Characterisation factors for seabed damage: biodiversity impacts within European seas

The marine environment is of great importance for human society through, for example, provision of seafood resources and, increasingly, mineral aggregates. Extraction of such marine resources exerts a pressure on marine... [ view full abstract ]

The marine environment is of great importance for human society through, for example, provision of seafood resources and, increasingly, mineral aggregates. Extraction of such marine resources exerts a pressure on marine ecosystems that can result in biodiversity impacts and reduced ecosystem quality, particularly in benthic habitats. Despite growing utilisation of marine resources by human society, such ecosystem damage is currently neglected from operational life cycle impact assessment (LCIA) methodologies or wrongly assumed negligible. With a desire to improve the comprehensiveness of life cycle assessment (LCA) as a tool for estimating the overall environmental impact of a product or process, we developed a novel marine-focused LCIA model for estimating potential damage-level impacts of seabed damaging activities on benthic biodiversity.

We present novel characterisation factors (CFs) for seabed damage covering European seas, specifically continental shelf areas. Our CFs are spatially differentiated according to seabed substrate type and marine ecoregions of the world (MEoW) and specify potential ecosystem damage in terms of the time-integrated loss of species [PDF.yr]. Our CFs cover both transformation [PDF.yr/m²] and occupation [PDF/m²], and are applicable for activities that cause seabed damage through abrasion (e.g. benthic trawl fisheries) or extraction (e.g. extraction of mineral aggregates) processes.

Our modelling approach is analogous to that developed for the assessment of land use impacts. The overall impact of seabed damage is a function of disturbance characteristics (scale and intensity), initial response of the benthic community, occupation period of the anthropogenic activity and subsequent physical and ecological recovery of the seabed. For impacts of transformation we find that the total impact score is most sensitive to substrate-specific recovery times (including both physical and ecological recovery). We apply median, substrate-specific recovery times from a range of published estimates. Given that ecological recovery requires recolonisation by individuals from intact habitats within dispersal distance of the damaged area, we modified these median substrate-specific recovery times using a habitat rarity index, such that increasing average habitat rarity within a MEoW increases recovery time. We validated our habitat rarity index against the prevalence of ‘critical habitats’ [1] within each MEoW. Critical habitats are defined according to 11 biodiversity features including the distribution of protected areas and habitats supporting threatened or endemic species and ecosystems, and thus also reflect recoverability of damaged seabed areas.  

For the first time we are able to account for biodiversity impacts of seabed damaging activities within LCIA . Due to typically short occupation periods of seabed damaging activities, impacts from transformation are likely to be higher than from occupation. Our preliminary CFs indicate that, within European continental shelf regions, the intensity of impact on benthic biodiversity from seabed transformation due to abrasion and extraction activities is in the range 5 to 30 PDF.yr/m², and is greatest on rock and biogenic reef substrates and lowest on sand substrates.

Reference

1.            Martin, C.S., et al., A global map to aid the identification and screening of critical habitat for marine industries. Marine Policy, 2015. 53(1): p. 45-53.