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:


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
The Opera House in Lille, the capital of French Flanders
UK and France come together in Lille for international conference
Scots pine tree by a roadside, Sheildaig
Sustainable approaches for addressing threats to trees
Dr Helen Roy reveals why she is fascinated by Hesperomyces virescens and Harmonia axyridis.
Sexually transmitted infection is spreading in harlequin ladybirds
Harlequin succinea larvae and adults. Photo: William Ritson
Over 23,000 recordings show a preference for sunny cities
Invasive quagga mussels clogging a propellor
First sighting of the most threatening invasive species