10.3.3 Maintenance of wildlife crossing structures
Wildlife crossings (also named fauna passages) are transversal structures located under or over the linear transport infrastructure constructed or modified to provide safe crossing points for animals and/or to connect habitats on both sides of the linear infrastructure. Main types of wildlife crossings are:
- Ecoducts (green/landscape bridges)
- Wildlife and multi-use overpasses
- Canopy bridges (tree-top overpasses)
- Viaducts
- Wildlife and multi-use underpasses
- Modified culverts
- Amphibian tunnels
Wildlife crossings must be regularly inspected and maintained to ensure their long-term performance. Structural points as well as ecological features related to soil, vegetation, wildlife refuges or human uses could have a major effect on fauna passage effectiveness and must be appropriately maintained. Land uses and environmental changes in adjacent areas may also radically modify their use by wildlife.
All types of wildlife crossing, including under and overpasses and culverts modified to enhance wildlife use should be included in the inventory and the maintenance plan. Maintenance tasks may vary widely according to the type of structure and must be based on standards provided in the project (see Box 3).
Some passages are specific for wildlife, while others are multi-use and combine wildlife crossing with drainage, cattle routes, pedestrian paths, or even low-intensity traffic roads. Cooperation with water, environmental and land planning authorities, as well as other local stakeholders, is crucial to guarantee their conservation and could assist in reducing maintenance costs.
Special structures, such as big landscape bridges (ecoducts), could require particular management involving local stakeholders. Those structures located in Natural Protected Areas, ecological corridors or with endangered target species should be prioritised and will require additional ecological monitoring by wildlife experts to verify the achievement of their goals.
The following descriptive maintenance task sheets are provided in section 10.4.
Maintenance of ecoducts, wildlife and multi-use overpasses
Maintenance of viaducts, wildlife and multi-use underpasses
Maintenance of modified culverts
Maintenance of amphibian tunnels
10.3.5 Maintenance of verges and other green areas
The main goal for road verges and medians management is to meet standards for road safety. However, most of these elements can also provide aesthetic landscape value and habitats for wildlife. These green areas, including resting areas and other landscaped zones, help enhance Green Infrastructure when they are managed to promote and sustain benefits to biodiversity. Two basic principles apply when enhancing habitats for wildlife:
- Legal obligations for wildlife conservation such as European Directives on Habitats and Birds, require that maintenance tasks do not injure, kill or disturb the breeding sites of endangered species (see list).
- Conflicts with traffic safety and the creation of ‘ecological traps’, attracting animals to areas with high mortality risk, must be avoided with expert help to carefully select the areas where biodiversity could be enhanced and those where wildlife access should be avoided.
Soil and vegetation management is key to attracting or deterring target species because wildlife habitats are defined by those elements. Landscaped green areas along transport linear infrastructure may have positive, neutral, or negative effects depending on how they are designed and managed.
Activities included in green areas maintenance are soil management, sowing, planting, mowing, pruning, replacement, removal and any other task needed to conserve or improve the green area habitats. Maintenance of structures that provide refuges to target species should also be included. A task schedule must be planned considering road safety, climate, soil and vegetation conditions and to provide a mosaic of habitats with different features where they are needed. The schedule must also be adapted to the life- cycles of wildlife target species to avoid any damage during breeding and hibernation periods.
Landscaped area maintenance should include the definition of sections to be managed according to different goals and functions (to reduce hazards to traffic, to enhance wildlife, etc.) identifying stretches that will require different conditions according to these (see Box 4). Conditions established by road and environment regulations must be considered.
Control of invasive alien species (IAS) is a key task to be developed and appropriate maintenance could also provide an essential ecological function in combatting the effects of climate change such as the risks of forest fire spread or flooding.
Site conditions such as weather, ecosystems and target species present in the area will have a strong influence on vegetation management. Cooperating with ecologists will help adapt guidelines in this document to local conditions.
Main aspects to be considered for verge and median biodiversity-friendly management are listed in Box 5.
The following descriptive maintenance task sheets are provided in section 10.4.
Maintenance of habitats for pollinators and other small fauna
Control of invasive alien species (IAS)
10.3.6 Maintenance of ponds and other drainage elements
Drainage systems in roads and railways include perimeter ditches, retention ponds, culverts, and other transversal structures. Ensuring standards for water evacuation and road safety through drainage systems can be combined with enhancing biodiversity by providing habitats for wildlife. Ponds and ditches can host invertebrates and fish, attract amphibians to breed and provide shelter and food for insects, reptiles, mammals and birds. Two basic principles apply when enhancing aquatic habitats for wildlife:
- Legal obligations for wildlife conservation such as European Directives of Habitats and Bird, require that maintenance tasks do not injure, kill or disturb the breeding sites of endangered species (see list).
