E15: Landscape Fragmentation

An increasing number of man-made obstacles splits up the landscape, reducing the effective mesh size and impacting biodiversity in a progressively negative manner.

The Landscape Fragmentation indicator records the degree to which Switzerland’s landscape below 2,100 meters above sea level is cut up by artificial barriers such as roads or settlements. As more and more such barriers split up the landscape, animals are increasingly prevented from moving about freely, which in turn keeps adding to the pressure exerted on biodiversity.

Development in Switzerland

Landscape fragmentation is measured by effective mesh size, i.e. the size of patches remaining free of barriers cutting up the landscape. The greater the number of barriers cutting up a landscape, the smaller the effective mesh size. In the past 70 years, the effective mesh size has been steadily decreasing, as Switzerland’s landscape underwent major fragmentation processes during that period of time.

Effektive Maschenweite in Quadratkilometer
  1935 1960 1980 2001 2007
Switzerland 383 341 291 285 283

 

Interpretation example

The effective mesh size in Switzerland has been narrowed down from 383 square kilometers in 1935 to 283 square kilometers in 2007. Please note that the last observation interval is considerably shorter than all that precede it.

Comments

  • Effective mesh sizes refer to Switzerland’s landscape below 2,100 meters above sea level, excluding waterbodies.
  • Data are available for 1935, 1960, 1980, 2001 and 2007, the years when completely revised National Maps of Switzerland were published. 2001 and 2007 datasets were created using original digital data (VECTOR25), while existing National Maps (1:100,000) as well as the Dufour Map were digitalized in order to obtain the necessary information for 1935, 1960 and 1980.
  • In computing effective mesh size, national borders were considered to be actual barriers, while regional boundaries were not taken into account.
  • Sections of roads and railroad tracks may be reclassified for political or methodological reasons, which impacts effective mesh size.
  • Directional lanes of highways count as two individual roads.
  • As a measuring unit, effective mesh size assigns equal weight to all barriers. In real life, however, it makes a big difference whether an animal is confronted with a small country road or a highway. While it is possible that for some species, all listed infrastructure elements might constitute insurmountable obstacles, for most species, it will be the nature of the barrier placed in their path (volume of traffic, wideness, animal-tight fences, etc.) that carries the most weight.
  • Switzerland's villages, agricultural areas and forests are rendered accessible by a multitude of small roads. Taking them into account would reduce the country's effective mesh size by two thirds—or even nine tenths on the Central Plateau<cite>1</cite>. However, small country and forest roads were disregarded in computing effective mesh size for the purposes of the E15 indicator.
  • The issue of landscape fragmentation has been on the agenda of Swiss authorities for a while. Back in 1998, a joint publication by the Federal Offices for the Environment and for Spatial Development titled Landschaftskonzept Schweiz (“Swiss Landscape Concept”)<cite>2</cite> requires the sprawling of settlements to be contained and the fragmentation of landscapes by new and existing roads or railroad tracks to be minimized (material objectives 8c and 10d).

1 Environmental Watch Network Switzerland (NUS), evaluation protocol for parameter 9a (unpublished working paper, not available in English)

2 Federal Office for the Environment, Federal Office for Spatial Development (ed.), 1998: Landschaftskonzept Schweiz. ARE-Reihe Konzepte und Sachpläne. Bern, Federal Office for the Environment, Federal Office for Spatial Development.175 p. (abstract available in English)

Bedeutung für die Biodiversität

Neue Bauten verkleinern den Lebensraum von wildlebenden Tier- und Pflanzenarten. Auf den Strassen sterben jedes Jahr viele Wirbeltiere und unzählige Insekten. Infrastrukturanlagen wirken sich auch indirekt auf die Landschaft aus, etwa durch Lärm, Licht, Abgase oder Veränderung des Mikroklimas. Die Verkleinerung und Zerschneidung der Lebensräume dezimiert und isoliert bestehende Tierpopulationen, und das Risiko steigt, dass diese lokal verschwinden. Für Tierarten, die am Boden leben, können Strassen unüberwindbar sein, weil sie zu trocken, zu breit, zu stark befahren oder eingezäunt sind. Besonders betroffen sind Tierarten mit grossem Raumbedarf und Arten, die jahreszeitlich wandern.