
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Fre
qu
en
cy
0
10
20
30
40
50
60
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40
10
20
30
40
50
60
Let us focus the same conservation effort within 10% of forested land
Years
-20 0 20 40 60
Num
ber
of s
ites
occu
pied
0
50
100
150
200
250
300
Years
-20 0 20 40 60
0
50
100
150
200
250
300
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Fre
quen
cy
0
10
20
30
40
50
60
70
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40
5
10
15
20
25
30
Conservation measures within 10% of forested land but now located next to the currently most valuable forest stands
Years
-20 0 20 40 60
Num
ber
of s
ites
occu
pied
0
50
100
150
200
250
300
Years
-20 0 20 40 60
0
50
100
150
200
250
300
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Fre
quen
cy
0
10
20
30
40
50
60
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.40
5
10
15
20
25
30
Metapopulation Research Group
Concluding messages
• Our forests have a large extinction debt• It is cost-effective to act now• The new measures introduced in Finland
(retention trees, protection of small patches of key habitats, etc.) may make the situation worse if all the forested land will be treated similarly
• It would pay to concentrate the conservation efforts… basically, we need more area out of commercial forestry