Proposals to build more than 150 hydroelectric dams on Andean tributaries of the Amazon River could have catastrophic ecological impacts, causing the first major breaks between the tributaries and the Amazon and leading to widespread forest loss, according to a study published today in the scientific journal PLoS ONE.

The study by researchers at the environmental advocacy group Save America’s Forests, the Center for International Environmental Law, and North Carolina State University found that 47 percent of dams planned for Amazon tributaries in Bolivia, Colombia, Ecuador and Peru would have a high environmental impact, suggesting the need for additional evaluation and increased regional planning.

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Examples of high-impact dams, according to the study,