La trajectoire paysagère d’un bassin versant bocager normand depuis deux siècles : enjeux méthodologiques pour une étude géohistorique

Abstract

The bocage landscape of north-western France has undergone major changes since the middle of the twentieth century, its structure having been altered by land consolidation, the rationalization and enlargement of plots, and the levelling of hedgerows. The environmental consequences of these landscape changes are significant: water erosion, pollution of aquatic environments and loss of biodiversity. The aim of this article is to study the evolution of an agricultural area that is representative of the changes that have affected bocage landscapes over the last two centuries. Using the example of a small, historically bocage watershed in Calvados (Le Tortillon), the methodology is based on a geohistorical approach, combining the use of archives, particularly land registry records, and aerial images within a Geographic Information System (GIS). Although land registers provide precise information on land use in 19th-century landscapes, the article questions the relevance of their representation in terms of landscape structure. The results of two centuries of landscape trajectory show the evolution of land use and bocage structure. In particular, there has been a steady decline in the number of hedgerow lines since the 1940s, in line with the opening up of the landscape, land consolidation and the meteoric increase in the size of agricultural plots. The results of these centuries of change shed new light on the trajectory of a bocage landscape over the last two centuries, and help us to understand the landscape of tomorrow.

Keywords

• GIS
• landscape
• agriculture
• landscape changes
• geohistory
• landscape dynamics