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 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. Conditions established by transport 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 best practice are listed below.
- Verges and medians play a basic role in road safety, which is always the priority factor. Benefits to biodiversity can be provided through an appropriate maintenance practice.
- Apply practice adapted to target species requirements at sections located in protected natural areas or others hosting priority habitats and species.
- Define procedures to detect and record threatened fauna and flora during the maintenance tasks.
- Apply early awareness measures to detect and eradicate invasive alien species. Do not introduce any invasive species in green area planting.
- Avoid using pesticides and fertilisers. Apply biological control methods and consider soil replacement where vegetation overgrowth is presenting a potential conflict.
- Avoid creating ‘ecological traps’ where animals are attracted to places where they could become trapped with no possibility of exit, get injured or die.
- Consider providing habitats for small endangered fauna species avoiding attraction to hazardous areas where the risk of mortality may be higher.
Use suitable machinery
- Avoid machinery movement on verges as much as possible to avoid compacting and disrupting the soil.
- Provide mowing machines with digitalized maps indicating the location of sensitive road sections where specific maintenance tasks must be undertaken. GPS- and GIS- equipped mowing robots will improve nature friendly patch maintenance.
- At sensitive sites, use machinery suitable to reduce wildlife mortality or injury.
- Suction mowers are not recommended in sensitive sites and should be restricted to sites where grass could not be removed by other means.
Avoid attracting large animals
- Remove palatable vegetation such as trees and bushes producing large fruit and nutrient-rich grasses which attract deer, and avoid dense shrub vegetation that provide refuges for wild boar.
- Provide a large strip (approx. 3 to 5 m depending on the species, landscape and road speed limit) of poor soil with short grass, which widens the driver’s field of vision and gives them opportunity to adapt their driving behaviour if an animal approaches.
Remove or modify any barrier that could increase wildlife mortality risk
- Replace or adapt any kerbs on roadsides and medians that create a barrier to small animals, stopping them getting off the road and causing an increase of mortality risk. Wildlife experts can advise about adaptation required according to target species.
- In critical road stretches with no perimeter fencing and high numbers of road casualties, consider replacing concrete safety barriers (New Jersey) which create difficulties for large animals to cross, by steel rope safety barriers.
- Modify gullies to avoid mortality of small animals where this has been recorded.
Apply gritting compatible with wildlife biodiversity
- Evaluate the use of calcium magnesium acetate as an alternative to sodium chloride to be applied in sensitive areas with endangered flora species.
- Gritting substances must be applied in a way that they do not spill over to immediately adjacent zone with grass.
- Prevent salty runoff from reaching retention ponds adapted to host wildlife or any other freshwater habitat.
- Prevent deer and other ungulates from accessing roadside salt depots.
The following descriptive maintenance task sheets are provided in Section 7.4 – Maintenance tasks sheets: