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Invasive introduced species

Invasive introduced species

water hyacinth invasive in many countries

Water hyacinth is invasive in many countries

Non-native invasive plants

Many non-native species of plant exist within the confines of gardens or agricultural holdings. However, some species adapt well to their new surroundings and become too successful, covering wetlands and waterways to the extent that they push native species out, block channels and cause de-oxygenation when they die off and decompose.

Waterways are particularly vulnerable because they distribute plants, and act as networks along which they spread. Water Hyacinth, see right, has spread from its native South America to become an invasive plant in most other continents. It is causing major issues in Lake Victoria, for example, blocking navigation, water pumps, fisheries and even acting as a breeding ground for disease.


The Global Invasive Species Programme offers an international platform for information on both plant and animal species. The Global Invasive Species Database allows you to search for specific species. It has both background reports as well as resources to help tackle invasives. The DAISIE project is a European invasive species programme, working to support joint approaches to tackling invasive plant and animal species.

Check New Zealand’s weedbusters website, which gives practical ideas about dealing with invasive weeds through local projects. NIWA has information on dealing with invasive species across a range of types, including strategies for addressing the problem and resources to help develop solutions. SPREP have also developed an invasives fact sheet which gives general information.

Creston Valley have major issues around yellow flag iris, introduced from Europe and now becoming invasive in their reserve. In the Camel Valley, Cornwall, UK, work is taking place to remove invasive plants along the river. The UK living river project shows how you can work with local communities to raise awareness of invasive species, and get involved in restoring small rivers.

Zebra mussels

Zebra mussels

Non-native animals

Of course, we also suffer from the introduction of non-native animal species, which present their own problems. Species such as the zebra mussel (Dreissena polymorpha), originally from south east Russia, is now widespread in Europe and North America. Producing up to a million eggs per year, it is not hard to see how it spreads prolifically.

Other wetland animals include mammals such as the American mink in Europe, fish such as the carp, and birds such as the Canada goose. Controlling these species, which are often highly mobile, can be both expensive and present additional issues around animal welfare. For some information on dealing with non-native animals, check WildCRU (Oxford UK) who are doing a lot of work on the issue.

The WLI network is endorsed by the Ramsar Convention on wetlands and coordinated by WWT.


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