THEY are one of the greatest threats to biodiversity worldwide, second only to habitat loss. It has been estimated that they cost the UK economy billions of pounds a year.

THEY are one of the greatest threats to biodiversity worldwide, second only to habitat loss. It has been estimated that they cost the UK economy billions of pounds a year. Some even pose a direct threat to our health. Yet most people are completely unaware of the insidious invasion of alien species.

Areas such as the Broads are particularly at risk from invasive alien weeds such as New Zealand pigmyweed and floating pennywort; these can choke waterways, increase the risk of flooding and out-compete our native species. Other invasive alien species are also cause for concern. The native white-clawed crayfish, for example, is being pushed to the brink of extinction in many areas by the invasive North American signal crayfish. On land, rhododendron - which originally came from South Asia - can spread rapidly to dominate an area and prevent the re-growth of native plants by releasing toxic chemicals.

To help address the impacts of invasive alien species, the Norfolk Biodiversity Partnership launched the Non-native Species Initiative in September 2008. This is one of very few projects in Britain designed to promote the active management of invasive alien species at a county-level, and - if successful - could become a potential model of best practice.

Next Wednesday, the initiative is holding a stakeholders' forum to provide an opportunity for those with an interest in the management of invasive alien species to discuss how we should deal with them in the future. A range of experts, including Huw Thomas, head of protected and non-native species at Defra, will outline action being taken to address the problem at a national level. Case studies from Norfolk, such as the �17,000 project to eradicate floating pennywort from the River Waveney, will also be presented.

Michael Sutton-Croft, co-ordinator of the Norfolk Non-native Species Initiative, said: “While significant progress has been made in addressing the other threats to biodiversity within Norfolk, such as habitat loss and degradation, there has been little concerted effort to address the problems posed by invasive alien species. The Norfolk Non-native Species Initiative will promote and guide action, ensuring that we make the best use of our existing capacity. The Stakeholders' Forum will provide a unique opportunity for members of local conservation groups to meet with and learn from nationally and internationally respected experts in this field.”