Impacts of a large hydroelectric dam on the Madeira River (Brazil) on floodplain avifauna

Abstract

Hydroelectric dams represent an important threat to seasonally flooded environments in the Amazon basin. We aimed to evaluate how a dam in the Madeira River, one of the largest tributaries of the Amazonas River, affected floodplain avifauna. Bird occurrence was recorded through simultaneous passive acoustic monitoring in early successional vegetation and floodplain forest downstream from the dam and upstream in sites impacted by permanent flooding after dam reservoir filling. Species were identified through manual inspection and semi-automated classification of the recordings. To assess the similarity in vegetation between downstream and upstream sites, we used Landsat TM/ETM+ composite images from before (2009-2011) and after (2016-2018) reservoir filling. Downstream and upstream floodplain forest sites were similar before, but not after dam construction. Early successional vegetation sites were already different before dam construction. We recorded 195 bird species. While species richness did not differ between upstream and downstream sites, species composition differed significantly. Ten species were indicators of early successional vegetation upstream, and four downstream. Ten species were indicators of floodplain forest upstream, and 31 downstream. Seven of 24 floodplain specialist species were detected by the semi-automated classification only upstream. While we found some bird species characteristic of early successional vegetation in the upstream sites, we did not find most species characteristic of tall floodplain forest. Predominantly carnivorous, insectivorous, and nectarivorous species appear to have been replaced by generalist and widely distributed species.

Late Pleistocene landscape changes and habitat specialization as promoters of population genomic divergence in Amazonian floodplain birds

“…In addition, the different responses of population connectivity to historical environmental change also offer insights into current threats faced by Amazonian floodplains. For instance, the Santo Antonio and Jirau hydroelectric dams on the white‐water Madeira River, one of the largest tributaries of the Amazon River, have rapidly changed habitats used by floodplain birds (Melo et al, 2021). This is an important aspect of conservation, since rapid anthropogenic changes can reduce connectivity among populations, increasing the risk of local extinction by isolating small populations.…”

The impact of a run‐of‐the‐river hydroelectric dam on a non‐volant small‐mammal assemblage in Brazilian Amazonia

“…Unlike what has been reported for other biological groups (bats: Bobrowiec & Tavares, 2017, Bobrowiec et al, 2021; birds: Melo et al, 2021; palm trees: Santos et al, 2020; and frogs: Dayrell et al, 2021), our study showed that the assemblages of non‐volant small mammals are not likely to be immediately threatened regionally by the construction of a run‐of‐the‐river dam and the filling to its associated reservoir. Variations in vegetation structure and edaphic characteristics present in the areas that will be submerged will be preserved in some of the unflooded areas, and this may help maintain the original species composition of small non‐volant mammals after the dam is filled.…”

“…construction begins can provide information on which species will be affected, whether the assemblages from the flooded areas can move to adjacent dry areas, how changes in groundwater levels influence changes in vegetation as well as serve as a model to assess temporal changes in the regional biota (Bobrowiec et al, 2021;Dayrell et al, 2021;Melo et al, 2021).…”

“…Predictive studies based on data collected before the filling of the hydroelectric reservoir are rare, so most impact assessments do not have enough information to assess the real state of biological communities before the installation of the hydroelectric plant (Athayde et al, 2019; Avenant & Kuyler, 2002; Granjon et al, 1996). Studies carried out before dam construction begins can provide information on which species will be affected, whether the assemblages from the flooded areas can move to adjacent dry areas, how changes in groundwater levels influence changes in vegetation as well as serve as a model to assess temporal changes in the regional biota (Bobrowiec et al, 2021; Dayrell et al, 2021; Melo et al, 2021).…”

The challenges and potential of geogenomics for biogeography and conservation in Amazonia

“…Lack of detailed information on the natural history of species whose distributions and population dynamics we are trying to infer in time and space presents another challenge. Even the basic distinction between seasonally flooded versus upland (never flooded) habitats is often not clear in threat assessments and deforestation mapping, even though these distinct habitat types and their associated biota have very different spatial distribution, respond differently to climatic extremes, and recover differently from fires (Flores et al, 2017; Melo et al, 2021). For example, species that today occur in upland, non‐flooded terra firme habitats may have relied historically on extensive habitat available throughout Amazonia to track appropriate climatic conditions within the mosaic of distinct upland forest patches.…”