The economic benefits of dams have been assumed to outweigh the costs, thus providing rationale for construction of dams around the world. However, the development of these structures can be accompanied by negative biophysical, socio-economic, and geopolitical impacts; often through the loss of ecosystem services provided by fully functioning aquatic systems. Moreover, impacts of dams can be involuntarily imposed on marginalized peoples whose livelihoods are dependent on riverine resources. In this review, we examine the impacts of dam projects in regions of the world that are at different stages of development, using the USA, China, and Southeast Asia to represent a development gradient from developed to developing, respectively. Case studies for each region illustrate the environmental and livelihood impacts of dams in each region, while also providing a basis to better understand how environmental degradation is directly related to economic growth. We conclude that a distinct temporal component related to development mediates the relationship between policies and governance mechanisms and the mitigation of environmental and social costs of dams. The role of affected individuals to influence the political will behind dam projects and the importance of environmental advocacy is emphasized as a fundamental approach towards more sustainable development.
SummaryDirect payments to communities or individuals have gained traction as a tool for species conservation; however, few studies have evaluated their effectiveness. From 2010 to 2014, we monitored nests and implemented a direct payment nest protection programme for six sandbar-nesting bird species on the Mekong River, Cambodia, and tested if nest protection improved reproductive success. Nests were guarded by community members; additionally, exclosures were used to protect nests of River Tern Sterna aurantia, the species of highest conservation concern. We investigated factors affecting nest and chick survival, and probability of nest failure due to egg harvest or predation. Nesting later in the season generally resulted in lower nest and chick survival. Nest protection improved survival rates of River Tern nests and chicks, and Small Pratincole Glareola lactea nests. River Tern nest success was 60% for exclosed (and guarded) nests, 29% for guarded (but unexclosed) nests, and 5% for unprotected nests. River Tern fledging success was 82% for exclosed chicks, 40% for chicks that were guarded only, and 2% for unprotected chicks. Small Pratincole nest success was 21% for guarded and 6% for unguarded nests. Egg harvest by humans was lower among protected nests and declined during the study. Nest predation by animals increased during the study despite nest guarding; however, predator exclosures effectively protected nests and chicks. Additional predator control measures could further improve reproductive success of sandbar-nesting birds. Overall, nest protection involving direct payments was highly effective, but required diligent use of nest exclosures, frequent monitoring, and strong community relationships.
Habitat selection occurs at multiple spatial scales and affects demographic processes including reproductive success. Few studies, however, have linked multi-scale habitat selection to reproductive success. We investigated breeding habitat selection at three spatial scales (nest site, nest area and territory), and the consequences of habitat selection on reproductive success of four riverine sandbar-nesting bird species in Cambodia. All species generally selected larger habitat patches, in territories with higher proportions of bare ground substrates, including gravel and dry mud. Individuals generally selected areas with less vegetation; however, at smaller spatial scales, Small Pratincoles (Glareola lactea) and Little Ringed Plovers (Charadrius dubius) used sites with more vegetation. Vegetation generally had a negative effect on reproductive success. For River Terns (Sterna aurantia), nest success was lower in areas with a higher proportion of invasive Mimosa pigra, and chick survival decreased with vegetation height. River Lapwing (Vanellus duvaucelii) nest success decreased with more woody stems, and nest success of Small Pratincoles and Little Ringed Plovers decreased with more herbaceous vegetation. Negative effects of vegetation were likely due to reduced ability of incubating birds to detect predators, or increased cover or foraging efficiency of predators. Finally, proximity to the river channel reduced nest success; nests near the channel had a higher risk of flooding. This is the first study to identify variables associated with habitat selection for all species in this study and to relate habitat use to reproductive success. Results of this study will aid conservation efforts for these regionally threatened species.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.