Extinction debt and colonization credit in
highly fragmented forest landscapes
Nitra, 27.05.15Jens Kolk & Tobias Naaf
• Question: Do historical land cover changes influence present-day plant species richness of temperate deciduous forests?
• Dramatic changes:
• Extinction debt and colonization credit
Introduction
2000 – 2012 Brazil 1780 – 1880 Germany, PrignitzData according to Hansen et al. 2013 Kolk & Naaf 2015, Biol. Cons. 182
Extinction debt
• Time-delayed extinctions, debt to be paid in future
Habitat loss /fragmentation
New equilibrium
Extinction debt
Relaxation time
Time
Speci
es
rich
ness
Where are we right now?
ED not paid at all?
ED paid half?
ED paid completely?
[adapted from Kuussaari et al. 2009, TREE 24]
Colonization credit
• Time-delayed colonization, credit depleted in the future
Where are we right now?
CC still there?
CC depleted half?
CC depleted completely?
Colonization credit
Relaxation time
Time
Speci
es
rich
ness
Habitat creation
New equilibrium
[adapted from Kuussaari et al. 2009, TREE 24]
Landscape level scheme
Richness in equilibrium habitat
Colonization credit
Time
Speci
es
rich
ness Ancient forest
Post-agricultural forest
Habitat creation
Extinction debt
Habitat fragmentation
Raw difference
Ancient forest: Continuously forest since at least 1780
Post-agricultural forest: Recently established on agricultural land
Study area
• Flat terrain
• Intensive agriculture
• 5% deciduous forest cover
• Main deciduous tree species– Oak (Quercus robur)– Beech (Fagus
sylvatica)– Alder (Alnus
glutinosa)
©Neuenhausen-prics.de
©Groundhopping-Merseburg
Land use history
Georeferencing ~ 350 ticks
Rectification
Overlay with 2008 Aerials + TK25 map
Schmettau Map 1767-1787
Digitize and classify forests
Prussian Gov. Map ca. 1880
1780
• Large areas covered with deciduous forests
• Approx. 1000 Patches
• 32% cover¯0 5 10
Kilometers
2008
• 92% Loss• 6000 Patches =
Fragmentation
• 5% cover– 36% ancient– 64% post-
agricultural ¯0 5 10Kilometers
ancient
post-agricultural
Extinction debt of forest specialists in ancient forests
Extinction debt
• Land use history data• Specialists occurrence in 104 patches• Hypothesis:
Strong relationship with historical patch configurationSp
ecie
s ric
hnes
s
Patch areaPatch connectivity
Weak relationship with present-day patch configuration
[adapted from Kuussaari et al. 2009, TREE 24]
Convallaria majalis
Sanicula europaea
Paris quadrifolia
ED: Results
• Present day configuration always explains SR better
• However, historical connectivity significant
β = 0.12, P = 0.023
P < 0.001 n.s.
Forest specialists richness dependent on present-day area and connectivity
Kolk & Naaf 2015, Biol. Cons. 182 Method: Negative binomial GLM
ED: Discussion
• Extinction debt almost paid
• Historical connectivity last glimpse of ED
• Massive area loss in short time
• Fragmentation after 1880
1780 1880 2008
1780 1880 2008
Deciduous forest area
Number of Patches
ED: Conclusions
• Rapid payment of extinction debt
Habitat loss /fragmentation
New equilibrium
Extinction debt
Relaxation time
Time
Speci
es
rich
ness
Where are we right now?
ED not paid at all?
ED paid half?
ED paid completely?
[adapted from Kuussaari et al. 2009, TREE 24]
ED paid completely!(almost)
Colonization credit of forest specialists in post-agricultural forests
Colonization credit
• Specialists in 110 post-agricultural patches• We now know: Extinction debt largely
paid• Predict SR using the ancient patches• Hypothesis:
Speci
es
rich
ness
Time, Patch connectivity
Observed richness in post-agricultural forest patches
Predicted richness from ancient equilibrium patches
Colonization
credit
CC: Results
• Mean colonization credit 4.7 species• Up to 9 in highly isolated patches• Credit for specialists was not smaller in
older patchesP = 0.341
P < 0.001
CC: Conclusions
• Recovery may take several centuries (if ever)
Where are we right now?
CC still there?
CC depleted half?
CC depleted completely?
Colonization credit
Time
Speci
es
rich
ness
Habitat creation
New equilibrium
[adapted from Kuussaari et al. 2009, TREE 24]
CC still there!
CC remains
Summary
Question: Do historical land cover changes influence present-day plant species richness of temperate deciduous forests?
• Yes, mainly due to colonization credit
• Extinction debt may be paid rapidly
• Colonization may take a long time
• Land use history is important
Thank you for your attention!