metapopulation research group survival of species in fragmented forest landscapes ilkka hanski

Metapopulation Research Group

Survival of species in fragmented forest landscapes

Ilkka Hanski


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


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


1945


1955


1965


1975


1985


1995


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


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


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 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?


Decline in the amountof habitat

Metapopulation response:

thick line = equilibriumthin lines = predicted changes

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


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


2. Species and landscape specific turnover rate


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


3. Distance to the extinction threshold


Short transient time

Long transient time

M M M

Short transient time


message # 2

Time delay in metapopulation response to habitat loss and fragmentation is especially long in the case of the threatened species


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


Area of old-growth

forest in Finland

S Finland 0.6%

N Finland 10.4%

Entire Finland 5.5%


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


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


The response of species to a change in habitat/landscape quality

Lajis

ton

vast

e

Ym päristön m uutos Ym päristön m uutos


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


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


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


message # 4

The response of species to a change in habitat quality is typically non-linear and involves

a threshold


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


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


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

metapopulation research group survival of species in fragmented forest landscapes ilkka hanski

Documents

biodiversity slide

metapopulation response

particular forest fragment

current isolation

occurrence of focal

species of old

consequences of fragmentation

effect of fragmentation