Cumulative Effects Assessment for Non-Indigenous Species
The bow-tie diagram for non-indigenous species (NIS) (Figure CE.1) aligns with the DAPSIR narrative in the Thematic Assessment (provisional confidence assessment: Medium (Medium Agreement on DAPSIR content + Medium Evidence to support connections) based on the approach described in Agreement 2019-02).
The bow-tie analysis for NIS shows the relationships between the DAPSIR components which need to be considered in a cumulative effects assessment. Human activities which contribute to the introduction and spread of NIS pressures with the potential to both individually and cumulatively contribute to biodiversity state changes have been identified in the following thematic assessments:
Benthic Habitats Input of NIS: The direct or indirect introduction of NIS, for example Chinese mitten crabs, slipper limpets, Pacific oyster and their subsequent spread and out-competing of native species. Ballast water, hull fouling, and stepping-stone effects (e.g. offshore wind farms) may facilitate the spread of such species. This pressure could be associated with aquaculture mussel or shellfishery activities, either through the use of imported seed stock or from accidental releases.
Pelagic Habitats : Coastal and offshore structures provide substrate for meroplankton, including NIS, to colonise, and discharges of ballast water from shipping contributes to their introduction and spread.
Fish The introduction and spread of NIS through international shipping, fishing, aquaculture, aquarium trade and canal construction / operation (Woods et al., 2016). Invasive species can affect food web dynamics, displace native species, introduce diseases and lead to changes in habitat type, thereby significantly altering marine ecosystems (Crain et al., 2009; Gestoso et al., 2018).
Marine Birds : Breeding colonies of birds can be pressured by invasive non-indigenous mammalian predators. Predation of eggs and young birds can cause reductions in breeding success and could lead to the desertion of whole colonies. In the OSPAR area, seabird colonies are at risk from introduced non-native predatory mammals such as brown rats, cats and American mink, and also from native mammals such as hedgehogs, stoats and foxes which have been introduced by humans to offshore islands.
Marine Mammals : the introduction and spread of NIS have been linked to alterations in reproductive rates in marine mammals.
Input of litter (solid waste matter, including micro-sized litter) [Substances, litter and energy]: Marine litter can contribute to the input/spread of NIS by providing mobile artificial substrate that can transport non-indigenous species from location to location.
The State section describes the potential ecological impacts associated with the introduction and spread of NIS in the marine environment. The input levels, frequency of occurrence, spatial extent, and exposure to different human activities all collectively contribute to the extent to which NIS pressures are exerted on pelagic habitats, benthic habitats, fish, marine birds and marine mammals. NIS can out-compete and prey on native species, resulting in declines in their abundance. Impacts are associated with the introduction of parasites and pathogens; NIS-induced changes in ecosystem functioning (e.g. food-web structure changes); changes in species assemblages and biotic homogenization; and NIS-induced changes in the provision of ecosystem services. To undertake a full quantitative analysis of cumulative effects requires consideration of the exposure pathways and ecological impacts. Further analyses and evidence of ecological impacts are required in order to progress the assessment of cumulative effects.
NIS can also combine with other pressures to affect marine species and habitats collectively. The assessment of cumulative effects is considered in these biodiversity thematic assessments: