Invasive species pose a threat to native species. They compete for resources, change habitats and unbalance ecosystems. Also known as exotics, non-natives and introduced species, they are species that have moved outside of their normal distribution. They can be devastating to native populations and are one of the five biggest dangers to biodiversity. While humans sometimes deliberately introduce inasive species, many are accidentally transported on everything from the bottoms of shoes to the hulls of boats.

The impact of invasive species on human health and the economy is also a concern. Every year invasive species cause an estimated 12.5bn Euros worth of damage in Europe alone. The zebra mussel and the quagga mussel for example, while only the size of a fingernail, are wreaking havoc in the UK and the USA by clogging up pipes and changing the chemical makeup of water systems. Other species that are of particular concern to the UK are:

  • the Harlequin ladybird - outcompetes native ladybirds for food
  • the Asian hornet - targets honeybees along with other insects
  • the aptly nicknamed ‘killer shrimp’ - preys on small fish. 

Watch Prof Helen Roy explain more about invasive non-native species:


Oak tree branches
New projects on tree health and plant biosecurity
Foxglove - Simon Smart/CEH
A new paper in Nature reveals for the first time how the abundance of nectar-producing plants has changed since the 1930s across Britain
Nick Isaac of CEH presenting at BES2015
British Ecological Society Annual Conference
National Plant Monitoring Scheme logo
Providing an annual indication of changes in plant abundance and diversity
Some species groups providing critical roles under particular threat
A national focus for terrestrial and freshwater species recording
A boat at Derwentwater
Long-term science in a galaxy far, far away...
Owen, Oli and Jodey in Akrotiri forest
A COST Action Short-Term Scientific Mission
Parus major, great tit, on a branch
Potential ecological impacts of changes to nature's calendar
Cameraria orhidella, horse-chestnut leaf-miner moth
Citizen scientists asked to help track spread
Michael Pocock with students investigating a horse chestnut tree
La Sainte Union school students write about Michael Pocock's visit
Helen (centre) with Phd students Sandra Viglasova (left) and Katie Murray (right) at the 2015 Verrall Supper.
Helen Roy writes about her new membership to the Entomological Club