Swedish TV showed a thought-provoking documentary last week about the state of the Baltic Sea. Take-home message #1 was that increasing pollution and uncontrolled emissions/leakage from animal farming, especially in east European countries has and will have large consequences for the Baltic Sea. Take-home message #2 was that it is our increased meat consumption that leads to the establishment of more, and more intensive animal farm-factories, which will produce cheap meat, and which, through uncontrolled emissions will increase the oxygen deficiency in the Baltic Sea. In this respect it is also interesting to note, that one can feed ten persons with the food/area that is required to feed one cow. Eating less meat and more vegetables could thus be an excellent first step to rescuing the Baltic Sea! But what about all the fertilizers that are commonly used to grow vegetables and which would inevitably also end up in the Baltic?
The Baltic Sea is the world’s largest brackish water body with an area of 420 000 square kilometres. The Baltic Sea has a very long geological history, but of this long history we only know in greater detail what has happened during the last c. 15 000 years. Here is a very simplified version of this complicated and fascinating history, which involves ice sheets, melting water, land uplift, damming, sudden drainages, sediments, flooding, and much more. The geologists who have reconstructed this complicated history are real Baltic Sea detectives.
Initially the Baltic Sea was a large, up-dammed ice lake, which was fed by melting water from the large ice sheet. 11 700 years ago this ice lake was suddenly drained, and 7000-8000 cubic kilometres of water flooded across the low-lying area in south-central Sweden towards the west into the Atlantic Ocean. Following this event, a short-lived brackish phase started. Continued land uplift then gradually closed the passages to the west, and the Baltic saw a new freshwater phase, with no connections to the Atlantic. Only about 9800 years ago, although this seems as a very long time, did the Baltic Sea approach its present form, with its connection to the ocean through the Danish Straits. The sediments that deposited during these past 9800 years, testify for several periods during which anoxia, i.e. oxygen deficiency occurred. These intervals with oxygen-poor bottom water conditions seem to have been caused by warmer climatic conditions and less precipitation. However, by looking more closely at the past 150-200 years, it becomes also clear that a connection exists between intensified land use and consequently higher nutrient fluxes on one side, and oxygen deficiency in the Baltic Sea’s bottom waters, on the other side. The geological history of the Baltic Sea can thus teach us quite much about the natural state of the Baltic and the underlying reasons for oxygen deficiency in the past, and can provide baselines for future planning.
With more than 85 million people living now in the drainage area of the Baltic Sea, it is easy to imagine that an even more intensified, industrial agriculture, will lead to inevitable consequences.
You can also read much more about the The late Quaternary development of the Baltic Sea by Svante Björck from Lund University. Geological research into the history of the Baltic Sea is conducted at Stockholm University and at Lund University.