Management and construction of road infrastructure habitats for biodiversity

Page not available in Swedish.

Background

Considerable efforts are put into monitoring and management of species-rich road verges (SRV). The SRV denotes a well-developed concept in Sweden (AVK in Swedish terminology), in which certain road sides are designated as SRV based on flora composition, and managed with certain management activities. Monitoring of SRV however points at declining species richness in many areas, in spite of presumably adapted management.

In order to enable proper measures for maintaining and forming of biodiversity-rich road infrastructure habitats (IH) we need better knowledge about the ecology and threats of different SRV in relation to different management methods. With such knowledge we can evaluate the limitations of the present management and suggest changes. 

Activities

This subproject will use field data to analyse which environmental conditions, including management, that constitute ecological key factors for different biodiversity values (e.g. species groups) in road IH. The ongoing management will be regarded a large-scale experiment and evaluated in order to discern effects of different maintenance and construction activities on those key factors. A number of modifications of management and new management methods will be tested as new experiments.

The subproject has two aims: 

  • A) to analyse why some, but not other, road verges have high biodiversity values, and why some have remained species-rich over time while others have become deteriorated.
  • B) to analyse how biodiversity-rich road habitats can be assigned to different habitats in terms of species composition and ecology, and how habitats can be grouped according to their needs for biodiversity management activities. 

Data for both A and B will be derived from Trafikverkets databases on SRV, and from new field surveys, in which we compare:

  • (1) SRV and ordinary road verges (or road verges along a gradient in species richness),
  • (2) SRV that have lost vs.not lost their values over time (10+ years), and
  • (3) SRV that have been subject to different management activities (including activities specifically aiming at biodiversity).

These studies (1-3) can be regarded a use of the ongoing STA activities as a large “living” field experiment. In addition, a number of particularly important management activities will be identified early in the subproject and tested in specific experiments throughout the project period. Vegetation data will be sampled, but in order to obtain results faster than the slow vegetation responses can provide, we will also study some indicator species in a life-cycle perspective. Some SRV habitats are important for different insect groups, for example bees, weevils, and leaf beetles. Data on some insects of conservation concern will be collected during the field surveys, together with data on their habitats (in Swedish livsmiljö), such as host plants, nesting sites, and pollen/nectar resources. 

Data will be analysed in order to identify which environmental variables that constitute ecological key factors for different biodiversity-rich IH. Examples of environmental variables are management practices (current and previous), soil, slope, sun exposure, succession, surrounding species pool, and occurrence of invasive species.

We will use both quantitative and qualitative approaches, using, for example, species-habitat models developed at Swedish Biodiversity Centre. Habitat identification and grouping will be done using structured models based on a combination of functional species groups, ecological values, ecological processes (including management), and basic conditions. 

The results will be published scientifically.

Output

  • Knowledge about which environmental variables that account for SRV, and for the variety of SRV (ecological key factors).
  • Knowledge about how such ecological key factors can be obtained by management activities.
  • Knowledge about how different types of SRV can be identified in the field, and of which packages of management activities that are required for different groups of SRV.

In total, this output will provide a necessary, but today largely lacking, knowledge base and cost-efficient toolbox for planning, prioritizing, performance, and monitoring, to be used in activities for maintenance and construction of IH.

The results will significantly help in halting the loss of SRV at the landscape level, both through the preservation of existing SRV, and through better use of the potentials for creating SRV at road construction and rebuilding. From a theoretical perspective, the results will considerably enhance the knowledge of the ecology of IH and their species.

Study areas

The subproject will be performed in two larger geographic areas and four smaller areas with special values and ecological conditions. The larger areas are south-western Sweden (Trafikverkets region Väst, having 22 management areas; DO:s) and eastern Sweden (including some DO:s in Trafikverkets region Öst and some in region Stockholm). The smaller areas are DO Öland (region Syd), and limestone-rich areas in DO Rättvik, DO Krokom, and DO Sveg (all in region Mitt).

All study areas are rich in known SRV of several types, such as limestone types and sand types, occurring in both agricultural and forest landscapes. In both areas, IH are important for a number of red-listed species and other species of conservation concern. Several DO:s in both areas provide a potential for comparing SRV that have lost their values with those that have not, and to link differences to management activities and other environmental conditions.

A large number of SRV will be evaluated using both Trafikverkets own data and new field data, in order to identify ecological key factors for habitat quality in different types of SRV. 

There is also a great potential for evaluating biodiversity effects of different recent and ongoing construction and rebuilding activities. On initiative of Trafikverkets ecologists, some biodiversity inventories have been performed in connection with construction, re-building, and maintenance, and there have also been some experimental establishment of new vegetation. Such sites provide an opportunity for evaluating effects of specific biodiversity-related management activities over time. Initially in the project, potential study sites with such activities will be searched for, be evaluated and the most suitable ones be chosen. For example, we will pay special attention to the following, promising sites:

  • Skövde. New road stretches with large slopes (and adjacent stretches that have not been rebuilt). Experimental sowing of species-rich vegetation, and transplantation of particular species, are initiated.
  • The Kattarp area, Halland. New road (national road 15) since 10-15 yrs. Bare sand and thin re-spread top soil in north and south facing slopes. Experimental sowing on different substrates initiated, with some vegetation data.
  • Mellbystrand. Large area mown with agricultural equipment. May be suitable for experiments on mowing techniques and measures for vegetation succession.
  • The transversal main roads on Öland. Some parts have been rebuilt, and it is also possible to study effects of top soil removal.
  • The Åminnen area, Dalsland. Experiments have been performed with leaving islands of vegetation at top soil removal.
  • Långeskogen, Filipstad. A coming case of how to move and favour red-listed species (Gentianella) when rebuilding.
  • Glimminge, Uddevalla. Various measures for improving species-richness of road slopes: seeding, planting, removal of nutrient rich soil, and root pulling of shrubs.
  • Roasjö, Borås. Various measures for preserving SRV when rebuilding.
  • Osdal, Borås. Road through a sandy area at an old military training field; hotspot for plants and wild bees. Some measures for creating sand habitats have been performed, some areas are still to be vegetated.
  • Road Uppsala-Östhammar. Rebuilt and new road (recent and ongoing), through a mosaic of soil and landscape types (of which sandy types and lime-rich types are particularly interesting), and adjacent to known SRV. 
  • Motorway E4 North of Uppsala, following the Uppsala esker. Large sandy slopes and several more recent soil disturbances, adjacent to areas with species-rich vegetation and high values for sand insects.
  • Stingtorpet-Tärnsjö, Heby. Ongoing experiments with vegetation establishment, including re-spreading of top soil.
  • Söderön, Östhammar. Surveys of host plants for red-listed insects have been performed, which can be linked to timing of mowing.
  • Funäsdalen-Fjällnäs. Surveys of sub-alpine meadow plants have been performed, which can be linked to timing of mowing.

In DO Norra Roslagen (region Stockholm), there is detailed information on biodiversity in grasslands in the surrounding landscape, which can be compared with IH in later landscape analyses.

Photo: Jörgen Wissman