Kokemäenjoki River Delta, Western Finland - Natural Treasury in an Exceptionally Rapidly Changing Aquatic Environment

Abstract

The catchment of the River Kokemäenjoki covers ca. 27 100 square kilometers in western Finland, and the the length of the river is ca 120 km. The river discharges into the Bothnian Bay, the northern section of the Baltic Sea. The delta is changing and prograding towards the sea exceptionally rapidly. The pace of the growth of the deltaic formations,a s well as the major zones of the macrophytivc vegetation is nowadays some 30–40 meters a year. This makes the delta the most rapidly changing aquatic and littoral ecosystem in the Northern Europe. The Kokemäenjoki River delta is often characterized as a biological hotspot, and major sections of the estuary are included in several leading international nature conservation programmes, i.e. The Natura 2000 network of the European Union, the intergovernmental The Ramsar Convention on Wetlands, as well as in the IBA, Important Bird Area programme established by the BildLife International organization. The diversities of both flora and fauna are very high – at least as regards of the northern location of the estuary. In the Kokemäenjoki River ca. 420 taxa of flowering plants (Spermatophyta) are permanently found (i.e. about a third of the ca. 1 200 flowering plants permanently growing in Finland). Of the pteridophytes (Pteridophyta), there are 17 out of the 57 species of the Finnish taxa growing at the delta. Of the stoneworts (Chrarophyta) the delta is home of 9 species of the 21 taxa found in Finland. The number of bird species breeding in the area is ca. 110, and the total number of bird taxa living and resting during the migration periods amounts to 220 species (i.e. nearly the whole range of the 248 bird species of the permanent Finnish bird taxa). Of the invertebrates, the species composition of dragonflies (Odonata) is best known. There are 25 species of the 55 dragonfly taxa found in Finland. Of the plant species occupying the delta, 5 species of flowering plants and one species of stoneworts are classified as endangered, fulfilling the red list criteria established by the International Union for Conservation of Nature (IUCN). Of the bird species of the estuary, 31 species are included in the Red List of endangered species. The present paper summarizes the data presented in various reports, mainly in Finnish, and majority of them in hardly accessible depositories.