The merging of human activity and natural change: temporal and spatial scales of ecological change in the Kokemaenjoki river delta, SW Finland

Human cultures have had important influences and major impacts on nature and its natural state along rivers. Riversides have been settled for thousands of years and human interpenetration of nature along rivers is multilevel both in time and space. In this descriptive article, we discuss how human activities have changed in the Kokemaenjoki river delta in the northern Baltic, SW Finland and how these altered activities have influenced the formation structure and ecological dynamics of the delta. Vegetational changes during the last 100 years are used as a proxy of environmental change. We study the complicated human culture-nature interpenetration at different temporal and spatial scales. The Kokemaenjoki river delta was formed during deglaciation after the last Ice Age. Because of rapid land uplift (about 0.7 cm per year) and the fluvial load transported by the river, the delta is moving towards the sea at a quick pace. Livestock farming has kept meadows open and shaped their vegetation for thousands of years, and field clearing has had significant impacts on the delta since the 16th century. Further, disturbances such as damming or the establishment of factories along rivers have also shaped the Kokemaenjoki river delta for centuries, changing the river's role in transporting organisms and debris. Remarkably, structural changes associated with agricultural land use in the late 19th and in the middle of 20th century and damming for hydropower purposes in the 1920s and 1940s, seem to have had only a minor influence regarding the vegetation dynamics in this wetland habitat. It seems that the delta can retain its conservation value in the future. Land uplift ensures that new wetland habitats are constantly created. Since the delta has experienced human impact from the very beginning of its formation, it appears that the occurring vegetation has adapted to those influences and the interrelation of human presence. (C) 2002 Elsevier Science B.V. All rights reserved.