Think dams only affect local rivers? It turns out they’re quietly nudging Earth’s poles too. A new study reveals that building nearly 7,000 dams since 1835 has redistributed so much water that the North Pole’s position shifted by about 3.7 feet (1.1 meters).

Earth’s outer shell, its crust, can move slightly on the fluid mantle beneath. When dams hold massive reservoirs, they shift the planet’s weight and change how Earth spins. Between 1835 and 1954, dam building in North America and Europe nudged the poles a little eastward. Then, from 1954 to 2011, large-scale construction in Asia and East Africa swung them westward.

All that dammed water has caused global sea levels to drop by nearly an inch. Since dams hold back roughly a quarter of the sea-level increase across the 20th century, scientists say these effects should be included in climate and sea-level forecasts.

While a few feet of polar shift won’t trigger disasters, it highlights how human infrastructure can reshape the planet. As dams continue to hold, and release, massive volumes of water, their impact on Earth’s rotation becomes a part of the bigger climate picture.