Abstract

he Ayse ́n River basin is located in southern Chile (between 45o and 46o S) and covers an area of 11,456 km2 (Figure 1). The western part of the basin contains a series of steep, highly dissected subwatersheds. The Ayse ́n basin is somewhat unusual for Chile in that several of the main tributaries have their origin in the dry plateaus to the east of the main Andes range. Given consistent prevailing winds off the southern Pacific, the spatial distribution of precipitation within the basin is highly heterogeneous. The basin’s patterns of precipitation, soil genesis, vegetation and human management and extraction all affect the nutrient cycles and export. The vegetation of this part of the Chilean Patagonia is characterized by temperate evergreen and deciduous forest dominated by Southern Beech (Nothofagus sp.). Because over 46% of the basin is still forested, the area is often considered one of the most pristine regions of Chile. However, the landscape has been changed significantly by human activities since the end of the 19th century (see also Delgado and Bachmann, this volume). Colonizers to the area brought with them their cattle and cultural valuations of landscape. Spurred on by their government, these settlers cleared pastures through the deliberate setting of fires, resulting in the loss of approximately 60% of the original old-growth forest throughout the region. Cur- rently, the landscape shows a consistent pattern of settlement and modification to the river valleys. This chapter provides a description and analysis of the rugged and fascinating landscape found in the Ayse ́n River basin and how historic changes in the basin are connected to the socio-political context of 20th century Chile. We base our analysis on current geographical data but also environmental and social history using a S-DPSIR framework. Given that stake- holder narratives and scenario evaluations have become a central part of ecological modeling for decision support and management purposes (see Mar ́ın and Delgado, this volume), it is critical to understand historic patterns of change.