Creatures from outside the Rhineland end up in the Rhine via canals linking the river to other catchment areas and via shipping. These are called exotic species. The species found in the Rhine are mainly fish and invertebrates like mussels. Some creatures travel by ship from places very far away, like Asia or America.

Sometimes this is nice, and often it is special, but it is not always desirable. This is because the new species can change the ecosystem. And sometimes we don’t want that to happen.

An ecosystem is the entire set of plants and animals in a particular environment. Everything in the environment that contributes to maintaining the ecosystem is part of it, such as the soil, water and air. In an ecosystem everything is connected and so the system is balanced.

For example, predatory animals live in the ecosystem and there are enough smaller animals for the predatory animals to eat.

If new species enters an ecosystem this can upset the balance.

Sometimes we do not want that to happen, and then we try to keep the exotic species out of the ecosystem.

But we do not always intervene, because it is all part of nature, and nature itself finds solutions. The ecosystem seeks a new balance.

For example, four exotic species of goby (a type of fish) have ended up in the Rhine. Most of them probably arrived from the Danube area on ships travelling along the Rhine-Main-Danube canal. Their numbers have increased dramatically. One in every five fish caught in the Rhine is a goby. In some places this figure is as high as nine in ten.

Gobies can attach themselves firmly to rocks, helping them resist the swell and waves caused by shipping. This means that they are not so easily washed away and can thrive in the Rhine.

Gobies have positive and negative effects on animals that are native to the Rhine, i.e. that were already living there. They also affect other exotic species, and even members of their own species.

For example, fewer ruffes (a type of fish) are found in areas where gobies are common.
Gobies eat a lot of exotic molluscs such as zebra mussels and clams, as well as the eggs of (sometimes rare) fish. Gobies themselves are a new food source for species such as pike perch, barbel, asp and river perch.

The distribution of species in the ecosystem is therefore constantly shifting.

The spread of exotic species is sometimes a problem, but at the same time it is important for animals and plants to be able to move and spread. This is why countries in the Rhineland are working together to develop nature networks or “biotope networks”.

A biotope is literally a habitat. It is a word used to describe a place or small area with certain characteristics, such as heathland, swamp forest or grassland.

These areas must be connected naturally so that animals and plants can move around and spread.
Creatures that have almost died out or are having difficulty surviving in one area can go somewhere else where conditions are better.

For example, when the climate changes and animals can therefore no longer survive, they would like to move to places where they feel more at home. They are less vulnerable if they can move easily.

Read more about international cooperation.