Characterizing dam fragmentation impacts on freshwater fish within life cycle impact assessment

Damming-induced fragmentation hinders crucial fish migration for feeding and spawning and alters habitat quality. However, the Life Cycle Assessment (LCA) framework lacks a model to quantify the impacts of freshwater habitat fragmentation. Our proposed methodology addresses this gap by developing characterization factors (CFs) with global coverage for the isolation risk of 7369 freshwater fish species. We use a macroecological range size-body size relationship to determine species' Minimum Viable Range Size (MVRS) and apply it to assess range fragmentation caused by 31,870 dams. To consider multipurpose reservoirs, we allocate the quantified impact in Potentially Disappeared Fraction of species (PDF) based on a ranking approach. The CFs express global quantified impact and range from 0 to 2.39·10⁻¹² PDF·yr·m⁻³ for hydropower for 524 basins, and from 0 to 3.17·10⁻⁰⁷ PDF·yr·m⁻³ for irrigation for 1355 basins worldwide. We calculate a weighted mean from the CFs per basin to obtain a global CF. This CF is 3.89·10⁻¹⁵ PDF·yr·m⁻³ (± 2.01·10⁻¹⁴ weighted standard deviation) for hydropower and 7.66·10⁻¹⁴ PDF·yr·m⁻³ (± 2.27·10⁻¹² weighted standard deviation) for irrigation. Applying the hydropower and irrigation CFs to a global case study for the operation of a hydropower plant and the production of basmati rice shows that the impact scores for fragmentation exceed those for land inundation and global warming but not for water consumption. In the case of Norway, the hydropower-induced fragmentation impact scores are the highest. This shows the importance of including freshwater fragmentation in decision-making tools such as LCA.