Navigating trade-offs between dams and river conservation

Abstract

Non-technical summary There has been a long history of conflicts, studies, and debate over how to both protect rivers and develop them sustainably. With a pause in new developments caused by the global pandemic, anticipated further implementation of the Paris Agreement and high-level global climate and biodiversity meetings in 2021, now is an opportune moment to consider the current trajectory of development and policy options for reconciling dams with freshwater system health. Technical summary We calculate potential loss of free-flowing rivers (FFRs) if proposed hydropower projects are built globally. Over 260,000 km of rivers, including Amazon, Congo, Irrawaddy, and Salween mainstem rivers, would lose free-flowing status if all dams were built. We propose a set of tested and proven solutions to navigate trade-offs associated with river conservation and dam development. These solution pathways are framed within the mitigation hierarchy and include (1) avoidance through either formal river protection or through exploration of alternative development options; (2) minimization of impacts through strategic or system-scale planning or re-regulation of downstream flows; (3) restoration of rivers through dam removal; and (4) mitigation of dam impacts through biodiversity offsets that include restoration and protection of FFRs. A series of examples illustrate how avoiding or reducing impacts on rivers is possible – particularly when implemented at a system scale – and can be achieved while maintaining or expanding benefits for climate resilience, water, food, and energy security. Social media summary Policy solutions and development pathways exist to navigate trade-offs to meet climate resilience, water, food, and energy security goals while safeguarding FFRs.

A global agenda for advancing freshwater biodiversity research

“…This includes environmentally and ecologically compatible dam schemes to minimise negative impacts. Given the current global surge in hydropower dam construction and planning, and acknowledging the wealth of literature available on the impacts of dams on freshwaters (Reid et al, 2019; Thieme et al, 2021; Zarfl et al, 2019), it is fundamental to implement evidence‐based guidelines for improving dam building and operation to preserve ecological connectivity. As a broad guiding principle, evidence‐based strategies need to be implemented to enhance blue infrastructure and preserve the associated ecosystem services provided by freshwater biodiversity.…”

A riverine biodiversity hotspot in northern Myanmar supports three new and narrowly endemic freshwater mussel species

“…These results indicate that the country still harbours a diverse native freshwater fauna, which is characterized by a very high level of endemism in certain groups, such as freshwater mussels (Bolotov et al, 2022). This fauna is under severe threat, however, owing to continuing deforestation (Bhagwat et al, 2017; Namkhan et al, 2021), rapid expansion of oil palm plantings (Fitzherbert et al, 2008; Nomura et al, 2019), river damming and pollution (Taft & Evers, 2016; Schmitt et al, 2021; Thieme et al, 2021), mining (Shrestha, Piman & Grünbühel, 2021), and the spread of invasive species (Vikhrev et al, 2017; this study).…”

Resilient rivers and connected marine systems: a review of mutual sustainability opportunities

“…Dams have broad socio-ecological impacts upstream and downstream of their reservoir (Richter et al, 2010), and this issue persists well after the lifespan of the dam has surpassed and restoration is needed (Hansen et al, 2019;Perera et al, 2021) (Bellmore et al, 2019;Tullos et al, 2016). Broader discussion and debate now concern how funds and subsidies are allocated for dams and their anticipated impacts (Hirsch, 2010;Thieme et al, 2021) The Mekong River is one of the world's most important rivers. It is amongst the largest in terms of discharge, it is a "hotspot" for freshwater aquatic biodiversity, and the river basin supports a population of approximately 60 million people, where 70 percent of communities are rural and rice farming and fishing are primary occupations.…”