Biology subjects

Margni, M.

Publications and source records attributed to Margni, M..

3 recordsLinked to original sources

bioRxiv2021

The impacts of hydropower on freshwater macroinvertebrate richness: A global meta-analysis

Hydroelectric dams and their reservoirs have been suggested to affect freshwater biodiversity. However, studies investigating the consequences of hydroelectric dams and reservoirs on macroinvertebrate richness have reached opposite conclusions. We carried out a meta-analysis devised to elucidate the effects of hydropower dams and their reservoirs on macroinvertebrates richness while accounting for the potential role played by moderators such as biomes, impact types, study designs, sampling seasons and gears. We used a random and mixed effect model, combined with robust variance estimation, to conduct the meta-analysis on 72 pairs of observations (i.e., impacted versus reference) extracted from 17 studies (more than one observation per study). We observed a large range of effect sizes, from very negative to very positive impacts of hydropower. However, according to this meta-analysis, hydropower dams and their reservoirs did not have an overall clear, directional and statistically significant effect on macroinvertebrate richness. We tried to account for the large variability in effect sizes using moderators, but none of the moderators included in the meta-analysis had statistically significant effect. This suggests that some other moderators, which were unavailable for the 17 studies included in this meta-analysis, might be important (e.g., temperature, granulometry, wave disturbance and macrophytes) and that macroinvertebrate richness may be driven by local, smaller scale processes. As new studies become available, it would be interesting to keep enriching this meta-analysis, as well as collecting local habitat variables, to see if we could finally draw statistically significant conclusions about the impacts of hydropower on macroinvertebrate richness.

ecology↗

bioRxiv2019

Changes in freshwater macroinvertebrate richness due to river impoundment in the United States

Whether it is for water supply, flood control or hydropower uses, the transformation of a river into a reservoir can impact freshwater ecosystems and their biodiversity. Using the National Lake Assessment (NLA; 148 reservoirs) and the National Rivers and Streams Assessment (NRSA; 2121 rivers and streams) of the United States Environmental Protection Agency (USEPA), we evaluated the impacts of river impoundment on macroinvertebrate biodiversity at three spatial scales (i.e., reservoir, ecoregion and country scale). We used a space-for-time substitution approach to model the impact of impoundment (i.e., we used rivers and streams as the before-impoundment conditions, and reservoirs as the after-impoundment conditions). We expressed the impact on biodiversity in terms of potentially disappeared fraction of species (PDF) to be used in the life cycle assessment (LCA) framework. To understand the role of regionalization, and some potentially influential variables, on changes in macroinvertebrate richness following impoundment in the United States, we used analyses of variance (ANOVAs) as well as variation partitioning, and developed empirical predictive models. Overall, 26% of macroinvertebrate taxa disappeared following impoundment in the United States, and PDFs followed a longitudinal gradient across ecoregions (i.e., higher PDFs in the western part of the country, lower PDFs in the eastern part). We also observed that large and oligotrophic reservoirs, located in high elevation had high PDFs. This study provides the first empirical PDF values for macroinvertebrates to be used as characterization factors (CFs) by LCA practitioners. We also provide strong support for regionalization and a simple predictive model to be used by LCA modellers.

ecology↗

bioRxiv2019

Empirical characterization factors assessing the effects of hydroelectricity on fish richness across three large biomes

Hydroelectricity is often presented as a clean, reliable, and renewable energy source, but is also recognized for its potential impacts on aquatic ecosystem biodiversity. We used empirical data on change in fish species richness following impoundment to develop Characterisation Factors (CF) and Impact Scores (IS) for hydroelectricity production for use in Life Cycle Assessment (LCA). We used data collected on 89 sampling stations (63 upstream and 26 downstream of a dam) belonging to 27 reservoirs from three biomes (boreal, temperate and tropical). Overall, the impact of hydroelectricity production on fish species richness was significant in the tropics, of smaller amplitude in temperate and minimal in boreal biome, stressing for the need of regionalisation. The impact of hydroelectricity production was also quite consistent across scales (i.e., same directionality and statistical significance across sampling stations, reservoirs and biomes) but was sensitive to the duration of the study (i.e., the period over which data have been collected after impoundment), highlighting the need for a clear understanding of transient situations before reaching steady states. Our CFs and ISs contribute to fill a gap to assist decision makers using LCA to evaluate alternative technologies, such as hydropower, to decarbonize the worldwide economy.\n\nHighlightsO_LIThis paper is the first to develop global and empirically based characterization factors of the impact of hydroelectricity production on aquatic ecosystems biodiversity, to be used in LCA;\nC_LIO_LIThe impact of hydroelectricity production on fish species richness was significant in the tropics, of smaller amplitude in temperate and minimal in boreal biome;\nC_LIO_LIThe impact of hydroelectricity production on fish richness was consistent across scales - same directionality and statistical significance across sampling stations, reservoirs and biomes;\nC_LIO_LIThe impact of hydroelectricity production on fish richness was sensitive to the duration of the study, highlighting the need for a clear understanding of transient situations before reaching steady states in LCA.\nC_LI

ecology↗