Invasive Alien Species

Preventing the introduction of invasive alien species and managing their impacts is essential to halting biodiversity loss. This issue is also critical to human health, food security, livelihoods and economies.

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A major and growing threat to biodiversity and sustainable development


Invasive alien species are animals, plants or other organisms that are introduced by humans, either intentionally or accidentally, into places outside of their natural range, negatively impacting native biodiversity, ecosystem services or human economy and well-being.

Invasive alien species are one of the biggest drivers of biodiversity loss and species extinctions. Biological invasions also put human health, food security and livelihoods at risk, as highlighted in the United Nations Sustainable Development Goal 15.

The rate of new introductions is growing, as the movement of people and goods around the world increases opportunities to transport species to new environments. At the same time, climate change is making areas more hospitable to new species.

USD 1.288 trillion

- minimum economic cost of biological invasions, 1970 - 2017.

(Diagne, C., Leroy, B., Vaissière, AC. et al., 2021)

1 in 10

species on the IUCN Red List are threatened by invasive alien species.

(The IUCN Red List of Threatened Species, 2022)

Supporting governments, the private sector and civil society to address invasive alien species

Regulating the trade and movement of invasive alien species is the most effective way to prevent their introduction and spread. Once an invasive species arrives to a new area, it is possible to limit their negative impacts though early detection, monitoring and rapid eradication.

The IUCN Secretariat and Species Survival Commission Invasive Species Specialist Group (SSC ISSG) work together to tackle invasive alien species and their impacts at all stages, from providing essential data and expertise to guide policy-making through to action on the ground. We collaborate with regional and national governance, NGOs and local stakeholders.

Knowledge platforms

The Environmental Impact Classification for Alien Taxa (EICAT) is the IUCN global standard for measuring the severity of environmental impacts caused by animals, fungi and plants living outside their natural range. The Global Invasive Species Database is managed by the IUCN Species Survival Commission Invasive Species Specialist Group (ISSG) and the Global Register of Introduced and Invasive Species is an ISSG led initiative. The IUCN Red List of Threatened SpeciesTM also holds information on the impacts of invasive alien species (IAS), and an analysis of how IAS contribute to species global extinction risk can be found here.

Grey Squirrel Introduced to the UK, Ireland, Italy and South Africa, the Gray Squirrel (Sciurus carolinensis) damages trees, and in Europe causes the extinction of Red Squirrel (Sciurus vulgaris) populations through competition and disease. Photo: Tim Blackburn


Invasive alien species in the European Union

IUCN provides technical and scientific support to the European Commission for the implementation of the European Union Regulation (No 1143/2014) on the prevention and management of the introduction and spread of invasive alien species (EU IAS Regulation). 

IUCN has also worked with the European Commission to strengthen the application of the EU IAS Regulation, through creating tools to support the management of vertebrate invasive alien species of Union concern, taking into account welfare implications. This collaboration has resulted in the production of a manual for the management of vertebrate invasive alien species of Union concern, incorporating animal welfare.

Invasive alien species on islands

Island ecosystems are especially vulnerable to the impacts of invasive alien species. In response to the urgent need for action, IUCN implemented the Inva'Ziles project, with input by the IUCN SSC ISSG network, regional networks including the Western Indian Ocean Network on Invasive Species (WIONIS) and the Caribbean Invasive Alien Species Network (CIASNET), hosted by the Indian Ocean Commission and supported by European Commission funding. The resulting Guidelines for invasive species planning and management on islands are aimed at anyone planning a programme to tackle invasive alien species, on islands anywhere.

Naviti island, Fiji Naviti island, Fiji Photo: Alan Tye


Invasive alien species in the marine environment

IUCN works closely with a diverse array of organisations and experts globally, with a shared aim of managing invasive aquatic species and preventing further introductions. This includes working as Strategic Partner on the GEF-UNDP-IMO GloFouling Partnership, alongside the International Council of Marine Industry Associations (ICOMIA) and World Sailing, to produce guidelines and posters on Biofouling Management for Recreational Boating. Recommendations to Prevent the Introduction and Spread of Invasive Aquatic Species.