Trading-off fish biodiversity, food security, and hydropower in the Mekong River Basin

TLDR

The Mekong River Basin, the world’s largest inland fishery, is experiencing extensive hydropower development that threatens fish migration by blocking critical routes between downstream floodplains and upstream tributaries. This study estimates fish biomass and biodiversity losses across multiple damming scenarios using a simple ecological model of fish migration. The framework quantifies trade‑offs among dam locations, power output, and impacts on fish resources. Our analysis shows that completing 78 tributary dams would catastrophically reduce fish productivity and biodiversity, prompting a call to reassess several projects and establish a new regional agreement on tributary development.

Abstract

The Mekong River Basin, site of the biggest inland fishery in the world, is undergoing massive hydropower development. Planned dams will block critical fish migration routes between the river's downstream floodplains and upstream tributaries. Here we estimate fish biomass and biodiversity losses in numerous damming scenarios using a simple ecological model of fish migration. Our framework allows detailing trade-offs between dam locations, power production, and impacts on fish resources. We find that the completion of 78 dams on tributaries, which have not previously been subject to strategic analysis, would have catastrophic impacts on fish productivity and biodiversity. Our results argue for reassessment of several dams planned, and call for a new regional agreement on tributary development of the Mekong River Basin.