What is an Invasive Alien Species?
An alien species is a species introduced by humans – either intentionally or accidentally - outside of its natural past or present distribution, however not all alien species have negative impacts, and it is estimated that between 5% and 20% of all alien species become problematic. It is these species that are termed ‘invasive alien species’ (IAS).
"An invasive alien species (IAS) is a species that is established outside of its natural past or present distribution, whose introduction and/or spread threaten biological diversity” Convention on Biological Diversity.
What are their impacts?
Invasive alien species are a major driver of biodiversity loss. In fact, an analysis of the IUCN Red List shows that they are the second most common threat associated with species that have gone completely extinct, and are the most common threat associated with extinctions of amphibians, reptiles and mammals.
An example is the Micronesian Kingfisher Todiramphus cinnamominus which was endemic to the island of Guam, but following predation by invasive alien snakes (Brown tree snake Boiga irregularis) it became Extinct in the Wild in 1986 when the last remaining wild birds were taken into captivity for captive breeding. In fact the Brown tree snake has caused many extinctions on Guam, including the local extinction of over half of Guam’s native bird and lizard species as well as two out of three of Guam’s native bat species.
Invasive alien species can also lead to changes in the structure and composition of ecosystems leading to significant detrimental impacts to ecosystem services, affecting economies and human wellbeing. For example the water hyacinth Eichhornia crassipes, a native to South America is spreading across Africa, Asia, Oceania and North America. It is a fast growing floating aquatic plant forming dense mats on the water surface, limiting oxygen and preventing sunlight reaching the water column. Infestations have led to reduced fisheries, blocked navigation routes, increased cases of vector bourne diseases, reduced hydropower capacity and affecting access to water.
Biological invasions are on the increase
Due to the increase in the movement of people and goods around the world, the opportunity for the introduction of species outside of their natural range is on the increase. The different ways in which species are transported from one place to another, are called ‘pathways’. Common pathways include the release of fish for fisheries into the wild, escape from farms and horticulture, within ship ballast water and the spread through man-made corridors such as canals.
Even though the number of documented IAS in many countries is underestimated, there has been a significant increase in invasive species introductions. For example within Europe the numbers of invasive alien species has increased by 76% between 1970 and 2007.
What is being done?
In 2010 almost all of the world’s governments adopted the Convention on Biological Diversity Strategic Plan for Biodiversity, which included 20 headline ‘targets’ referred to as the Aichi Targets. One of these targets (#9) is specifically related to IAS.
“Target 9: By 2020, invasive alien species and pathways are identified and prioritized, priority species are controlled or eradicated and measures are in place to manage pathways to prevent their introduction and establishment” Convention on Biological Diversity
This international commitment to addressing IAS was re-affirmed in 2015 through the 2030 Agenda for Sustainable Development which includes 17 goals (SDGs) each with specific targets. The SDGs have nature woven throughout acknowledging that nature is fundamental to human well-being. One of the SDGs #15 Life on land, has a target focusing specifically on IAS.
“By 2020, introduce measures to prevent the introduction and significantly reduce the impact of invasive alien species on land and water ecosystems and control or eradicate the priority species”
Governments, other organisations, the private sector and civil society all have a role towards achieving these targets. The underlying concept of addressing IAS and their impacts is that the most effective and cost efficient way is to prevent the introduction in the first place through the management of ‘pathways’, for example through regulation of trade or movement of certain species. Once an IAS has arrived it is critical that the species is detected early, monitored and if necessary eradicated or contained. If an IAS becomes established and widespread, it can be very costly and difficult to eradicate and often mitigation of the impacts of the IAS is the only option.
What is IUCN doing to address IAS?
IUCN’s work on IAS is focused primarily on achieving Aichi T9. To do this IUCN has been working in three major areas, providing scientific knowledge, engaging in and supporting national and regional policy development, and action on the ground.
Invasive Species Specialist Group (ISSG)
Much of the work IUCN undertakes on IAS is through the Invasive Species Specialist Group (ISSG), which is a global network of scientific and policy experts on invasive species. Organized by the IUCN Species Survival Commission, the ISSG aims to reduce threats to natural ecosystems and the native species they contain by increasing awareness of invasive alien species and ways to prevent, control or eradicate them.
IAS Knowledge Products
IUCN has developed a number of knowledge products [databases] which provide critical support to decision making processes related to IAS.
The Global Invasive Species Database
The Global Invasive Species Database (GISD) is a free, online searchable source of information about alien and invasive species that negatively impact biodiversity. The GISD aims to increase public awareness about invasive species and to facilitate effective prevention and management activities by disseminating specialist’s knowledge and experience to a broad global audience. It focuses on invasive alien species that threaten native biodiversity and natural areas and covers all taxonomic groups from micro-organisms to animals and plants.
The Global Register of Introduced and Invasive Species
The Global Register of Introduced and Invasive Species (GRIIS) compiles annotated and validated country-wise inventories of introduced and invasive species. The development and population of the GRIIS was undertaken by the ISSG within the framework of the CBD Global Invasive Alien Information Partnership.
IAS Knowledge Products under development
Island Biodiversity and Invasive Species Database
The Island Biodiversity and Invasive Species database (IBIS) aims to record and provide information on the occurrence, biological status and impacts of invasive alien species on native species on islands (with a focus on those that are classified as ‘threatened’ in the IUCN Red List of Threatened Species- and on National Red Lists) and the prevention and management of this threat.
IAS Pathways Management Resource
ISSG is working with partners on a prototype online resource that is focused on ‘Pathways of introduction and spread of invasive alien species’. The Invasive Alien Species Pathway Management Resource is under development and will include information on species pathways and any legal information related to the management of specific pathways.
Classifying the environmental impact of different IAS
The IUCN ISSG and IUCN members are working with the scientific community to develop an objective and transparent method for classifying alien species in terms of the magnitude of their detrimental environmental impact. This is currently in the early stages of implementation and testing.
The overarching aim of all IUCN policy engagement work related to IAS is to provide technical and scientific advice to work towards achieving Aichi Target 9. IUCN and the ISSG aim to encourage and mainstream invasive species issues across different fora, including national governments, international policy instruments such as the Convention on Biological Diversity, the private sector and civil society. The ISSG membership also provides technical and scientific advice to national and regional agencies in developing policy and strategies to manage the risk of biological invasions.
Action on the ground
IUCN also undertakes projects on the ground to develop capacity, and generate knowledge and best practice on IAS issue. One current project is the 'Preparation and testing of a comprehensive model for preventing and managing the spread of invasive species on island ecosystems' also known as the Inva’Ziles Project which has been funded by the European Commission - EuropAid. IUCN is working with organisations in the Western Indian Ocean (WIO) to develop capacity and networks for preventing and managing biological invasions, and developing best practice through IAS management at key sites. The Western Indian Ocean Network on Invasive Species (WIONIS) was launched in 2012 and has a functioning e-mail list server for those working on IAS issues across the WIO. The e-mail list is managed by WIONIS members and the Inva’Ziles Project, hosted by the ISSG at the University of Auckland. The project is also developing a WIONIS web portal which will offer information on IAS in the region, including a space for blogs and a forum to exchange experiences and advice, a gallery page to aid the identification of species, and a bibliographic database and depository for pertinent literature, including otherwise unpublished documents.