Barcenas-Garcia, A. | Search bioRxiv

bioRxiv2021

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

Background and Research AimsDams impact freshwater ecosystems and biodiversity. Freshwater turtles are at direct and indirect risk due to changes caused by damming including the loss of terrestrial and aquatic nesting habitats, changes to food availability and blocking movement. Effective management of these impacts requires robust evidence in order to gain an understanding of conservation solutions that work. MethodsWe reviewed the global scientific literature that evaluated the impact of dams on freshwater turtles, and carried out additional searches of literature published in seventeen languages for studies evaluating actions to mitigate dam impacts. ResultsThe search produced 47 published articles documenting dam impacts on 30 freshwater turtle species from seven families (Chelidae, Chelydridae, Emydidae, Geoemydidae, Kinosternidae, Podocnemididae and Trionychidae) in 13 countries. Few studies were found from Europe and Asia and none from Africa. Most studies were from temperate latitudes, where studies focused more on adults and less threatened species compared with tropical latitudes. More than half of the studies (57%, n = 27) suggested actions to help mitigate dam impacts. Yet, only five studies (three temperate and two tropical) documented the effect of interventions (dam removal, flow management, artificial pond maintenance and community-based action). ConclusionThese findings demonstrate a serious lack of documented evidence evaluating mitigation actions for dam impacts on freshwater turtles. Implications for Conservation: This lack of evidence reinforces the importance of strengthening and maintaining robust long-term studies needed to develop effective and adaptive conservation actions for this group of threatened vertebrates particularly in tropical regions.

zoology↗

bioRxiv2021

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

O_LIConstruction of hydropower dams is associated with negative impacts on biodiversity, yet there remains a lack of robust scientific evidence documenting the magnitude of these impacts particularly across highly biodiverse tropical waterways. Hydropower expansion is an increasing threat to the Endangered yellow-spotted river turtle (Podocnemis unifilis) across its tropical South American range. C_LIO_LIYellow-spotted river turtle nesting areas were monitored as an indicator of dry season river level changes following run-of-river dam reservoir filling. A Before-After-Control-Impact (BACI) study design was used with multi-year field campaigns monitoring turtle nesting areas upstream of the dam. C_LIO_LIThe cause and extent of changes in nesting areas were established using Generalized Additive Models. Nesting area density was evaluated in relation to: time (before versus after), treatment (control versus impact), time treatment interaction (BACI), distance to the dam and precipitation. The extent of changes was examined by comparing the proportion of nesting areas remaining during four years after reservoir filling. C_LIO_LIDam construction generated an immediate and apparently permanent dry season river level rise that extended more than 20 km beyond impact assessment limits. On average the density of nesting areas declined 69% (from 0.48 to 0.15 per km) across 33 km of river directly impacted by the dam. This loss was reflected in a significant BACI interaction. Nesting area density was not explained by seasonal precipitation. C_LIO_LIStandardized monitoring of freshwater turtle nesting areas provided an effective means to quantify impacts of hydropower developments across biodiverse yet rapidly changing waterways. The negative impacts documented in this study should be preventable by mitigation actions including habitat creation and dry season flow regulation. Such measures would also likely benefit multiple species elsewhere in tropical rivers increasingly impacted by run-of-river dams. C_LI

zoology↗