Pathways of introduction of marine non-indigenous species to European seas

Indicator Specification
Indicator codes: MAR 003
Created 29 Mar 2019 Last modified 03 Sep 2019
17 min read
This indicator describes the processes (pathways) that result in the transfer of alien species from one location to another. The identification and categorisation of pathways follows the Convention on Biological Diversity (CBD) classification as interpreted by the IUCN (2017). A hierarchical approach has been adopted to describe the pathways, based on the framework developed by Hulme et al. (2008). The three broad pathways shown above, in which a NIS can arrive, can be subdivided into six: importation of a commodity; arrival of a transport vector; or spread from a neighbouring region. Six principal pathways were identified under the CBD process (UNEP, 2014) as quoted below. Pathways related to transport of a commodity: 'Release in nature' refers to the intentional introduction of live alien organisms for the purpose of human use in the natural environment. Examples include for biological control; erosion control (and dune stabilisation); fishing or hunting in the wild; landscape 'improvement'; and the introduction of threatened organisms for conservation purposes. 'Escape; refers to the movement of (potentially) invasive alien species from confinement (e.g. aquaria; aquaculture and mariculture facilities; scientific research or breeding programmes). Through this pathway, the organisms were initially purposefully imported or otherwise transported to the confined conditions, but then escaped from such confinement, unintentionally. This may include the accidental or irresponsible release of live organisms from confinement, including cases such as the disposal of live food into the environment or the use of live baits in an unconfined water system. 'Transport–Contaminant' refers to the unintentional movement of live organisms as contaminants of a commodity that is intentionally transferred through international trade, development assistance, or emergency relief. This includes pests and fisheries as well as contaminants of other products. Related to a transport vector: 'Transport–Stowaway' refers to the moving of live organisms attached to transporting vessels and associated equipment and media. The physical means of transport-stowaway include various conveyances, ballast water and sediments, bio-fouling of ships, boats, offshore oil and gas platforms and other water vessels, dredging, angling or fishing equipment. Recreational boating is also included under this pathway. Corridor refers to the movement of alien organisms into a new region following the construction of transport infrastructures, in whose absence the spread would not have been possible. Such trans-bio-geographical corridors include international canals (connecting river catchments and seas).  'Unaided; refers to the secondary natural dispersal of invasive alien species that have been introduced by means of any of the foregoing pathways. While the secondary dispersal is unaided, it can only take place because of a previous human intervention. Information on the mechanisms of the secondary spread of invasive alien species, after their introduction, are relevant to define the best response measures. In this analysis, for simplicity and to be more specific to the marine environment, we used the first five categories. The fifth (Transport-Stowaway) was further subdivided into ballasts, fouling and other (offshore oil and gas platforms, and other water vessels, dredging, angling or fishing equipment). Trends in primary pathways over 6 year periods should tell a story when combined with management policies applied/implemented over the last decades.

Assessment versions

Published (reviewed and quality assured)
  • No published assessments

Rationale

Justification for indicator selection

Non-indigenous species (NIS) are alien plants, animals or other organisms, introduced as a consequence of human activities outside their native range. NIS have been systematically observed since the early 1990s, and their introduction into Europe’s seas has happened at unprecedented rates (Hulme et al., 2008).

NIS may arrive and enter a new region through three broad pathways: import of a commodity (e.g. aquaculture), arrival of a transport vector (mostly shipping), and/or natural spread from a neighbouring region where the species is itself alien. The introduction of species into habitats outside their native ranges is closely linked to the increasing globalisation of trade and travel (Mooney & Hobbs 2000). Once introduced, alien species have a high probability of establishment and spread. While there is a consensus that shipping, along with aquaculture, are the primary drivers for NIS introductions, and a key locus for preventive regulation, few policies have been evaluated by scientists for their effectiveness.

Historically, aquaculture and stock transfers of aquatic species resulted in a significant amount of taxa being transported worldwide (Nentwing, 2007). The speed and access of different transport modes in the spread of cultured species, their pests, parasites, diseases and associate species, have changed over this time. At one time shipping journeys would have taken some months but now aircraft can spread biota within a day or less over the same distances. Elton (1958) stated: 'the greatest agency of all that spreads marine animals to new quarters of the world must be the business of oyster culture'. He was unaware of the impact that shipping will already have had by that time and of the trade that was to follow.

Knowledge of the invasion process is essential for designing management plans to cope with the potential detrimental effects of invasive species, and to attempt to prevent their large-scale spread. The present work addresses trends in pathways/vectors for alien species in the marine and estuarine environment.

Scientific references

Indicator definition

This indicator describes the processes (pathways) that result in the transfer of alien species from one location to another. The identification and categorisation of pathways follows the Convention on Biological Diversity (CBD) classification as interpreted by the IUCN (2017).

A hierarchical approach has been adopted to describe the pathways, based on the framework developed by Hulme et al. (2008). The three broad pathways shown above, in which a NIS can arrive, can be subdivided into six: importation of a commodity; arrival of a transport vector; or spread from a neighbouring region. Six principal pathways were identified under the CBD process (UNEP, 2014) as quoted below.

Pathways related to transport of a commodity:

  1. 'Release in nature' refers to the intentional introduction of live alien organisms for the purpose of human use in the natural environment. Examples include for biological control; erosion control (and dune stabilisation); fishing or hunting in the wild; landscape 'improvement'; and the introduction of threatened organisms for conservation purposes.
  2. 'Escape; refers to the movement of (potentially) invasive alien species from confinement (e.g. aquaria; aquaculture and mariculture facilities; scientific research or breeding programmes). Through this pathway, the organisms were initially purposefully imported or otherwise transported to the confined conditions, but then escaped from such confinement, unintentionally. This may include the accidental or irresponsible release of live organisms from confinement, including cases such as the disposal of live food into the environment or the use of live baits in an unconfined water system.
  3. 'Transport–Contaminant' refers to the unintentional movement of live organisms as contaminants of a commodity that is intentionally transferred through international trade, development assistance, or emergency relief. This includes pests and fisheries as well as contaminants of other products.

Related to a transport vector:

  1. 'Transport–Stowaway' refers to the moving of live organisms attached to transporting vessels and associated equipment and media. The physical means of transport-stowaway include various conveyances, ballast water and sediments, bio-fouling of ships, boats, offshore oil and gas platforms and other water vessels, dredging, angling or fishing equipment. Recreational boating is also included under this pathway.
  2. Corridor refers to the movement of alien organisms into a new region following the construction of transport infrastructures, in whose absence the spread would not have been possible. Such trans-bio-geographical corridors include international canals (connecting river catchments and seas).
  3.  'Unaided; refers to the secondary natural dispersal of invasive alien species that have been introduced by means of any of the foregoing pathways. While the secondary dispersal is unaided, it can only take place because of a previous human intervention. Information on the mechanisms of the secondary spread of invasive alien species, after their introduction, are relevant to define the best response measures.

In this analysis, for simplicity and to be more specific to the marine environment, we used the first five categories. The fifth (Transport-Stowaway) was further subdivided into ballasts, fouling and other (offshore oil and gas platforms, and other water vessels, dredging, angling or fishing equipment). Trends in primary pathways over 6 year periods should tell a story when combined with management policies applied/implemented over the last decades.

Units

The units used in this indicator are:

  • Number of new alien species arriving in European Seas since 1970 per pathway/vector over 6-year periods.
  • Breakdown of trends over 6-year periods per Regional Sea and Marine Strategy Framework Directive (MSFD) area.

Policy context and targets

Context description

Invasive species are addressed in European and global legislation.

The MSFD (Directive 2008/56/EC amended by 2017/845/EC), which is the environmental pillar of the EU Integrated Maritime Policy, sets an overall objective to reach or maintain 'Good Environmental Status' (GES) in European marine waters, by 2020. One of the objectives addresses ‘Non-indigenous species introduced by human activities, that shall be at levels that do not adversely alter the ecosystems’. The MSFD aims to set up an effective management system to prevent further introductions and limit the impacts of NIS already introduced (EU, 2017) and addresses:

-          newly-introduced non-indigenous species;

-          established non-indigenous species, particularly invasive non-indigenous species; and

-          species groups and broad habitat types that are at risk from non-indigenous species.

The EU Regulation (EU, 2014) addresses exclusively invasive alien species (IAS) and aims to increase coordination among existing legal instruments. It includes innovative pathway-related measures, aiming to provide a holistic framework for the assessment, management and prevention of NIS.