- Conflicts with traffic safety and the creation of ‘ecological traps’, attracting animals to areas with high mortality risk, must be avoided with expert help to carefully select the areas where biodiversity could be enhanced.
Drainage transversal structures such as culverts, open-span bridges and viaducts can also play a key role in ecological connectivity, providing links for wetlands, channels, rivers, and other aquatic elements of the Green Infrastructure. Drainage elements that can play a role as habitats for wildlife should be identified and specifications for management must be provided.
Maps of aquatic habitats in retention ponds, ditches and other elements of the drainage systems to be inspected and maintained, should be included in a GIS database. Management should be planned primarily to maintain the function of drainage and areas managed to enhance biodiversity should have particular specifications including standards to be met for all features in ponds and drainage elements (including water level variation, water quality, vegetation conditions, etc.).
Water, road and wildlife experts must work together to design successful drainage system maintenance practice.
Main aspects to be considered for drainage systems biodiversity-friendly maintenance are listed in Box 6.
The following descriptive maintenance task sheets are provided in section 10.4.
Management of retention ponds to host wildlife
See also
Maintenance of viaducts, wildlife and multi-use underpasses
Maintenance of modified culverts.
10.3.7 Animal-vehicle collisions (AVC) management
Road and railway traffic accidents involving large animals are increasing in many European regions. Removing carcasses is a significant task for maintenance crews, has health and safety implications and high economic costs. To appropriately record and analyse road traffic accidents involving animals is the basis for identifying hotspots of wildlife road mortality, factors increasing the risk, and the data thresholds at which action to reduce the AVC must be taken.
Investing in appropriate mitigation measures to avoid AVC is cost-effective practice in economic, social and environmental terms. A number of mitigation measures can be applied by road operators, such as improving or reinforcing fences, adapting existing transversal structures to be used by wildlife, and enhancing wildlife awareness signage based upon expert identification of conflict points and assessment of potential solutions.
AVC management should be based on the points listed below.
- Develop practice based on instructions for the whole AVC management process including searching, removing, recording data and undertaking regular expert analyses to determine conflictive road sections and take corrective action.
- Define and apply procedures for removal and destruction of carcasses, or any other treatment according to national Be aware that some animal health regulations could require specific management of carcasses, e.g. strict biosafety conditions exist for wild boar carcass management in regions affected by African Swine Fever.
- Use a system to record roadkill data which allows mitigation measures to be defined from the information (see Box 7). The data recorded from field crews collecting carcasses provides the key basic information. Periodic additional surveys conducted by wildlife experts are needed in sensitive areas crossing habitats with high risk of mortality of small animals (protected areas, river crossings, wetlands, etc.) which are not recorded during regular crew patrolling.
- Provide field crews with procedures and appropriate devices for accurately recording carcasses Other stakeholders may also provide data such as police, traffic authorities, conservation organisations, hunters, etc.
- Define and apply user friendly procedures for recording data about each animal carcass, which include time (date and hour), location (road code, coordinates of the point) and details about the animal (species, sex and age class: adult or juvenile) if known. Local conditions related to the infrastructure or the landscape which help understand why the accidents occur should also be recorded.
- Develop appropriate training for maintenance staff and field crews on data collection and carcass management (see section 10.2; step 5) including guides to identify the species.
- Request regular analyses of the data collected to identify road mortality hotspots, to be undertaken by experts (see Box 8).
- Define the problem: numbers, most affected species, most conflictive periods, etc. )
- Apply road accident clustering methods to identify sections where AVC are more frequent, e.g. KDE+ or any other which has the possibility to define a frequency threshold goal.
- Identify where, when and why accidents cluster using location-specific data as a basis for the definition of appropriate solutions.
- Set the general qualitative or quantitative standards to be met and thresholds of AVC frequency which can vary widely depending on target species and their numbers in the area. This permits identification of priority road sections where thresholds are breached and appropriate mitigation measures must be taken.
- Monitor, evaluate and report successes, needs and conflicts experienced during the management of wildlife road mortality, in order to include this information in future plans.
- Modify the maintenance plan and undertake corrective actions according to results and information gathered and to target species most frequently road Define and schedule additional actions to reduce conflicts (fencing combined with fauna passage, modification of verge and median conditions, etc.) if conflict increases or expands.
The following descriptive maintenance task sheets are provided in section 10.4.
Management of road killed animals
Management of animal-vehicle collisions (AVC) data
