Helping wild animals to cross Switzerland safely

In our region, too, wild animals sometimes travel long distances. It is often young animals that leave their pack or family in search of their own territory. Such migrations keep populations healthy: they enable new settlements and genetic exchange. With climate change, this is becoming even more important, as species must adapt to changing conditions. Accordingly, national and international guidelines require the federal government and the cantons to improve the connectivity of habitats.

Obstacles in the cultural landscape 

Migrating animals are often unfamiliar with the area. They therefore move cautiously and seek cover wherever possible – for example, in woods or along hedgerows. In Switzerland, where the landscape is heavily fragmented, numerous obstacles hinder their movement: motorways, railway lines, built-up areas, fences and illuminated areas. Such barriers force animals to take detours, increase the risk of road crossings or completely sever habitats. 

To better understand where wild animals prefer to migrate, there is the ‘Wildlife Connectivity System’ (see, among others, the Environment Series No. 326 ‘Wildlife Corridors in Switzerland’). It describes key movement routes across the country. Wildlife corridors have been designated at particularly critical points. In Switzerland, there are 304 wildlife corridors of supra-regional importance – fewer than a third of these remain intact today. Many corridors are significantly impaired, and around 50 are considered largely disrupted. 

To improve the situation, measures are needed in the right places. Wildlife bridges over motorways are visible – but smaller interventions often have an effect too. It is important that animals find sufficient quiet areas during their migration and are able to orientate themselves. Guiding structures such as hedges, fallow land or wooded watercourses lead wildlife to suitable crossing points. 

Technical solutions can also help: wildlife warning devices or improved visibility along roads ensure that drivers spot animals sooner – and vice versa. This reduces the risk of accidents. Collisions with wildlife cause significant damage to property every year and can be dangerous for people. AXA estimates the annual cost of such damage at over 11 million Swiss francs.

Planning at cantonal level 

For measures to be effective, good planning is essential. We help cantons to identify and prioritise key sections of the wildlife connectivity network – where the need and the benefits are greatest. On behalf of the Bern Game Inspectorate, we are currently assessing the connectivity of the network and evaluating the condition of the 33 inter-regional wildlife corridors in the Bern region. Input from gamekeepers is also crucial here: they are familiar with the wildlife routes used, obstacles and waiting areas. For each corridor, we produce a fact sheet containing the key facts and specific proposals for measures. These documents help to prevent unintended disruption to the corridors and to capitalise on opportunities for improvement at an early stage. 

In the canton of Solothurn, we carried out similar assessments around 20 years ago. Today, we are reviewing those assessments and formulating additional measures. In addition to site visits, we are making increasing use of geodata, such as maps of wildlife collisions, LiDAR data for woody vegetation as guiding structures, or landscape permeability models from the company Nategra. However, on-site inspections remain crucial: this is the only way to identify small barriers such as walls or fences and develop concrete solutions. The use of a drone provides additional insights in this regard.

Example: the Klus bottleneck near Balsthal 

A wildlife corridor does not have to be an untouched natural area. What matters is that animals can actually use it. A particularly challenging section is located at the Balsthal gorge (Canton of Solothurn). The corridor is intended to link the Jura forests to the east and west of the gorge, but is severely restricted by industrial buildings with fences, a motorway, a railway line, residential buildings and the built-up Dünnern stream. The ‘Flood Protection and Revitalisation of the Dünnern from Oensingen to Olten’ project opens up new possibilities. On behalf of the Office for Forestry, Hunting and Fisheries, we investigated how the corridor could be further improved alongside the revitalisation work. 

The starting point was a vision for connectivity: the revitalised Dünnern is to serve as a quiet resting area. To the east, wildlife should be able to cross the motorway slip road and railway line at a suitable point. To the west, the upgraded Dünnern should be easily accessible via open spaces along the watercourse. 

Building on this, we developed two options: one with a wildlife crossing and one without. In both options, improvements along the Dünnern are central; in addition, connectivity features in the open spaces will be enhanced. In the option without a wildlife crossing, a combination of measures (including speed reduction, wildlife warning systems and terrain modifications) is intended to make crossing safer. With a crossing, animals would be guided over a bridge at the same location. 

Both options significantly improve the situation. Whilst an overpass would reduce collisions with wildlife more effectively, both approaches are equally effective in terms of the corridor’s actual function. Furthermore, a wildlife bridge would restrict future options for road expansion and would be more expensive overall. The option without an overpass is therefore currently the more pragmatic solution.