Other legislation relevant for management of NIS includes: Regulation (708/2007/EC) on the use of alien and locally absent species in aquaculture; Regulation (338/97/EC) on the protection of species of wild fauna and flora by regulating trade; Directive (2000/29/EC) on protective measures against the introduction of organisms harmful to plants or plant products; and Water Framework Directive (2000/60/EC) in the filed water policy.

A number of International policies are in place. The Convention on Biological Diversity (CBD, 2014), adopted in the EU by  the Biodiversity Strategy (COM(2011) 244 final) has the overall objective of halting biodiversity loss and also addresses the reduction in the impacts of alien species. The EU Biodiversity Strategy 2020 Target 5, states that 'By 2020, IAS and their pathways are identified and prioritised, priority species are controlled or eradicated and pathways are managed to prevent the introduction and establishment of new IAS' (EC, 2011).

Shipping is an important vector for NIS introduction, addressed by the ballast waters convention implementation (IMP, 2017; IUCN, 2017) The convention entered into force in 2017, meaning that ships must manage their ballast water so that aquatic organisms and pathogens are removed or rendered harmless before the ballast water is released to a new location. This will help prevent the spread of invasive species as well as potentially harmful pathogens (International Maritime Organization (IMO)).

Regional Seas Conventions contribute to implementing this through supporting the ratification and implementation of IMO conventions.

The number of alien species is highest in the Mediterranean, where countries agreed on the Action Plan concerning Species Introductions and Invasive Species (UNEP MAP, 2017), because of the Suez Canal and Lessepsian migration from the Red Sea (Fox, 1924), in conjunction with the Aswan Dam construction in the 1960s. This construction removed the protection zone for the spread of IAS throughout Suez, represented by the freshwater buffer in the Nile River (Zakaria, 2015). Until the construction of the dam, this water was a relatively effective control of NIS.


Targets

  • Reduce the number of NIS intentionally imported (Release) and accidentally introduced with aquaculture imports (Escape from contaminant): regulations (708/2007);
  • Reduce the number of NIS transferred in ship ballasts and as fouling (IMO, 2017);
  • Reduce the number of NIS spreading via man-made inland and marine corridors;
  • Prevent spreading of NIS imported for the aquarium trade — private/public (Escape from contaminant), (CITES Convention);
  • Prevent spreading of NIS from one regional sea to another — secondary introduction;
  • Prevent new introductions of harmful species to European Seas (EU Regulation (No 1143/2014).

Related policy documents

Key policy question

Are policies for controlling the pathways of marine biological invasions effective?

Methodology

Methodology for indicator calculation

The list of species used for the analysis is the same as that considered for the trends in the introduction analysis (EEA indicator MAR002 https://www.eea.europa.eu/data-and-maps/indicators/trends-in-marine-alien-species-mas-2/assessment) and stored in the HCMR/EEA database. It includes both alien and cryptogenic species. The information on the country, year of first introduction of each species and pathway/vector is publicly available through the species search widgets in EASIN, updated on 27/3/2018, Version: 7.1 (https://easin.jrc.ec.europa.eu/easin) see Tsiamis et al. (2017). The HCMR/EEA database is in full agreement with the pathway classification given in EASIN, and updated for new species to May 2018.

The following European alien species data bases have been used for defining possible pathways:

Trends in introduction per pathway were calculated on a 6-year basis, considering the very first sighting/collection of the species in European Waters/regional Sea/MSFD area. In the absence of exact collection dates, the date of publication was used as the best available information. All alien species — invasive, established and casual — were taken into account.

The primary pathway/vector was filled in as far as possible. Marine and estuarine species are those aquatic species that do not complete their entire life cycle in freshwater (modified after ICES, 2005). Cryptogenic, range expanding and vagrant species are not considered in the analysis. Thus, the primary pathway was calculated for 876 species that were introduced since 1970. However, on calculating the trends at regional/MSFD level, the secondary pathway was also considered in cases where a species spread unintentionally or by another mode of introduction than the original one in the first recipient EU area.

To categorise pathways of primary introduction of alien species into a new region, we have followed the framework proposed by CBD (2014), as described in the 'Indicator definition' section .

