River dams and the stability of bird communities: A hierarchical Bayesian analysis in a tropical hydroelectric power plant

Abstract

The effects of anthropogenic disturbance upon the stability of wildlife communities depend on the heterogeneity and connectivity of habitat remnants on multiple scales. The number of hydroelectric dams in biodiversity hotspots (Africa, South America and Asia) is growing rapidly. To establish their environmental impact, it is essential to understand the dynamics of wildlife communities before and following the establishment of dams. We evaluated the impacts of the filling of the Serra do Facão hydroelectric reservoir in the São Marcos river, central Brazil, on the bird community. Using data from 1,145 surveys across 20 sampling sites over 8 years, 2 years before and 6 years after the filling of the reservoir, we assessed the resistance, i.e. maintenance close to an equilibrium state during the disturbance, and resilience, i.e. ability to return to the original state following the disturbance, of the bird community. We used spatiotemporal hierarchical Bayesian models to assess the effects of reservoir filling on five community parameters: abundance, richness, phylogenetic diversity, functional diversity and species composition. In the period subsequent to reservoir filling, there was (a) a marked reduction in bird abundance, richness, phylogenetic diversity and functional diversity, and (b) a reduction in the proportion of forest species, coupled with an increase in the proportion of savanna species. Except for bird abundance, none of the other community attributes returned to their original levels, even after 6 years. Our findings indicate that Cerrado bird communities have both low resistance and low resilience to habitat loss associated with the establishment of hydroelectric reservoirs. Synthesis and applications. The environmental costs of hydroelectric dams are still underestimated or neglected in Brazil. A new paradigm in the assessment of their environmental impacts is warranted, incorporating (a) models of spatiotemporal variations based on long‐term monitoring with surveys initiated before disturbances and (b) measures of functional and phylogenetic diversity, such that society can understand the costs and benefits of the establishment of new hydroelectric dams and make informed decisions. Biodiversity loss could be minimized by ensuring the preservation and connectivity of alluvial habitats, capable of maintaining the supply of resources and the functional and phylogenetic attributes of bird communities associated with such habitats.

Drivers of Taxonomic, Phylogenetic, and Functional Beta Diversity of Himalayan Riverine Birds

“…Birds are unlikely to be dispersal limited at the scale at which the analysis has been carried out in the E and the W Himalaya. Although we found limited evidence of the influence of habitat modification on beta diversity patterns in the W but not in the E Himalaya, past studies have documented birds being sensitive to anthropogenic influences (Sinha et al, 2019a;Abreu et al, 2020;Menzies et al, 2021). Finescale information on human disturbance may be able to provide additional insights on human impacts.…”

“…The wide climatic (precipitation), geographic (elevation), and habitat (river width, forest cover) gradient of the Himalayan mountain range contributes to the riverine bird diversity in the region. More than 160 dams have been proposed in the E Himalaya (Vagholikar and Das, 2010), which are likely to permanently alter the riverine systems with significant negative impacts on riverine bird communities as reported elsewhere (Abreu et al, 2020). In the Bhagirathi basin, the construction of the Tehri dam has converted a 75 km stretch of lotic habitat into a lentic habitat (Gaur et al, 2019).…”

Impacts of an Amazonian hydroelectric dam on frog assemblages

“…The temporal change in species composition was accompanied by a reduction in the relative abundance of frogs in most plots, but the number of species increased. The margins of a newly formed reservoir generally do not replicate the same alluvial habitats that previously existed [ 66 , 67 ]. However, there is some evidence that the frog assemblages in the unflooded area were changing even before dam construction, so we cannot be sure whether these changes were caused by the dam filling.…”

“…There is evidence of long-term changes in the structure of the frog assemblages around the Santo Antônio dam, with no indication of return to the initial compositions. Long-term monitoring after project installation with less frequent sampling would allow studies over the longer periods that are often associated with relaxation of biotic communities [ 67 ].…”

Climate Change and the Resilience of Collective Memories

“…Yet, the reliance of the country on its hydraulic capacity continues to grow. The issues revolved mainly around the disruption of the flow of water resources 470 , ecology and natural habitat, 471 the displacement of the surrounding communities, 472 greenhouse gas emissions, 473 and the loss of arable lands. 474 The consequences of the construction of the hydropower plant do not only refer to the migration of human populations but also marine populations.…”