An approach to defragmentation in
low-contrast landscapes
Jan Olof Helldin, Calluna AB, Sweden
&
Andreas Seiler, Grimsö Wildlife Research Station, SLU, Sweden
1
Current focus on constructing
large fauna passages
Photo: Kari Gunson
(maximizing usage by wildlife)
Photo: Google Maps
Current focus on constructing
large fauna passages
$ $
€
€
$
Photo: Kari Gunson
(maximizing usage by wildlife)
$
Photo: Google Maps
Concept of ecological corridors
Source: Jedrzejewski et al. 2005
– Poland
Concept of ecological corridors
Source: BUND.net
– Germany
Concept of ecological corridors
Source: Caltrans
– California
How to do in low-contrast landscapes?
How to do in low-contrast landscapes?
8
?
?
?
?
?
?
Each crossing structure has a catchment area or catchment
distance
Depend on species and ambition
•Daily movements = √HR
•Dispersing animals = 7 x √HR
HR = home range area
Source: Bissonette & Adair, Biol.Cons. 2008
Each crossing structure has a catchment area or catchment
distance
Depend on species and ambition
•Daily movements = √HR
•Dispersing animals = 7 x √HR
HR = home range area
Source: Bissonette & Adair, Biol.Cons. 2008
Each crossing structure has a catchment area or catchment
distance
Depend on species and ambition
•Daily movements = √HR
•Dispersing animals = 7 x √HR
HR = home range area
Source: Bissonette & Adair, Biol.Cons. 2008
Each crossing structure has a catchment area or catchment
distance
Depend on species and ambition
•Daily movements = √HR
•Dispersing animals = 7 x √HR
HR = home range area
Source: Bissonette & Adair, Biol.Cons. 2008
Examples
√HR
Roe deer
2 km 14 km
Moose
4 km 28 km
7x√HR
Each crossing structure has a catchment area or catchment
distance
Depend on species and ambition
•Daily movements = √HR
•Dispersing animals = 7 x √HR
HR = home range area
Source: Bissonette & Adair, Biol.Cons. 2008
•Distance between passages = 2 x catchment distance?
Examples
√HR
Roe deer
2 km 14 km
Moose
4 km 28 km
7x√HR
Ecological connectivity through non-wildlife brigdes and culverts
Source: Olsson & Seiler, IENE 2012
Wildlife adaptation of non-wildlife crossing structures
Structures
Vegetation
Photo: Mats Lindqvist
Screening
Minimize traffic
Photos: Rijkswaterstaat
Manage light
Limited effectiveness (various degrees)
= smaller catchment distance
Full effectiveness
= max catchment distance
Remaining barriers
Limited effectiveness (various degrees)
= smaller catchment distance
Full effectiveness
= max catchment distance
A SLOSS trade-off!
(SLOSS = Single Large Or Several Small)
Strategy for connectivity
Assume that animal movements are dispersed
Optimizing usage instead of maximizing
1. Identify the ecological connectivity delivered by non-wildlife
brigdes and culverts
2. Further promote connectivity by adapting non-wildlife
crossing structures
3. Identify remaining, unresolved barriers
4. Mitigate these barriers, if needed to meet set goals
5. Make a SLOSS trade-off
Set a goal for connectivity
Goal reached by existing nonwildlife crossing structures?
yes
No mitigation
needed
yes
Adapt crossing structures
no
Can goal be reached by
adapting non-wildlife
crossing structures?
no
Goal best reached by single
large or several small (SLOSS)?
Select the most costefficient solution
Outcome depends on:
• target species or target habitat
• landscape structure (coarse or fine grained, high or low contrast)
Food for discussion
1. Could this strategy actually be better in low-contrast
landscapes?
2. Can this strategy be of value also in high-contrast
landscapes? (Do animals actually follow habitat corridors like
we expect them to do?)
3. Output depend on goals; deeper analysis of goals needed!
4. Output probably depend on landscape; better analysis of
landscape structure needed!
Research programme:
and conducted by:
financed by: