Sea-use impact category in life cycle assessment: state of the art and perspectives
Résumé
The present study provides a review on sea-use impacts and how they are handled in life cycle assessments (LCA). It aims at defining the impact pathways for occupation and transformation impacts on marine ecosystems due to human activities (constructions, fishing, aquaculture, navigation). First, a review was performed on human interventions leading to environmental impacts in marine areas and on additional fishery-related impact categories used in LCA of seafood, in order to identify the main methodological deficiencies existing in LCA of seafood products. Second, the sea-use impact category has been defined, by detailing the human interventions leading to impacts on the marine environment and which should be accounted for in LCA. Subsequently, the identification and description of the possible impact pathways linking activities and interventions to impact categories are carried out at endpoint and midpoint levels. This assessment has been based on a review of existing methods of land use, and suggests the use of certain indicators, which could be available for different types of marine activities and ecosystems. This study highlights the needs to account for impacts of human activities due to sea use. Additional indicators have often been added in LCA of seafood, to assess the impacts of seafloor destruction and biomass removal. By extending the scope to other activities than fisheries, many interventions lead to impacts on marine ecosystems: biomass removal and benthic construction, invasive species release, shading, artificial habitat creation, noise, turbidity, and changes in original habitat availability. The impact pathway definition and the identification of the most relevant methods for sea use highlighted the need to assess impacts on ecosystem services (life support functions, global material cycling, and detoxification of pollutants) and on biodiversity as well as biotic resource depletion. A consensus for biotic resource depletion assessment still needs to be found despite recent innovative proposals. For the sea-use impact assessment, methods using species-area relationships, as well as methods focusing on ecosystem services, appear particularly relevant. In a context of strong marine resource overexploitation, and limited marine biodiversity data, the deficiencies in biomass production capability (provisioning services) could be the first stage of sea-use development.