Beyond harm’s reach? Submersion of river turtle nesting areas and implications for restoration actions after Amazon hydropower development

Abstract

The global expansion of energy demands combined with abundant rainfall, large water volumes and high flow in tropical rivers have led to an unprecedented expansion of dam constructions in the Amazon. This expansion generates an urgent need for refined approaches to river management; specifically a move away from decision-making governed by overly generalized guidelines. For the first time we quantify direct impacts of hydropower reservoir establishment on an Amazon fresh water turtle. We conducted surveys along 150 km of rivers upstream of a new dam construction during the low water months that correspond to the nesting season of Podocnemis unifilis in the study area. Comparison of nest-areas before (2011, 2015) and after (2016) reservoir filling show that reservoir impacts extend 13% beyond legally defined limits. The submerged nesting areas accounted for a total of 3.8 ha of nesting habitat that was inundated as a direct result of the reservoir filling in 2016. Our findings highlight limitations in the development and implementation of existing Brazilian environmental impact assessment process. We also propose potential ways to mitigate the negative impacts of dams on freshwater turtles and the Amazonian freshwater ecosystems they inhabit.

Co‐management of culturally important species: A tool to promote biodiversity conservation and human well‐being

“…However, high levels of illegal harvesting continued in the absence of adequate enforcement (Fachín‐Terán, Vogt, & Thorbjarnarson, ; Kemenes & Pezzuti, ; Peñaloza, Hernández, & Espín, ). The situation was aggravated by the construction of highways and large hydroelectric dams directly impacting the nesting beaches (Alho, ; Norris, Michalski, & Gibbs, ; Smith, ). Faced with the depletion of Podocnemis spp.…”

Nest removal by humans creates an evolutionary trap for Amazonian freshwater turtles

“…Nest searching was conducted between October and December 2017 during the nesting season of P. unifilis in the region (Norris, Michalski & Gibbs, 2018b;Norris et al, 2018a). Nesting areas were identified as areas of >5 m 2 of exposed sand and/or fine gravel and sufficiently raised above the river level not to be waterlogged at a depth of 15 cm, a representative depth that females dig when nesting [Supporting Information Figure S1, (Escalona et al, 2009;Pignati et al, 2013;Norris et al, 2018a)]. In all nesting areas, our search for nest sites was done together with the local residents with over 30 years of knowledge on nesting areas (Norris et al, 2018a).…”

“…Islands are geographically isolated from the forest, which may reduce natural predation risks (Moll & Moll, 2004;Ferreira & Castro, 2010). Nesting area insularity is particularly important for prioritizing conservation actions for P. unifilis across the Amazon, for example, for restoration of potential nesting areas after submersion due to river flow management and reservoir formation following the construction of new hydroelectric power plants (Norris et al, 2018a).…”

Peer Review #2 of "Community involvement works where enforcement fails: conservation success through community-based management of Amazon river turtle nests (v0.3)"

“…To quantify levels of nest harvesting a series of nesting area surveys (Norris et al 2018) were conducted between September and December in all study years. These months correspond to low water and include the complete nesting and first half of the hatching season in the study area (D. Norris pers.…”

“…Nesting data from 2011 were obtained from a previous study (Arraes 2012). In 2015, 2016, and 2017 we then repeated the methodologies applied in 2011, as briefly summarized here, with full details available in Norris et al (2018). To locate river turtle nests we conducted monthly (interval of 20 -30 days between visits) surveys of all potential nesting areas including river banks and islands along the 33 km section by navigating along the river in a motorized boat at a constant speed (ca.…”