Invasive alien species that threaten wildlife have cost the Northern Ireland economy an estimated £46.5 million a year, the Environment Minister has revealed.
Alex Attwood said the detrimental effects of nuisance breeds such as Japanese knotweed, Zebra mussels and floating pennywort were economical as well as ecological. They pose a risk to unique flora and fauna, forestry, fishing, and farming.
"Increasing awareness of the threat of invasive species and the need to tackle them is key to achieving success," Mr Attwood said.
"In Northern Ireland we have been subject to the impacts of invasive species that have been introduced over hundreds of years. Our ancestors in Victorian times for example introduced several invasive plant species such as Japanese knotweed and Giant hogweed which are now widely established.
"In the past 20 years we have also seen an increase in the numbers of invasive aquatic plants and invasive marine species being detected in our environment," the minister said.
An invasive alien species is one that has been introduced to a country where it is not native and through rapid spread causes widespread damage to the local species. Some species were intentionally introduced before their harmful impacts were known while others have arrived as hitchhikers.
Among the most difficult to tackle has been the Japanese knotweed, which can tear through concrete, tarmac and buildings and has cost millions of pounds each year to control. Zebra mussels have also caused problems for wildlife and the fishing industry in some of Northern Ireland's most popular waterways including Lough Neagh and Lough Erne.
The introduction of the grey squirrel in the 19th century is one of the best known examples of invasion by an alien species. It has the ability to carry the squirrel pox virus which is lethal to native red squirrels. Efforts to eradicate the highly invasive floating pennywort - an aquatic plant that can grow at a rate of 20 centimetres a day - have been successful at two sites in Northern Ireland to date.
Large scale control measures have also been put in place at five other areas including the Faughan river, the Clanrye river, the Newry canal and the Ballinmallard river but there are still issues at Glastry Clay Pits on the Ards Peninsula. It is hoped a new strategy will help Government officials tackle the problems caused.
Mr Attwood said: "The key to solving this is partnerships, with government, community and environment groups working in tandem. There remains much still to do to tackle this threat and to protect our environment from both the present and potential threats of invasive species."