Wildlife & Traffic

A European Handbook for Identifying Conflicts and Designing Solutions

5 Planning Tools
Original version (2003)
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5.4 Fragmentation impact assessment of the new infrastructure and EIA

The approach should be analytical and include a substantial empirical element and should be performed by experienced ecologists, conservation biologists and landscape specialists.

Basically, the EIA consists of the following phases:

  • Defining the study area.
  • Inventory stage: mapping, field surveys and assessment of natural features.
  • Evaluation of possible conflicts and assessment of risk of fragmentation.
  • Discussion with road designers, planners, architects and environmentalists.
  • Realignment and supplementary investigations.
  • Selection of alternatives to be considered in the EIA process.
  • Planning of mitigation and compensatory measures.

In practice, the EIA is an iterative process, which is more precisely described in Section 5.4.4 and in the Figure 5.1 opposite.

Figure 5.1 - The typical iterative process of an EIA.

5.4.1 Defining the study area

Clearly defining the study area is crucial for a meaningful study of fragmentation issues. In general the study area must be much broader than the corridor within which the project is to be located, and is determined by the existing landscape structures, fragments and features which are sources of fragmentation. In defining the study area, different scales should be considered:

  • National scale: observation of long distance migration routes, local bottlenecks and the connection of isolated populations - even when the target species does not permanently live in the area. 1:250000 may be an appropriate scale.
  • Regional scale: focussing on the impact of the infrastructure, other barriers in the area, topographical connectivity, wooden areas, etc. An important objective is to describe the frequency and location of mitigation measures. 1:50000 may be an appropriate scale.
  • Local scale: detailed studies of the area including populations, habitats and their locations. Useful information includes observations from local specialists, hunters, forestry personnel, etc. An important objective is to describe the exact frequency, location and dimensions of mitigation measures. 1:5-10000 may be an appropriate scale.

The size of the study area varies with the density of built-up areas and the infrastructure network. Normally the more sparsely populated an area, the larger the study area used. Several mapping scales may be used: an overall view of the area is necessary for analysing the fragmentation (e.g. 1:250000 and 1:100000) and smaller scales allow critical areas to be pin-pointed for decision making (maps or aerial photos of 1:25000 or even 1:10000).

Figure 5.2 - Definition of the study area may vary from narrow corridors to whole regions when long distance migration routes are an important consideration. The figure shows an example of a study area expanded to include significant areas of nature conservation. (Danish Road Directorate 2001: VVM Brande-Riis)

Figure 5.3 - The scale of maps is crucial. Different scales may be used in parallel for different purposes. The mapping must be detailed enough to include all relevant information. The above figure shows a Norwegian map of natural features. (Natural environmental value analysis Hw23 Linnes-Dagslet, Norwegian Public Roads Administration 2001)

Figure 5.4 - Example of mapping spatial data. Relevant data should be mapped in a way that supports the iterative process of planning and impact assessment. The use of data layers and significant signs and symbols helps communication between the parties involved. (Danish Road Directorate: VVM Brande-Riis)

5.4.2 Inventory stage

This stage involves a desktop study of planning documents, field inventories and mapping. The features mapped are:

  • Landscape conservation designations, landscape elements, undisturbed landscapes and coastal and landscape protection zones.
  • Legislative framework and regulations: special protected area maps and regulations, zones of special interest for flora or fauna (including dispersal corridors), areas designated by the Habitat Directive and the Birds Directive, forests, etc.
  • Species: stands of rare or endangered plant species, sites of fauna value (e.g. breeding or wintering grounds).

All the layers of spatial information for environmental factors and the infrastructure network should be mapped, preferably using GIS. Mapping should include conflict points with migration routes, possible negative influences on vulnerable areas, fragmentation of valuable habitats, etc.

