River landscape without river: The stony steppe of La Crau, Provence - Alpes - Côte d‘Azur
a river is the stony plain of the Crau near Arles in Southern France. Here, the river Durance has, over the course of tens of thousands of years, deposited material from the Alps in an alluvial fan, eventually blocking its own path to its mouth, so that the Durance now empties westwards into the Rhône. The rough sediments of the Crau provide very poor soil conditions for agricultural use, which has therefore been limited to extensive pasturing for many centuries. Nowadays, the Crau has become a refuge for many animals and plants adapted to aridity.
Flora and fauna Not all material carried downstream by the waters is dead; it also includes germinable seeds of Alpine plants as well as the branches of trees and shrubs that can take root in river bank sediments. Such ‘dealpine’ populations can inhabit locations in lower altitudes, where their chances for permanent survival under normal conditions of competition without supply from upstream reaches would be limited. Many fish species in the Alpine region spawn in the rivers‘ upper reaches. Adult fish travel upstream to deposit their eggs;
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larvae and juvenile fish return to the lower reaches with the flow. The largest fish species of the Alpine region, the Danube salmon (Hucho hucho), relies on an intact river network. The total stock of this endangered species can only survive in the long-term as long as they are offered sufficient migratory opportunities among the streams and rivers of the Alps and their foothills. The examples listed here demonstrate that it is not possible to clearly delineate where a river can be defined as an Alpine river and where not. Each of these aspects rests on different spheres of influence, which are furthermore subject to a variety of definitions based on the respective discipline.
Definition within this book All of the above demonstrates that the term ‘Alpine river’ cannot so easily be given a universal definition. The two different approaches – ‘rivers in the Alps’ or ‘rivers from the Alps’ – each have their challenges. This book nevertheless needs firm ground. The editors have therefore decided to use the boundaries of the Alpine Convention as their point of reference for most map depictions, balances, etc. This decision was a