Invasive species taking over - Tens of millions

Tens of millions

There are no definitive industry wide figures for just how much the Japanese Knotweed plant costs to eradicate. But even on relatively small building sites the cost of control can run into hundreds of thousands of pounds. Developers are also often required to tackle the plant in order to maintain their legal obligations under the Wildlife and Countryside Act 1981. The annual cost across Britain is likely to be many tens of millions. The cost to eradicate Japanese Knotweed in Britain using conventional methods was estimated a couple of years ago to be £1.56 billion.

But there are other invasive species in our waterways. The American Mink was brought to Great Britain in the early 20th century for fur farming. Then they became established in the wild after escapes and deliberate releases. They are opportunistic predators and will take a wide variety of prey, often killing more than they require for food. Among their prey is the native and protected Water Vole. Since the introduction of mink, Water Voles have rapidly declined. Recent surveys have found that Water Vole sites have diminished by as much as 94% and are one of the most rapid and serious declines of any British wild mammal during the 20th century.

Creating areas to reintroduce water voles does little more than add an additional item to the menu for mink! The problem has been exacerbated by habitat changes in the Water Vole's natural habitat. Invasive non-native species are estimated to cost well over £2 billion a year in Great Britain.

CAVEAT: We must not think that all non-native species are bad. Indeed it is only a minority that have serious negative impacts on our native British species, our health or our economy.

Invasive species

Many invasive species are in and around our waterways. Zebra Mussel, Signal Crayfish, Mink, Chinese Mitten Crab and American Bullfrog to name a few can have a damaging effect on the infrastructure.

Chinese Mitten Crab. Now established in the Rivers Thames, Medway and Ouse and recorded from several sites throughout England and Wales, including the rivers Tyne, Tamar and Dee and Southfields Reservoir near Castleford, Yorkshire, this is a voracious predator that will consume a range of invertebrate species and the eggs of fish leading to competition with native species and impacting invertebrate and fish populations. It will burrow into river banks, increasing erosion and river turbidity, and causing bank collapse.

American Bullfrog. The bullfrog is one of the most harmful invasive non-native species. It both competes with and eats native amphibians, and carries a disease that has contributed to worldwide amphibian decline and to several global extinctions. It occupies any type of still or slowly moving water, especially where aquatic and bank vegetation are abundant. Now established in the UK.

American Mink. The mink is a semi-aquatic, generalist and opportunist predator with a variable diet that includes aquatic, semi-aquatic and terrestrial prey. Mink are generalist predators of animals such as domestic ducks and poultry, game birds and fish. They take eggs and chicks. They have been linked to the decrease of water voles in Great Britain and cause damage to fisheries. Mink occupy both freshwater and saltwater habitats. Mink habitually follow all kinds of waterways and watercourses but will cross other habitats.

Signal Crayfish. The signal crayfish is much larger than the native white-clawed crayfish. It is well established in England and Wales. The signal crayfish is driving the native white-clawed crayfish towards extinction and causing declines in diversity and richness of aquatic communities. Burrowing by crayfish can cause erosion of riverbanks and destabilise structures built at the edges of rivers. Signal crayfish are found in streams, canals, rivers, lakes and ponds, and are also able to survive in brackish water.

Zebra Mussel. Due to its filtering capacity and ability to produce dense populations, it can significantly reduce native biodiversity, and alter whole freshwater ecosystems. It is also a nuisance and economic problem when growing in pipes of water treatment plants. It forms dense colonies and can be found in both flowing and standing water bodies.

The GB Non-Native Species Secretariat is the authoritative source of information for all invasive, non-native species information in Britain. They have excellent information guides on all the main species, image galleries, notices of events etc. They also act as a good portal to Local Action Groups (LAGs) which are always looking for more help to tackle invasive species.