International Association
for Open Knowledge
on Invasive Alien Species

What are Invasive Alien Species?

Invasive Alien Species (IAS) are any species that are not native to an area but which are able to establish themselves and often spread quickly, causing environmental or economic damage. In its native range, a species will be kept in check by environmental factors and predators. In a new territory, without those same controls, it can thrive and take over. When IAS are successful, they use up resources quickly, outcompeting other native species and altering the ecosystem.

Many people believe that the spread of IAS is a natural occurrence and that we should allow nature to take its course. For the IAs issue, we are only concerned with harmful species that are spread by human activity, either intentionally or unintentionally and become invasive. There are many pathways by which species can spread, but some of the most common ones are the trade of goods and materials, the shipping industry, and recreational activities.

Why are Invasive Alien Species a problem?

IAS are one of the biggest threats to biodiversity worldwide, and we need biodiversity! Native species evolve and adapt to form their own unique niche, and a delicate balance is required to keep all elements of the environment functioning in a healthy way. IAS alter that delicate balance. In many cases invasive species can displace a similar native species by competition or can carry a disease that can kill the native. The crayfish plague, carried by invasive crayfish, has resulted in the extinction of the white clawed crayfish in many European countries.

Impacts can also be economical, e.g. invasive alien crop pests can reduce agricultural yields. Biofouling shellfish, e.g. zebra mussel, can block water abstraction pipes.

Growing global trade and transport creates ever increased risks of spread. Once an IAS is established, it is usually impossible, or economically prohibitive, to eradicate. Management then becomes an ongoing issue, with a high cost. The estimated associated cost of IAS management in the EU is 12 billion per annum.

Invasive Alien Species (IAS)
Establish in an area to which it is not normally native
Spread by a number of pathways
Cause environmental and/or economic damage

Biodiversity is Good
A wider variety of species gives us a wider variety of crops
Healthy biodiversity provides food and shelter for all living things
Healthy ecosystems are more resilient to disasters and sudden changes

Biosecurity is important
Prevention is better than cure
IAS cannot invade new areas without human help
Once native species are displaced by IAS, they may never re-establish in the area.