SR17 How does removal of vegetation affect roadside vascular plants and invertebrates?
Many species that previously associated with meadows and pastures now thrive on roadsides. For reasons of traffic safety, vegetation is regularly removed from most roadsides. But how should this kind of management be carried out in order to benefit biodiversity as well?
Roadsides as substitutes for meadows and pastures
As agriculture has been modernised, the area of semi-natural grasslands has fallen very sharply in Sweden. Today only fragments of such grasslands remain in the farmed landscape. In contrast, roadside habitats have increased in area. The Swedish Board of Agriculture recently estimated that a total of 164,000 hectares of managed grasslands occur on roadsides in Sweden. This is close to the total amount of semi-natural pastures, meadows and similar grasslands in Sweden (ca. 250,000 hectares).
Roadsides are usually mowed every year for traffic safety reasons, and sometimes plant litter is removed to favour more demanding plant species. In some cases, vegetation along roadsides is controlled by grazing or burning instead. This means that there are similarities between roadside maintenance and management of meadows and pastures, and many species that were previously mainly associated with semi-natural grasslands of the latter kinds now thrive along the roads instead. For example, almost 300 animal and plant species included in the Swedish Red List of threatened species are found in roadside habitats.
Recommendations for roadside management to promote conservation values are mainly based on botanical studies in meadows, pastures and similar open grasslands. However, key stakeholders have emphasised the need for more targeted management recommendations based on actual roadside studies. Due to the use of road salt for de-icing, ditching and reinforcement activities, sowing of exotic plant material and other measures particular to the maintenance of roads and roadsides, plants are not likely to respond to management in the same way there as in other grasslands.
Mowing, grazing, burning and selective mechanical removal of plants
EviEM has recently finalised a systematic map of the evidence on how different kinds of roadside management affect biodiversity (see review SR9). We identified about 300 studies of this topic. Many of them are highly relevant to environmental conservation, not least a number of studies of how vascular plants and invertebrates along roadsides are affected by mowing, grazing, burning and selective mechanical removal of plants. Since all of these techniques are based on removal of biomass, they are in a sense comparable.
EviEM now proceeds with a full systematic review of what the latter studies have found. Members of the review team that produced the SR9 systematic map will also conduct the review of roadside vegetation removal. The team is chaired by Regina Lindborg, professor of physical geography at Stockholm University, and Claes Bernes, EviEM, acts as a project manager.
A number of stakeholders were asked for advice on how the review should be performed. Helped by their comments, the review team compiled a protocol (a detailed plan for the review, specifying the questions to be answered, how and where searches for data will take place, criteria for inclusion or exclusion of studies, and much more besides). The protocol was published in the scientific journal Environmental Evidence on June 15, 2017 (see link at right).
Regina Lindborg (chair), Dept. of Physical Geography, Stockholm University, Sweden
James M. Bullock, Centre for Ecology & Hydrology, Wallingford, UK
Kris Verheyen, Dept. of Forest and Water Management, Ghent University, Belgium
Simon Jakobsson (project assistant), Dept. of Physical Geography, Stockholm University, Sweden
Claes Bernes (project manager), EviEM, Stockholm, Sweden