Thursday, 22 August 2013

Invasive Species II

Continued form  Invasive Species I 

Previously I said "Call me old and cynical, but maybe the latest of CaRT's ideas the 'Great Nature Watch' is a bit of lip service to placate the prospective punters. Now, you might think with CaRT getting all 'touchy feely' over ecological and environmental issues. The invasive stuff would be high on the agenda of protecting hundreds of miles of waterways habitat. You might think that getting rid of the invasive species was much more important in protecting habitat. Much more important than concentrating on voles and shrews. But then the cute furry little critters will help with the dash for the punters cash, much more than an appeal for money to combat Knotweed."

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 item to the menu for mink! The problem has been exacerbated by habitat changes in the Water Vole's natural habitat. Changes in habitat brought about by invasive species like Japanese Knotweed.

Invasive non-native species are estimated to cost well over £2 billion a year in Great Britain. Just a few examples of recent costs associated with invasive non-native species include a predicted £1.56b to eradicate Japanese Knotweed nationwide.£2m spent to eradicate Japanese Knotweed on a 2 hectare development site.£11m to eradicate rhododendron from a national park in Wales. £13.9m of damage per year caused by deer vehicle collisions (many of which were non-native species) £120,000 spent by one water works on modifications to cope with Zebra Mussels. £160m estimated to be spent on weed control in one year in the UK. £10m estimated cost to British timber industry of squirrel damage to beech, sycamore and oak woodland.£1m delay caused to a road development scheme while waiting to treat Japanese Knotweed.

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. 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. Can impact marine and freshwater ecosystems. 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. 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. Established in the UK.

American Mink. The mink is a semi-aquatic is a 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 GB 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.The signal crayfish 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.

For information Click Here

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