Source: https://www.sciencealert.com/humanity-has-dammed-so-much-water-its-shifted-earths-magnetic-poles

Recent shifts in Earth’s magnetic field have human fingerprints all over them. While it is normal for our planet’s magnetic poles to sporadically wander, new research shows we’ve now amassed enough water behind dam walls to account for at least some of the current movements.

Harvard University geophysicist Natasha Valencic and colleagues calculated that the masses concentrated in just under 7,000 of Earth’s biggest dams have knocked the crust’s axis of rotation off kilter by around one meter (three feet) relative to the dynamo that drives the magnetic fields beneath the crust.