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Several over- and underpasses targeted particularly for larger wildlife has been built or are currently in construction in Sweden. These varies in design, for example dimensions, fencing/screening, and vegetation and other habitat components in and around passages. Some design parameters, most notably size, are highly cost driving, and better knowledge of design details is needed to make future constructions more cost-efficient.
There is generally a lack of rigid scientific support (also internationally) for the available construction guidelines, and there is an obvious risk that wildlife passages are built too small to fulfil their intended function, or conversely that they are built too large for precautionary reason. In either case, money may be wasted.
Monitoring of wildlife passages is largely neglected in Sweden and abroad, or conducted at a very basic level, not allowing to relate to set targets or making cost-efficiency comparisons. Furthermore, monitoring results from different passages cannot be easily compared or scientifically reported. Accordingly, opportunities to gain important knowledge are missed.
However, Trafikverket has now agreed on a standardized monitoring method, that allows the joint analysis of different passages that is necessary to produce new, scientifically founded construction guidelines.
Sandsjöbacka ecoduct, south of Gothenburg. Photo: © PEAB Air.
In this subproject we will monitor wildlife’s use of a number of over- and underpasses, and compare performance depending on size and design, and to a degree on siting and landscape type/geographical region.
Monitoring method will be similar between passages to facilitate direct comparison. As far as possible, data should be gathered from (and in cooperation with) monitoring studies conducted within the respective investment project.
Field methods should include studies of animal movements and behaviour near and through the crossing (for example photo traps, sand beds and snow tracking), following standardized methods. Effect sizes will be compared with the cost of each improvement type.
The results will be published scientifically.
This subproject produces values of the efficacy of wildlife over- and underpasses in connecting wildlife between roadsides. Efficacy is separated between species and categories of animals (age and gender) to put light on population level impacts.
The most important outcome is that the results enables cost-efficiency comparisons between different crossing types and designs, and ideally (together with previous subprojects) to point out the optimal design for a standard design for wildlife passages.
Data collection (photo trapping) is ongoing in and around the following bridges:
Road 31 Tenhult
Large moose underpass at national road 31 near Tenhult.
Road 31 Tenhult
Four minor passages at national road 31 near Tenhult.
Road 11 Vomb
Red deer underpass at national road 11 near Vomb.
Road 73 Älby
Moose bridge at national road 73 Älby, Nynäshamn.
Reindeer bridge over Haparandabanan railway at Sangijärvi.
Three minor bridges at Haparandabanan railway between Kalix and Haparanda.
Road E10 Mertainen
Reindeer bridge over road E10 at Mertainen.
Road E20 Sandsjöbacka
Ecoduct and cattle tunnel at E20 at Sandsjöbacka.
The following existing bridges and tunnels are candidates for study objects (the list is not exhaustive):
Road 45 Kungälv-Trollhättan
Four combined fauna/road overpasses at national road 45 between Kungälv and Trollhättan (*Mats Lindqvist).
Reindeer bridge over Malmbanan railway at Råtsi (*Katarina Andersson/Malin Delvenne).
Reindeer bridge over railway at Aitik mine (*Katarina Andersson/Malin Delvenne).
Longer road tunnels
Longer road tunnels, for example at E18 (Ullbro, Frösvi), E20 (Jeriko), road 265 (Löttinge).
New wildlife passages constructed during the project period are also candidate study objects, for example:
Road E20 Hova
Fauna overpass and bridge over stream at E20 Hova.
Road E6 Hallandsås
Fauna underpass under E6 at Hallandsås.
Road E65 Lemmeströtorp
Red deer bridge over motorway E65 at Lemmeströtorp.
Road 21 Ekeberg
Fauna bridge over national road 21 at Ekeberg (between Kristianstad and Hässleholm).
Road E22 Norra Binga
Fauna passage at road E22 Norra Binga (east Blekinge).
Road E20 Kristineholm-Bälinge
Two fauna underpasses at road E20 Kristineholm-Bälinge.
Road E20 Tollered-Ingared
Fauna passage at intersection at E20 Tollered-Ingared.
Road 23/34 Hamra
Smaller fauna passage under national road 23/34 at Hamra (Åtvidaberg).
Publications and outreach
The subproject Over- and underpasses for larger wildlife has resulted in: