Viability of species in fragmented
landscapes
- implications for restoration
Ilkka Hanski
Metapopulation Research Group
University of Helsinki
Biodiversity on Earth
Category
Vertebrates
Invertebrates
Number of species
60,000
1,200,000
Plants
300,000
Lichens
10,000
Mushrooms
16,000
Brown algae
3,000
TOTAL SPECIES
1,6 million
There are likely to be 7-10 million multicellular species
Global extinction rate
Extinctions per species per million years
Source: ccc.maweb.org
Rate of extinctions
percentage of species going extinct in 100 years
Extinctions per species per million years
Past: 0.001%
Present: 1%
2050: >10%*
*of
the ~63,000 species of vertebrates, about 20% are threatened
Global threats to biodiversity
Mammals
Amphibians
Birds
Habitat loss
Over-exploitation
Invasive spp
Human disturb.
Pollution
Natural disasters
Changes in dynamics
Incidental mortality
Disease
Persecution
Percentage of species affected
Extensive habitat conversion
Millenium Ecosystem
Assessment
Oulanka National Park
Finnish-Russian border
lakes
Just habitat loss,
or habitat loss and fragmentation?
Lenore Fahrig
“considering habitat configuration independent
of habitat amount is unnecessary“
(Fahrig 2013, Journal of Biogeography)
THIS TALK
• Habitat fragmentation matters, and this is important
for habitat restoration
• Why does habitat fragmentation matter?
• Assessing the value of individual (possibly restored)
habitat fragments for the landscape-level viability of
species
• Spatial distribution of conservation/restoration effort
• The third-of-third rule
Problem in showing the fragmentation effect
The total amount of habitat and the
degree of fragmentation are typically correlated
Same amount of habitat fragmented
into 20 versus 320 fragments
Habitat quality weakly
spatially correlated
Rybicki & Hanski 2013 Ecology Letters
Habitat quality weakly
spatially correlated
Habitat quality strongly
Habitat spatially
strongly spatially
correlated
correlated
Rybicki & Hanski 2013 Ecology Letters
Why does fragmentation matter?
100%
10%
50%
30%
Pardini et al. 2010 Plos ONE
10% cover
30% cover
50% cover
Photos from Renata Pardini
100%
10%
50%
30%
Pardini et al. 2010 Plos ONE
The three-toed woodpecker
1B
2B
0.15

Density of the woodpecker
p
1A
extinction threshold
0.20
*
0.10
3D
2A
3B
0.05
3C
3A
0.00
0
50
100
150
200
250
300
350
M
Quality of forest landscape
Pakkala et al. 2002
400
Incidence of occupancy
1
0.8
0.6
0.4
0.2
more
fragmented
landscapes
- 3
- 2.5
less
fragmented
landscapes
- 2
- 1.5
- 1
- 0.5
0
log10 Metapopulation capacity (  M )
Hanski & Ovaskainen 2000 Nature
How to include the fragmentation effect
into the species-area relationship?
Habitat quality weakly
spatially correlated
Habitat quality strongly
Habitat strongly
correlated
spatiallyspatially
correlated
Rybicki & Hanski 2013 Ecology Letters
SA R, the species-area relationship
log S  log c  z log A
R2 = 0.94
R2 = 0.24
Hanski et al. 2013 PNAS
The species-fragmented area relationship (SFA R) –
a model that takes into account habitat fragmentation
log S  log c  z log A  b
1
Hanski et al. 2013 PNAS
SA R
R2 = 0.24
SFA R
R2 = 0.94
Hanski et al. 2013 PNAS
Photos courtesy of Gustavo Zurita
Sub-tropical forest birds in the
Atlantic forest region in S America
SA R
SFA R
z = 1.38
R2 = 0.65
R2 = 0.81
Hanski et al. 2013 PNAS
Assessing the value of individual habitat
fragments for landscape-level
viability of species
Spatially realistic metapopulation theory
Hanski & Ovaskainen (2000, Nature)
Ovaskainen & Hanski (2004, in Hanski & Gaggiotti)
• Finite number of habitat patches
• Patch area and connectivity effects on local
extinction and recolonization
• Habitat quality effect via effective patch carrying
capacity
• Extension: habitat quality and local adaptation
(Hanski et al. 2011 AmNat)
The metapopulation capacity of
the network is 10.3
The metapopulation capacity of
the network is 10.3
Increasing the quality of patch #1
5-fold increases the metapopulation
capacity by 14%
The metapopulation capacity of
the network is 10.3
Patch #1 quality 5-fold
Patch #1 area 5-fold
14%
77%
The metapopulation capacity of
the network is 10.3
Patch #1 quality 5-fold
Patch #1 area 5-fold
Patch #2 area 5-fold
14%
77%
5%
The metapopulation capacity of
the network is 10.3
Patch #1 quality 5-fold
14%
Patch #1 area 5-fold
77%
Patch #2 area 5-fold
5%
Add new patch (open circle) 18%
A model example of restoring habitat quality
Hanski 2000, Ann Zool Fennici
300
70
250
60
50
200
Frequency
Number of sites occupied
Slow decline of specialist forest species
in a highly managed forest landscape
150
100
40
30
20
50
10
0
0
-20
0
20
Years
40
60
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Forest site quality
Hanski 2000, Ann Zool Fennici
Number of sites occupied
The effect of improving forest stand quality by 10%
uniformly across the forest landscape
300
300
250
250
200
200
150
150
100
100
50
50
0
10% increase
0
-20
0
20
40
60
-20
Years
0
20
40
60
Years
60
60
50
Frequency
50
40
40
30
30
20
20
10
10
0
0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Forest site quality
Number of sites occupied
Concentrate the same restoration effort within 10% of
the forest landscape
300
300
250
250
200
200
150
150
100
100
50
50
0
0
-20
0
20
40
60
-20
Years
Frequency
20
40
60
Years
70
30
60
25
50
0
20
40
15
30
10
20
5
10
0
0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Forest site quality
Number of sites occupied
Concentrate the same restoration effort within 10% of the
forest landscape, close to existing high quality stands
300
300
250
250
200
200
150
150
100
100
50
50
0
0
-20
0
20
40
60
-20
Frequency
Years
20
40
60
Years
60
30
50
25
40
20
30
15
20
10
10
5
0
0
0
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Forest site quality
0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4
Forest site quality
A
Number of sites occupied
Forest restoration
started now
300
250
200
150
100
50
0
Number of sites occupied
-20
B
Number of sites occupied
Number of sites occupied
20
40
60
300
250
250
200
200
150
150
100
100
50
50
0
0
0
20
40
60
300
300
250
250
200
200
150
150
100
100
50
50
0
-20
0
20
40
60
-20
0
20
40
60
-20
0
20
40
60
0
-20
D
0
300
-20
C
Forest restoration
started after 30 years
0
20
40
60
300
300
250
250
200
200
150
150
100
100
50
50
0
0
-20
0
20
Years
40
60
Years
Third–of-third
30% cover
Conservation landscape
10% cover
30% cover
Hanski 2011 Ambio
Third–of-third
30% cover
Conservation landscape
10% cover
30% cover
Hanski 2011 Ambio
Third-of-third
• Multi-use conservation landscapes, which are so large that
they retain demographically and genetically viable
metapopulations (~ 10,000 ha)
• Retain large-scale connectivity if conservation landscapes are
spread across the country and cover a third of the total area
• Retain ecosystem services
• Bring biodiversity closer to people
Hanski 2011 Ambio
Conclusions
• Fragmentation makes a difference because species have
extinction thresholds
• Species-fragmented area relationship (SFAR) takes the
fragmentation effect into account
• Metapopulation models may be used to assess the value of
existing or restored habitat fragments to the capacity of
fragmented landscapes to support viable metapopulations
• Third-of-third rule