For years there has been a battle raging in our rivers and on land by aliens intent on domination.
Called Invasive Non-native species (INNS) they are not interplanetary travellers but plants and animals that have arrived from other parts of the globe, and found our countryside to there liking.
Unfortunately few if any of them are welcomed and in some instances they have reeked havoc with our native fauna and flora.
Some have travelled by well meaning environmentalists such as botanists importing plants from around the globe, farmers intent on diversifying their business and others hitched a ride in the ballast water and cargo of ships or even on the sole of your boot .
Species brought here with the intention of farming for their fur such as Mink on the western isles, have had a devastating impact on ground nesting birds.
Another the Signal Crayfish brought here in the 1970s and 1980s for food has expanded its range to much of the UK waters. This species has wiped out the underwater fauna from large stretches of rivers and measures are underway to try to control its spread.
It is unlikely that many of these INNS will be eradicated and the best we can hope for is some measure of control.
A particularly nasty invader is the New Zealand flat worm. This species is now present throughout the mainland and many of the Scottish Islands are infested ( Arran, Skye. Harris and Lewis, Coll, Orkney, Shetland and the Fair Isle).
First introduced on plant material imported to botanical gardens in the 1960s it has the potential to seriously affect agricultural production as it feeds exclusively on earthworms. It has already reduced the population of earthworms in N Ireland to undetectable levels.
We can all play our part in mapping the flatworms distribution which will help in understanding the rate and extent of its spread.
Clearly in the absence of natural predators some of these non-native species can reach plague proportions and have a significant impact on rural economies.
Recent legislation has required landowners and developers to address the problem of a number of particularly damaging INNS.
INNS are referenced in Section 14 of the Wildlife and Countryside Act 1981 (as amended in 2011) when the Wildlife and Natural Environment (Scotland) Act 2011 was enacted.
Through these pieces of legislation it is now an offence to ‘release or allow to escape from captivity any animal to a place outwith its native range; cause any animal outwith the control of any person to be at place outwith its native range; plant or otherwise cause to grow any plant in the wild outwith its native range’.
We all have a responsibility to ensure we take care to avoid spreading these species further and a Code of Practice has been produced by the Scottish Government which outlines our responsibilities.
As ecologists we are often asked for advice on the proper control and management of INNS when encountered on site.
In the north plant species such as Japanese Knotweed, Giant Hogweed and Himalayan Balsaam present particular problems of control and removal and are the INNS most often encountered.
Anyone who has found these species on a development will know that they require careful handling and can be costly to manage and remove. Whether its removal through dig and dump to a licensed facility or chemical control it is important to ensure good bio-security in the movement of plant within the site.
There is often a need to establish areas of quarantine to prevent root material and seed from being spread ‘unwittingly’.
Its not all doom and gloom and a number of non-native species have been credited with helping our native fauna to survive including non-native conifers providing foraging for red squirrels and rabbits providing food for the Scottish Wildcat (on the edge of extinction) and many species of raptors such as Golden eagle.
So the next you’re in your garden keep your eyes peeled you may just be looking at the next alien species preparing to make a break for freedom over the garden fence.