Indicator: Landscape dissection | Umweltbundesamt

At a glance

• The data on undissected low-traffic areas are used to describe the fragmentation of the landscape by transport routes.
• In 2015 undissected low-traffic areas accounted for 23.5 % of Germany’s total land area.
• The target of the Federal Government is to retain a proportion of 25.4 %.

Environmental importance

Traffic adversely affects biodiversity by fragmenting habitats and creating noise and air pollution. Humans are affected by the loss of recreational areas. The indicator is based on a threshold area of 100 square kilometres (km²), a size originally defined as a recreational space that allows hikers to go on day excursions largely undisturbed by intrusive sights or sounds.

Low-traffic areas are not necessarily near-natural. In Mecklenburg-Western Pomerania and Brandenburg, for instance, low-traffic areas make up more than 50 % of the total land area. This is largely because these Federal States are sparsely populated and have a lower density of transportation networks and less traffic, especially on regional and local roads. Furthermore, these regions are mainly characterised by intensive agriculture.

Assessing the development

In 2015 undissected low-traffic areas with a minimum size of 100 km² accounted for 23.5 % of the total German land area. In the previous 2010 survey, the figure was 23.2 %. A slight increase in the areas of the undissected low-traffic is thus recorded for 2015. The results, however, show a certain spatial dynamic within the individual federal states.

In the National Strategy on Biological Diversity, the Federal Government has set itself the target of keeping landscape fragmentation at least at a constant level (BMU 2007). The level of fragmentation in 2005 has been chosen as the target (25.4 %). In 2000 this figure was at 26,5 %. However, the basis for calculation (traffic density counts) was incomplete in 2000 and 2005. Models were therefore used to calculate traffic loads across the entire road network for the year 2010. Closer analysis shows that the indicator value is significantly influenced by traffic loads on the subsidiary road network, i.e. the volume of traffic outside the main transport routes. Thus, the indicator is subject to certain fluctuations, depending on the chosen calculation method. This point must be considered when assessing the target attainment.

Methodology

The indicator is calculated by determining the proportion of Germany's total land area which is not dissected by transport routes. Dissecting transport routes are defined as roads (motorways, national, regional and local roads) with a traffic density of 1.000 vehicles per day or above, at least double-track or electrified single-track railway lines and canals with the status of ‘federal waterway’ (Category IV or above). These areas can be identified using geo-information systems. Modelling and traffic counts (to calibrate the model) are needed to fully determine road traffic densities. The modelling approach for 2010 is described in Bosch & Partner et al. 2013, for 2015 in SSP Consult Beratende Ingenieure GmbH 2018.

The scheduled counts for the summer of 2020 could not take place due to the Covid-19 pandemic. Since spring 2021, the relevant traffic volume counts are now being conducted. This will be followed by further modeling and calculation steps.

References:

Bosch & Partner et al. 2013: Bosch & Partner GmbH; University of Kassel; TCI Röhling. Ökologische Risikoeinschätzung auf Bundesebene (final report to the F+E-project 3510 82 3100 on behalf of the Federal Agency for Nature Conservation (BfN); unpublished, can be requested at BfN, in German only).

SSP Consult Beratende Ingenieure GmbH 2018: Erstellung eines bundesweiten Straßennetzes mit modelltechnisch ermittelten Verkehrsbelastungen unter Verwendung der Straßenverkehrszählungen (SVZ) 2015 als Kalibrierungsgrundlage (Expert report commissioned by the Federal Agency for Nature Conservation, in German only).