Invasive non-native species
Non-native species pose a risk to our native species and the environment. Many have reached numbers and distribution that mean reversal is unlikely.
An example is the introduction of the grey squirrel. They were introduced to the UK initially by Thomas Brocklehurst in 1876 when he released a pair into his estate as an 'ornamental' species. Since then they have become the dominant species pushing the native red squirrels out of most of England and Wales. Grey squirrels carry squirrel pox, which they are immune to, but red squirrels are not.
Similarly, signal crayfish have almost eradicated the native white clawed crayfish from most of its original range because it carries the crayfish plaque. Signal crayfish are immune but our native crayfish are not. American mink escapees from fur-farms have also become established across much of Britain contributing to the decimation of water vole numbers. Fallow, chinese water and muntjac deer releases have, in the absence of natural predators, led to their uncontrolled spread across the UK. They cause damage to the understorey plants and saplings in native woodland. They have reached numbers and distribution that mean reversal is unlikely.
We have also had problems with the asian topmouth gudgeon introductions which are harmful to native fish. Their rapid breeding cycle soon out-competes native fish. However, stringent work by the Environment Agency and its limited range so far suggests that in this case their spread might be halted. Eradication programs have already shown good results, but at a price.
Plants can be a problem too. Japanese knotweed, introduced as an ornamental plant, is now a serious problem throughout the UK. We have also had instances of giant hogweed, which in invasive in some parts of the UK and can cause severe skin burns. There are a range of plants which are becoming problematic in Southampton such as the:
- 'Parrot feather' (myriophyllum aquaticum)
- American skunk cabbage (lysichiton americanus)
- Himalayan Balsam (impatiens glandulifera)
So care must be taken when disposing of garden waste so as not to accidentally introduce garden plants into natural spaces.
In Southampton we have instances of illegally introduced non-natives in many of our sites. Notably red-eared terrapins in Millers Pond and Shirley Pond. These are cast out when people tire of their pets. Terrapins have limited impact and are not thought to breed in the UK. However, it is not an ideal environment for them and it is not good for their own welfare. Goldfish have also been dropped into most of our ponds. Fish already existing in the ponds have lowered immunity as they do not get exposed to disease. Introducing new fish, which might carry diseases that they have resistance to, could introduce a disease to the existing population. If you can no longer take care for your pet, pet shops are usually happy to take them back. Failing that ask the Blue Cross or RSPCA, or a number of other specialist rescuers who will re-home them. One example in Dorset is Turtle Paradise.
For more information on non-native species visit the Non-Native Species Secretariat.
