Assessing Ecological and Social Dimensions of Success in a Community-based Sustainable Harvest Program

Gibbs

et al. 2022

Aquatic Conservation

Hydropower dams are associated with adverse impacts on biodiversity, yet there remains a lack of robust scientific evidence documenting the magnitude of these impacts, particularly across highly biodiverse tropical waterways. Aquatic and semi‐aquatic vertebrates are disproportionately affected by human changes to aquatic environments and hydropower expansion is an increasing threat to the Endangered yellow‐spotted river turtle (Podocnemis unifilis) across its tropical South American range. Yellow‐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. The cause and extent of changes in nesting areas were established using generalized additive models. Nesting area density was evaluated in relation to time (before vs. after), treatment (control vs. impact), time–treatment interaction (BACI), distance to the dam and precipitation. The extent of changes was examined by comparing the remaining proportion of nesting areas after reservoir filling. Dam 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 by 69% (from 0.48 to 0.15 per km) across 33 km of river directly affected by the dam. This loss was reflected in a significant BACI interaction. Nesting area density was not explained by seasonal precipitation. Monitoring of freshwater turtle nesting areas provided an effective means to quantify hydropower dam impacts across biodiverse yet rapidly changing waterways. The adverse impacts documented in this study should be preventable by mitigation actions including habitat creation and dry season flow regulation. Such measures are also likely to benefit multiple sandbar‐nesting species (including turtles, crocodiles and birds) in tropical rivers increasingly influenced by run‐of‐river dams.

Section: Discussionmentioning

confidence: 99%

“…In addition, these actions bring conservation co‐benefits for other species: for example, migratory waterfowl, which also use the turtles’ nesting habitat (Campos‐Silva et al, 2021). Similarly, local communities can also obtain economic and food benefits (Harju, Sirén & Salo, 2018; Rivera et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Amazonian run‐of‐river dam reservoir impacts underestimated: Evidence from a before–after control–impact study of freshwater turtle nesting areas

Gibbs

et al. 2022

Aquatic Conservation

“…In addition, these actions bring conservation co-benefits for other species, for example migratory waterfowl, which also use the turtles' nesting habitat (Campos-Silva et al, 2021). Similarly, local communities can also obtain economic and food benefits (Harju, Sirén, & Salo, 2018;Rivera et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…Continuous and standardized monitoring of nesting-areas can be implemented and strengthened through the establishment of community management programs (Harju, Sirén, & Salo, 2018;Rivera et al, 2021). Several studies have shown the benefits of this type of management focused on the conservation of nesting-areas and maintaining the recruitment of turtle populations (Campos-Silva et al, 2018;Norris et al, 2019).…”

Section: Conservation Recommendationsmentioning

confidence: 99%

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

Gibbs

et al. 2021

Preprint

1. Although the construction of hydropower dams is widely assumed to generate myriad negative impacts on biodiversity 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. 2. 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 established with multi-year field campaigns monitoring turtle nesting-areas along 66 km of river upstream of the dam, separated into 33 km control and impact zones. 3. The cause and extent of changes in nesting-areas was established using Generalized Additive Models. Nesting-area density was examined in relation to four variables: Before-After, Control-Impact, distance to the dam and precipitation. The extent of changes was examined by comparing the proportion of nesting-areas remaining in subzones during the four years after reservoir filling. 4. Comparison of the proportion of nesting-areas remaining after dam construction showed that a permanent dry season river level rise 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. The variation in nesting-areas was not explained by seasonal precipitation, whilst nesting-area density increased significantly further away from the dam. 5. Standardized 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 should be preventable by mitigation actions including habitat restoration and dry season flow regulation. Such measures are also likely to benefit multiple species in highly diverse Amazonian rivers increasingly impacted by run-of-river dams.

“…Actions may also include rescue activities such as that which occurred in the eastern Brazilian Amazon, where community based actions contributed to the rescue of 926 eggs, 65 premature hatchlings and the release of 599 hatchlings of P. unifilis during the flooding of nests by rising water levels (Norris et al, 2020). However, community participation in any conservation project requires that the communities be taken into consideration when creating plans or management projects (Campos-Silva et al, 2018; Rivera et al, 2021), procuring sources of economic income, as well as providing the necessary inputs for project development so that they are not abandoned due to lack of resources (Norris et al, 2018b; Stone et al, 2014).…”

Section: Discussionmentioning

confidence: 99%

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

Morgan

et al. 2021

Preprint

Dams create many impacts on 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 and feeding habitats, changes to resource availability and reduced dispersal. We 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 the impact of dams. The search produced 43 published articles documenting dam impacts on 29 freshwater turtle species from seven families (Chelidae, Chelydridae, Emydidae, Geoemydidae, Kinosternidae, Podocnemididae and Trionychidae) in 13 countries. More than a third of studies (41.9%, n = 18) focused on nine North American species of the Emydidae. Few studies were found from Europe and Asia and none from Africa. The number of studies, life-history stage studied and threat status differed significantly between temperate and tropical latitudes. Most studies were from temperate latitudes, where studies focused more on adults and less threatened species compared with tropical latitudes. Studies evaluated dam impacts as barriers and changes to water flow and quality, but no studies were found that assessed turtles and changes to land cover or mercury caused by dams. More than half of the studies (59%, n = 24) suggested actions to help mitigate dam impacts. Yet, only four studies on three temperate and one tropical species documented the effect of interventions (dam removal, flow management, artificial pond maintenance and community-based action). These findings demonstrate a lack of documented evidence evaluating dam impacts on freshwater turtles particularly in tropical regions. This lack of evidence reinforces the importance of strengthening and maintaining robust long-term studies of freshwater turtles needed to develop effective conservation actions for this group of vertebrates.