Frequently asked questions

What are alien species?

What are alien species and what "invasive alien species" means? Is there any difference between these two definitions?


Alien species – non-native organisms that become established in a new environment – are on the increase worldwide. Most of them do not present significant risks for their new environment. However, some of them adapt so successfully to the new environment that they become invasive – from being biological curiosities they become genuine threats to local ecosystems, crops and livestock, threatening our environmental and social wellbeing. Invasive alien species are the second leading cause of biodiversity loss, after habitat alteration. They have an economic impact estimated at around € 12 billion per year.

Please provide examples of alien species?

Please provide examples of alien species in Europe and explain what kind of problems these may cause.


It is estimated that 10-15 % of the alien species identified in the European environment have reproduced and spread causing environmental, economic and/or social damage. Species like Giant hogweed, signal crayfish, Zebra mussels and muskrats now impact human health, cause substantial damage to forestry, crops and fisheries, and congestion in waterways. Japanese knotweed for example inhibits the growth of other plants, outcompetes native plants, and seriously damages infrastructure, with huge economic implications. This plant causes € 205 million of damage each year in England, Scotland and Wales.

Why the information network?

Why is so important to build an information network on alien species in Europe?


The need of the network arises from the fact that there is no single database covering all European environments, countries, and taxonomic groups. To overcome the fragmentation a solution is the creation of a network of online interoperable web services through which information in distributed resources can be accessed, aggregated and then used for reporting and further analysis at different geographical and political scales. Harmonization, standardization, conformity on international standards for nomenclature, and agreement on common definitions of alien and invasive species are among the necessary prerequisites.

EASIN information network – the first of its kind in Europe – is an important step to deal with the threat of alien species that become invasive.

Environment Commissioner Janez Potočnik said (2012: "Invasive species are causing growing problems for our natural resources, people's health and the economy. This threat arises from non-native species whose numbers are growing rapidly in an increasingly interconnected world. The EASIN network will help people in Europe in getting better information about where non-native species are, and how common they are – and that will support better policy making on this difficult issue.".

How was compiled the list of alien species found in EASIN?


A first version of the EASIN Catalogue was compiled by harmonizing and integrating information from 43 online databases. Subsequently, this initial compilation of the Catalogue was checked, revised, and updated by taxonomic experts. Currently, an Editorial Board is responsible for changes and updates of the EASIN Catalogue.

What is the term “species status” refers to in EASIN?


This term refers to if a species is ‘alien’, ‘cryptogenic’ or ‘questionable’.
“Alien” species means any live specimen of a species, subspecies or lower taxon of animals, plants, fungi or micro-organisms introduced outside its natural range; it includes any part, gametes, seeds, eggs or propagules of such species, as well as any hybrids, varieties or breeds that might survive and subsequently reproduce.

“Questionable” species are new entries not verified by experts or species with unresolved taxonomic status.

“Cryptogenic” species are those that have no definitive evidence of their native or alien status.

Which system of classification is used for AS pathways in EASIN?


The classification of pathways of introduction currently used by EASIN largely follows the framework proposed by Hulme et al. (2008). Five main pathways have been included (each one divided into more specific sub-categories): 1. Contaminant (Trade of contaminated commodities; Packaging materials; Aquaculture); 2. Corridor (Lessepsian migrants; Inland canals; Railroads and Highways); 3. Escape (Pets, Terrarium-Aquarium species; Zoos, botanical gardens; Cultivation and Livestock; Aquaculture; Ornamental planting; Use of live food-bait); 4. Release (Biocontrol; Game animals; Landscaping-Erosion control; Pets, Terrarium-Aquarium species; Other); 5) Stowaway (Shipping; Aviation; Land transport).

EASIN will gradually align its pathways categorization to the one proposed by the Convention of the Biological Diversity (CBD 2014. Pathways of introduction of invasive species, their prioritization and management. UNEP/CBD/SBSTTA/18/9/Add.1, Montreal, Canada, 23-28 June 2014, 18 pp.), aiming at achieving synchronization and harmonizing of information on Alien Species pathways.

Hulme PE, Bacher S, Kenis M, Klotz S, Kuhn I, et al. 2008. Grasping at the routes of biological invasions: a framework for integrating pathways into policy. Journal of Applied Ecology 45: 403–414,

What are the “primary” and “secondary” pathways?


“Primary” means the pathway(s) of all independent introductions to Europe from regions of their native range.

“Secondary” means the pathway(s) that has/have allowed for species expansion within Europe after introduction through the primary pathway(s) (i.e. from a European region where the species is alien to another European region where the species was not previously present).

What is the “first year of introduction” refers to in EASIN?


It is the year of first observation of an alien species in Europe. It is used as the best available estimate of the year of its initial introduction when the latter could not be determined with certainty, based on a thorough review of the scientific and grey literature.

From where the EASIN maps data originate from?


Records of occurrences are from the EASIN Data Partners and EASIN-Lit.

What kind of information do the EASIN maps depict?


The map shows the occurrences of the selected species in Europe and surrounding seas. In the map it is possible to select different layers (10x10Km grid, Countries, River Basin Districts or Marine Ecoregions) and to filter by Data Partner, time and native range.

How can I retrieve the list of alien species for a specific country?


The retrieval of this information is possible through the EASIN maps for the selected species. The user should click on the specific country and then click on “Total Show species”. The information is downloadable as CSV file, which can be opened in your preferred software (e.g. Excel).

How can I find the source of information of an occurrence record for a specific species?


The retrieval of this information is possible through the EASIN maps for the selected species. The user should click on the specific occurrence area (10x10Km grid, Countries, River Basin Districts or Marine Ecoregions) and the list of Data Partners are depicted in a form of a table. By clicking “Show species” for a specific Data Partner, and then by clicking on the species name, the user can have access to the original source of information.

What is a RESTful Webservice?


The Representational state transfer (REST) technique enables interoperability between computer systems on the internet, independently from the technology adopted by the server exposing the service and the client consuming the service.
A web service can be used automatically, through software capable of extracting and elaborating the data, or manually, which comprises the execution of a query, download of the outcome and conversion in the desired format.
For further information on RESTful web services please refer to