Dams Have Nudged Earth's Poles Over 3 Feet

The world's dams have quietly moved more than just water—their massive reservoirs have actually nudged Earth's poles by feet, according to new research that reveals how human engineering is subtly reshaping our planet. Scientists have long known that large-scale water movement, whether from melting ice or groundwater extraction, can alter the planet's rotational axis. This research, published in Geophysical Research Letters, quantifies the influence of 6,862 dams, showing that the mass of water stored in reservoirs has gradually nudged Earth's poles by more than three feet between 1835 and 2011, per Live Science.

The research team, led by Harvard's Natasha Valencic, used modeling and a global dam database to track this effect, related to the shifting position of Earth's crust relative to the mantle. They found two main phases, beginning with an initial shift from 1835 to 1954 as dams went up in North America and Europe, pulling the North Pole slightly toward Russia, Mongolia, and China. From 1954 through 2011, rapid dam construction in East Africa and Asia put mass on the opposite side of the globe, shifting the pole back toward western North America and the South Pacific. The movement totals about 3.7 feet, though the path is not a straight line.

While this "polar wander" has minimal direct impact on daily life or planetary processes, the researchers say the way dams trap water does affect global sea levels. In fact, water held back by reservoirs has caused sea levels to fall by nearly an inch since the 19th century—enough, the authors argue, that it should be factored into future projections about sea level rise. Water representing roughly a quarter of the 20th century's sea level gain is now sitting in reservoirs, underscoring the outsized influence of human engineering on the planet's delicate balances.