Landscape ecology of the Dutch coast

Abstract

This paper is a summary and elaboration of an earlier publication in Dutch on the compilation of a landscape-ecological map, scale 1 : 50 000, of the Dutch coast. It is argued that such an integrated map is the best basis for the conservation and management of the coastal dunes and salt marshes. It may be combined with local more detailed vegetation maps, some examples of which are mentioned in the context of management.

The Dutch North Sea coast is a ca. 350 km long chain of sandy beaches and sand dunes, from only 100 m to more than 10 km wide. On sheltered stretches of dune coasts along estuaries in the Southwest and on the Wadden Sea islands, salt marshes have developed. The small-scale gradient structure of the beach-dune-salt marsh complex is emphasized.

Since 1955, a classification of landscape types has been developed for this area, which is mainly based on vegetation, geomorphology, soil types and history of human use of the area. Local maps were prepared in the field, based on topographical maps, scale 1 : 25000, most of which were updated with the help of recent and more detailed maps, based on aerial photographs, scale 1 : 2500 – 1 : 10 000, combined with new field work. In the general report (Doing 1988), the main results are presented, including a map redrawn on the scale 1 : 50000.

The main principles of the landscape typology and mapping were:

• 1. A ‘landscape’ is defined as an area of land (and water), which can be recognized as an integrated structure, and distinguished from neighbouring units, both in the field and on aerial photographs. It can be described in terms of vegetation, geomorphology, soil and land use, where the relative importance of these aspects for landscape classification may be different in different regions and zones.

• 2. In sand dunes and salt marshes, there is usually a finegrained, complicated pattern of ecosystems (units of vegetation which are functionally related to their environment). Such patterns can only be mapped on large scales (1 : 2500). Therefore, a landscape unit must be conceived as a complex of ecosystems. Consequently, various stages of succession may be included in one and the same mapping unit, especially in old dunes.

• 3. The repetition of certain patterns of ecosystems, showing functional and historical coherence, provides the geographical basis for the mapping units. Boundaries are usually determined by geomorphological aspects, which are related to geological, climatological, vegetation and land use history.

• 4. The units are identified with the help of a flexible system of letter and number symbols. There are 15 ‘main landscape types’ (nine for sand dunes, six for salt marshes) and 16 ‘auxiliary types’, some of which occurring in both dunes and salt marshes. Most units are combinations of these types; they are indicated by at least two letters, in a sequence adapted to the local situation. In this way, a ‘landscape language’ was developed, which needs some effort to understand, but proves to be an effective tool to describe a very complex situation.

Finally, some examples are given of the use of this landscape-ecological approach to problems and perspectives of the conservation and management of coastal landscapes.