Given the potential multiple ways of introduction at pan-European level, some species can show more than 100 % of their potential, since they are linked to more than one pathway.

Methodology for gap filling

Unless species are found when deliberately moved, evidence of their actual transmission is seldom known.

Information on vectors is mostly derived from expert judgement on an extensive review of the referred databases, since specific research projects aimed at identifying vectors and occurrences are complicated and demand large resources. The only exception is published reports issued on maritime traffic worldwide (BWM, 2005). In a large number of cases, likely pathways are merely inferred, for example, taking into account the most common activity occurring in a specific location (shipping, aquaculture), but no scientific evidence is provided.

Vertebrate pathways tend to be characterised as deliberate releases. With the exception of the Lessepsian immigrants that arrived unintentionally via the Suez Canal, invertebrates were introduced mostly as contaminants and plants as escapees. Pathogenic microorganisms and fungi are generally introduced as contaminants of their hosts.

Methodology references

Uncertainties

Methodology uncertainty

In many cases, it is impossible to identify the introduction vector. Thus, the pathway of 32 species is assigned as ‘unknown’. In bivalves, for example, introductions may be attributed to larval transport in ballast water releases, adults in hull fouling of ships or imports of stock for aquaculture purposes, or for direct human consumption but released into the environment

For species that are most frequently associated with hull fouling, this form of transport was assumed to be the responsible vector. For planktonic taxa and microscopic resting stages, we have deemed ballast water to be the most likely vector since such species that are associated with hull fouling might be expected to become flushed away during ship journeys at sea. Human activities near to the site of the first records are generally assumed to be responsible for an introduction event. However, such deductions are not always secure and for this reason we have calculated more than one vector where the likely vector remains unclear.

Where more than one pathway of introduction is suspected/documented, the analysis has considered both modes of introduction. Thus, the resulting percentage of contribution per pathway amounts to more than 100 %.

Data sets uncertainty

See rationale uncertainty

Rationale uncertainty

Different levels of certainty are associated with alien species that areintroduced. A scheme proposed by Minchin (2007) and adopted by Katsanevakis et al. (2013), provides a basis for an improved quality of information for pathways and vectors.

(1)     There is direct information of a pathway/vector: the species was clearly associated with a specific vector(s) of a pathway at the time of introduction to a particular locality. This is the case in intentional introductions (i.e. aquaculture/commodity) and in many cases of Lessepsian immigrants (when there was direct evidence of a gradual expansion along the Suez Canal and then in the localities around the exit of the Canal into the Mediterranean).

(2)     A most likely pathway/vector can be inferred: the species appears for the first time in a locality where a single pathway/vector is known to operate and there is no other rational explanation for its presence except by this pathway/vector. This applies to many species introduced by shipping or aquarium trade or as aquaculture contaminants. In some cases, a specific vector could not be inferred, e.g. some species probably introduced by shipping could not be further linked to ballasts or hull fouling and were classified as ‘shipping/unknown’. In many cases, inference is based on known examples of introductions elsewhere for the same or similar species, the biology and ecology of the species, the habitats and locales it occupies in both the native and introduced range, and its pattern of dispersal (if known), e.g. for a fouling species frequently recorded in ports, shipping has been assumed to be the most probable vector.

(3)     One or more possible pathways/vectors can be inferred: the species cannot be convincingly ascribed to a single pathway/vector. Inference is based on the activities in the locality where the species was found and may include evidence on similarly behaving species reported elsewhere.

(4)    Unknown: where there is doubt as to any specific pathway explaining an arrival. The pathway of 32 species has been assigned as ‘unknown’.

 

References

  • Katsanevakis S, Zenetos A, Belchior C, Cardoso AC., 2013. Invading European seas: assessing pathways of introduction of marine aliens.Ocean and Coastal Management, 76: 64–74.

http://www.sciencedirect.com/science/article/pii/S0964569113000562



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General metadata

Responsibility and ownership

EEA Contact Info

Monika Peterlin

Ownership

European Environment Agency (EEA)

Identification

Indicator code
MAR 003
Specification
Version id: 2

Frequency of updates

Updates are scheduled every 3 years

Classification

DPSIR: Pressure
Typology: Policy-effectiveness indicator (Type D)

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Data references used

Relevant policy documents

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