Estimating human pressures at the Bothnian Bay

The marine environment of the Baltic Sea is fragile and vulnerable due to its unique location and structure. 85 million people live on its catchment area and 15 million of them live within 10 km from the shoreline. Therefore this has an effect on the marine environment both below and above the sea surface.

Even though the most severe pressures in the Baltic Sea come from eutrophication, the Northern part of the Bothnian Bay struggles with slightly different problems. The discharge from large rivers and limited water exchange creates demanding environment both for marine and freshwater species. For example the aquatic mosses inhabiting the otherwise bare reefs create habitats unlike any other in the Baltic Sea.

In addition to the pressures from the catchment area, the sensitive habitats of the SEAmBOTH project area, such as reefs and sandy bottoms, are affected by several human activities occurring at sea. The increasing marine traffic, construction of offshore wind farms, maintenance dredging of shipping routes and harbours, the deposition of the dredged material and constructed shoreline all effect the physical structure of the sea bed and habitats. These activities cause e.g. physical loss of habitats by destroying the sea bottom or by disturbing the physiochemical environment maintaining the habitats. Usually a single human activity at sea does not cause only one pressure but effects the marine environment through several pathways.

A map of northern Bothnian Bay, showing natura2000 areas, harbours, industrial sites, dredging deposit and navigation line.
Natura2000 -areas and different human pressures in the northern Bothnian Bay on the Finnish side. Map by Jaakko Haapamäki, Metsähallitus.

So – what we do to estimate these anthropogenic pressures? We work with spatial data of human activities and algorithms to estimate the extent and intensity of the pressures. It contains several hours of working on the computer and researching the phenomena in theory. By knowing where the human activities take place, we can estimate the pressures affecting the marine environment. It includes estimation of the buffer zones and attenuation rates from the activities as well as methods to combine several activities together. To better understand and define areas most affected by human pressures, it is essential to combine the varying effects of different activities. When we overlap these pressure data sets with knowledge on the sensitive habitats and species, we can get a clue on the stress caused on the marine environment.

Written by Leena Laamanen, Finnish Environment Institute (SYKE)


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