Figure 5.5 - Example of mapping conflicts in a corridor: landscape, recreation and biology. The graphics used should be chosen to highlight the issue; in this case, the fragmentation of habitats and the recreational landscape by a potential road alignment. (Danish Road Directorate: VVM Billund omfartsvej)

5.4.3 Ecological assessment process

The natural heritage in the study area is evaluated to identify ecological issues. The assessment should be based on the evaluation of:

  • Habitat diversity.
  • Habitat size.
  • Degree of disturbance.
  • Rarity of habitats.
  • Conservation status, for example nature reserves or Natura 2000 sites.
  • Important landscape elements. • Species diversity.
  • The presence of red-list species, protected species and species of the annexes of the Birds and Habitat Directives.
  • Populations of game animals and emblematic species (i.e. species with strong cultural or emotional appeal).
  • The importance and potential for recreational use and related disturbance to wildlife.

Each routing option is shown on a map which illustrates the route's impact and the sensitivity of the area. The illustrations should show:

  • Size of the habitats and their location, including small and isolated biotopes located on either side of the route.
  • Approximate size of populations on either side of the route (small, isolated populations are always vulnerable).
  • Relative location, distribution and spacing of habitat fragments.
  • Existing dispersal and migration corridors, including ecological and landscape connections and resting areas, which are not always natural habitats.
  • Habitat restoration potential.
  • Barrier effect of the infrastructure on small biotopes such as ponds with amphibian populations.
  • Barrier effect of the infrastructure with regard to recreational areas and public access

The maps form the basis for analysing the possible effects of the route and identifying points of conflict between natural features and the suggested alternative alignments.

Figure 5.6 and 5.7 - Computer visualisations showing alternative options for a viaduct crossing the Gudenaa river valley, Denmark. (Danish Road Directorate: VVM Motorvejen Herning-Århus ved Silkeborg)

Efforts must be made to maintain linear structures which connect habitats and populations. Particular attention has to be paid to rivers, streams, riparian forests, wooded corridors and networks of hedges and dikes, which in an intensively used landscape can often be the last refuge for many species. An assessment of the possibilities for crossing the infrastructure must be made: bridges, tunnels, culverts, etc. The density of mitigation measures should be based on vulnerability studies (for more details on density see Section 7.1).

5.4.4 Iterative process of project location and design

An iterative process is ideal if road engineers, planners, architects, conservation biologists, landscape ecologists and cultural heritage specialists have input on project location and design. The multidisciplinary process will lead to changes of routing and alignments, planning of mitigation measures and other types of environmental adaptation. The process around project location and design is illustrated as part of the overall EIA in Figure 5.1. The conclusions of conflict analysis made in the evaluation stage must be presented to the developers and road designers during the next stage of the process.

5.4.5 Consideration of alternatives

The selection and ranking of project alternatives must be based on the following considerations and guidelines (for more detailed descriptions see Chapter 6):

  • Fragmentation should be avoided especially in areas of high conservation priority and in areas that are not fragmented.
  • Functionality of dispersal corridors should be maintained. Relief (hills and valleys) often provides opportunities for decreasing the barrier effects of infrastructure. Rivers, watercourses, riparian forest, hedgerows and rows of trees should be taken into account. 
  • Infrastructure should be placed in development corridors (areas already disturbed by urbanisation, industrialisation, technical facilities and infrastructure) to avoid further fragmentation of undisturbed, pristine landscapes.
  • The conservation of coherent landscape elements such as river valleys, coastlines and ridges. 

Landscape and biological features must be weighed against technical, visual and aesthetic considerations: is the site of high ecological value (for instance part of the Natura 2000 network); could the routing be changed; is recreation or tourism important to the area; would it be possible to pay particular attention to the architectural quality of the passages? Judicious decisions in the planning phase can do away with the need for measures to reduce the impact of the infrastructure later on.

Figure 5.8 - Example of a plan to show alternative routing options and the study area. (Danish Road Directorate: VVM Frederikssundsmotorvej)

5.4.6 Planning the monitoring programme

During the planning phase and the process of choosing appropriate measures, attention should also be given to monitoring and evaluation. Clear objectives for the chosen solutions as well as criteria for their evaluation should be described and implemented in the monitoring programme (see Chapter 9).