The Danube is one of the most important areas in Europe for biodiversity, yet its wildlife is increasingly coming into conflict with human interest. In this article, I will explore some environmental issues relating to the Danube and what is being done to protect it.
Dikerogammarus villosus is an invertebrate which is colonising large areas of the Danube. It is better known as the ‘killer shrimp’ or ‘freshwater jaws’, for its propensity to eat anything up to the size of a small fish. It is normally found in the Caspian sea area, but has made its way up the Danube, most likely hiding in the ballast of ships. It is one of the many non-native species to colonise the Danube. Though species moving from one place to another is a natural occurrence, the sudden rise in non-native species is having a severe effect on Danubian biodiversity. In some places surveyed, they accounted for 100% of species recorded. It is difficult to provide any simple solutions to the problem; the process of physically removing species requires a lot of work and would disturb native species. It is thought that the success of non-natives has been down to other issues of environmental degradation, such as pollution and climate change, which have weakened native species, opening up ecological niches, which invasives quickly colonise. This implies that non-native species are more of a symptom than a problem in themselves, and the best way forward is to restore the Danube ecosystem to allow native species to flourish.
There are 28 dams on the Danube, with more coming in the future. These have many detrimental effects to the river ecosystem. To start with, they block fish migration. For many species, such as Sturgeon and Danube salmon, migration up and down the river is a key part of their life cycle. Both of these species migrate upriver, to clear shallow waters to spawn (release eggs and sperm into the water). Juveniles will spend their first year in shallow waters before moving to the main body of the river. This is made nearly impossible by dams. Another issue with dams is that the turbines from which electricity is generated can kill fish who try to swim through them. Also they prevent the natural flow of silt and debris down the river making regeneration of the river banks less successful. Many dams are no longer required or working to their full capacity. It is thought that removing these dams is by far the most effective way to restore the river ecosystem. Where the dams cannot be removed, other measures, such as digging channels around the dams and creating ‘fish locks’ to be opened during migration season have been proposed.
The ecosystem provided by the river does not end at its banks. The floodplains that it provides are a hugely important habitat, and are home to many endangered species, such as White and Dalmation pelicans. However, over 80% of the Danube is regulated for flood protection, resulting in ecological degradation of the floodplains. This is a difficult issue to address, as it appears that the human desire not to be flooded is in direct conflict with the ecosytems need for regular flooding. It seems unlikely that any amount of environmental campaigning will move all major cites fifty miles away from the river. However, it is important to note that some measures to reduce flooding may in fact increase the risk. To reduce the risk of flooding in a particular area, one must slow the flow of water upstream, and speed up the flow downstream. But doing this then increases the risk of flooding downstream (as the speed of the flow has been increased). Therefore, by allowing the river to naturally flood in more areas, the flow is slowed down, reducing the risk of flooding downstream. It is hoped that a solution of this kind will be beneficial to both humans and nature.
Many of the floodplains have been drained to make way for farming. In the Danube area, this has happened for hundreds of years, but recently, due to large scale farming and modern methods, it is having a much greater impact on the ecosystem. One of the major sources of pollution in the Danube is run off from agriculture, either effluent from pig farms, or fertilizers and pesticides from crops. These find their way into the waterway and severely affect the ecosystem. Fertilizers and pig effluent contain high levels of nitrates, which help plants grow. However, in large quantities in rivers they cause high levels of plant and algal growth, which smothers out other forms of life. Some solutions that have been proposed include ensuring proper storage of manure and chemicals and a promotion of organic farming along the river.
With all of these issues (and many more not discussed here), it is reassuring to know that something is being done to improve the river quality. In 1994, the Danube River Protection Convention was signed by eleven Danubian states. Since then, other countries have signed, including Serbia. The main aim of this was to ensure that the waters were used in an environmentally sustainable way. In 1998, the International Commission for the Protection of the Danube River (ICPDR) was formed. The ICPDR is an international body which was tasked with implementing actions to meet the EU water framework directive in the region. Though it is far from perfect, it is hoped that the ICPDR will provide a model of international environmental cooperation that can replicated around the world.