Development of life cycle impact assessment methodologies for impacts on marine ecosystems
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Marine resources are increasingly important for satisfying the needs and wants of the human society. With currently unprecedented human demands on marine resources and space, concerns are rising over observed declines in marine biodiversity. A quantitative understanding of the impact of human activities on the marine environment is essential to help guide actions to minimise anthropogenic biodiversity loss. Life cycle assessment (LCA) is one such tool that can facilitate the targeting of actions to reduce anthropogenic impacts on biodiversity. However, marine impact pathways are currently underrepresented in life cycle impact assessment (LCIA) methodologies. This means that, despite the increasing inclusion of marine resources in global product systems, potential impacts on marine biodiversity are often neglected. To improve the utility of LCA as a decision support tool, the coverage of marine impact pathways needs broadening. This thesis contributes towards broadening the scope of marine impact pathway coverage in LCIA in Chapters 2-4. Chapter 2 addresses the potential for LCIA model development to cover seven predominant anthropogenic drivers of marine biodiversity loss: climate change, ocean acidification, eutrophicationinduced hypoxia, seabed damage, overexploitation of biotic resources, invasive species and marine plastic debris. There is potential to develop impact indicators for all identified drivers, albeit at different levels of impact pathway coverage and variable levels of uncertainty and spatial coverage. Methodological developments for two of the identified anthropogenic drivers of marine biodiversity are included in this thesis: seabed damage and marine plastic debris (Chapters 3 and 4). The LCIA modelling approach for seabed damage, presented in Chapter 3, is globally applicable, parameterized within 17 marine ecoregions in Europe, and includes two perspectives: the singleimpact perspective and the repeated-impact perspective. The resulting characterisation factors (CFs) allow for quantifying indicators of potential ecosystem damage from seabed disturbance in terms of a time-integrated relative species loss. The approach is analogous to the established approach for land use impacts in LCIA, i.e. including both impacts of seabed occupation and impacts of seabed transformation. For impacts of seabed transformation, ecological recovery times are estimated with consideration of spatial-heterogeneity in environmental properties (seabed substrate type, hydrodynamic energy at the seabed and the stock of potential recolonisers). Overall, these CFs improve the potential for including ecosystem damage from seabed disturbance in life cycle assessments. In Chapter 4, a preliminary LCIA approach for capturing the potential entanglement effects of macroplastic debris on marine biodiversity is presented. The results of this preliminary approach highlight the challenge of developing new impact assessment methodologies whilst the underlying impact mechanisms continue to be discovered. This effect factor provides a stepping-stone towards a more robust effect factor modelling approach, and ultimately a complete model for including potential marine ecosystem impacts from plastic waste in LCIA. Finally, as new knowledge and data become available, existing LCIA models should be further developed with a goal of harmonised endpoint metrics. Current endpoint metrics for ecosystem quality are specific to contexts, which differ according to, for example, spatial and temporal scale, taxonomic coverage, and whether the indicator produces a relative or absolute measure of loss. Harmonised endpoint metrics would improve the utility of LCA as a decision support tool by facilitating comparisons across impact categories. Options for working towards harmonised endpoint metrics in the ecosystem quality area of protection are discussed in Chapter 5.