Understanding hydropower impacts on Amazonian wildlife is limited by a lack of robust evidence: results from a systematic review

Abstract

Background and Research Aims: Although hydropower provides energy to fuel economic development across Amazonia, strategies to minimize or mitigate impacts in highly biodiverse Amazonian environments remain unclear. The growing number of operational and planned hydroelectrics requires robust scientific evidence to evaluate impacts of these projects on Amazonian vertebrates. Here we investigated the existing scientific knowledge base documenting impacts of hydropower developments on vertebrates across Brazilian Amazonia. Methods: We reviewed the scientific literature from 1945 to 2020 published in English, Spanish and Portuguese to assess the temporal and spatial patterns in publications and the types of study design adopted as well as scientific evidence presented. Results: A total of 24 published articles documented impacts on fish (n = 20), mammals (n = 3) and freshwater turtles (n = 1). Most study designs (87.5%) lacked appropriate controls and only three studies adopted more robust Before-After-Control-Impact designs. The published evidence did not generally support causal inference with only two studies (8.3%) including appropriate controls and/or confounding variables. Conclusion: Decades of published assessments (54.2% of which were funded by hydropower developers or their subsidiaries) do not appear to have established robust evidence of impacts of hydropower developments on Amazonian vertebrates. This lack of robust evidence could limit the development of effective minimization and mitigation actions for the diverse vertebrate groups impacted by hydroelectrics across Brazilian Amazonia. Implications for Conservation: To avoid misleading inferences there is a need to integrate more robust study designs into impact assessments of hydropower developments in the Brazilian Amazon.

Anthropogenic influences on the distribution of a threatened apex-predator around sustainable-use reserves following hydropower dam installation

“…Thus, even the large coverage of protected areas (22%), which together with indigenous territories protects more than half (52%) of the Amazon rainforest ( Walker et al, 2020 ), is unlikely to offset the negative effects caused by hydropower dams. Although adverse dam effects on Amazonian vertebrates have been widely suggested, there remains a lack of robust evidence to inform development of effective minimization and mitigation actions ( Santos, Michalski & Norris, 2021 ). To our knowledge, here we provide the first study on the effects of a new hydropower dam on a threatened apex-predator (giant otter— Pteronura brasiliensis ) using a before-after control-impact (BACI) study design ( Conner et al, 2016 ).…”

Amazonian run-of-river dam reservoir impacts underestimated: Evidence from a Before-After Control-Impact study of freshwater turtle nesting areas

“…Generating changes not only to biological cycles and species ecological interactions (Latrubesse et al, 2020) but also creating drastic alterations to local communities and cultures (Del Bene, Scheidel, & Temper, 2018;Fearnside, 2018). Whilst negative impacts have been widely suggested, more robust evidence is required to establish the sustainability of the increasing number of dams across Brazilian Amazonia (Rodrigues dos Santos, Michalski, & Norris, 2021;Tundisi et al, 2014).…”

“…Aquatic species, like freshwater turtles are directly impacted by dam construction (Le Duc et al, 2020;Stanford et al, 2020;Tucker, Guarino, & Priest, 2012). Although many studies focus on fishes there are few studies considering the diversity of Amazonian aquatic and semiaquatic vertebrates (Rodrigues dos Santos, Michalski, & Norris, 2021). Turtles represent some of the largest and most threatened freshwater vertebrates (Stanford et al, 2020) and are vulnerable to habitat changes because their life history (Shine & Iverson, 1995) and dependence on environmental factors for embryonic development, which limits the adaptive response for population recruitment against anthropic impacts (Quintana et al, 2019).…”

Impacts of dams on freshwater turtles: a global review to identify conservation solutions

“…Although populations of freshwater vertebrates have declined at more than twice the rate of terrestrial or marine vertebrates (Grooten & Almond, 2018;Tickner et al, 2020), relatively few studies have evaluated the impact of dams on vertebrates (dos Santos et al, 2021;He et al, 2018).…”

“…turtles (Jian et al, 2013;Santoro et al, 2020). Despite the known impacts, there is little available evidence documenting dam mitigation interventions for aquatic fauna such as freshwater turtles (CEE, 2021; dos Santos et al, 2021;Sainsbury et al, 2021;Tickner et al, 2020).…”