Over two billion acres have been seized from Native Americans through broken treaties, land allotment, and forced removal since settlers first arrived in North America. Other understudied causes of Native land loss, like man-made floods, push that number even further: According to a new study published in Environmental Research Letters, the amount of tribal lands lost due to flooding from dams amounts to over a million acres, exceeding the sizes of Great Smokey Mountains National Park, Grand Teton National Park, and Rocky Mountain National Park combined.

“The consequences of dam-induced land loss are far-reaching. The disruption of aquatic and terrestrial ecosystems not only devastates natural resources but also destroys culturally significant sites," said Heather Randell, Assistant Professor of Rural Sociology and Demography at Pennsylvania State University, and one of the study's authors. "The impact on local communities’ livelihoods and displacement from their ancestral lands is equally severe.”

The researchers compared data on the boundaries of federal Indian reservations with the placement of over 7,900 dams, and estimated that 424 dams have submerged over 1.3 million acres of tribal land in the continental United States. They found that most dams flooded river valleys, which tend to be the most densely populated lands on Native American reservations for their "economic, social, and cultural" value. Aquatic ecosystems that Native tribes rely on, like fisheries and wild rice beds, have been disrupted by the construction of dams.

These findings come at a critical time when the Biden administration has made infrastructure a primary focus. At least $800 million was allocated for dam removal in 2021, and another act introduced the same year could provide an additional $7.5 billion. The researchers suggest that dams which negatively impact tribal lands should be prioritized for removal, and that tribes should be directly involved throughout the process. In cases where dam removal is not feasible, tribal ownership and funding for repairs should be granted.

Randall urges lawmakers to consider the U.S. government's obligations to Native Americans as infrastructure projects are undertaken: “This is an opportunity to address historical land dispossession and to respect the sovereignty and rights of Indigenous communities."