How Human-Made Dams Are Changing Earth’s Poles: Insights from Scientists

Recent research reveals a surprising consequence of human activity: the construction of dams has shifted the Earth’s poles. Over the past 200 years, we’ve built nearly 7,000 large dams. This has altered the planet’s mass distribution and nudged the poles about three feet (one meter) from their original spots. Interestingly, this also led to a drop in global sea levels by roughly 0.83 inches (21 millimeters), as published in Geophysical Research Letters.

Why does this happen? Earth has a solid crust that encases a molten interior. When mass shifts—like when we create reservoirs behind dams—the outer rock layer wobbles slightly. This allows different areas on the surface to align over the planet’s rotational axis, a phenomenon known as true polar wander.

Natasha Valencic, a Harvard graduate student and lead author of the study, explains, “When we trap water behind dams, we not only remove it from the oceans, but also shift mass around the planet.” This change can seem small, but it has significant implications for understanding sea level changes.

The research team used a global database of dams to examine their locations, sizes, and impacts. From 1835 to 2011, approximately 6,862 large dams were built, which together hold enough water to fill the Grand Canyon twice. The study shows that the first wave of dam construction, primarily in North America and Europe, caused the North Pole to shift about 8 inches (25 centimeters) toward the east. A second wave of building, mostly occurring in Asia and East Africa, shifted the pole another 22 inches (57 centimeters) further west.

This is a critical insight for scientists. During the 20th century, global sea levels have risen between 4.7 to 6.7 inches (12 to 17 centimeters). Remarkably, about a quarter of that volume was stored in dams. Valencic emphasizes, “We need to consider how the placement of dams affects sea level rise geometry. These shifts can be large and have significant impacts.”

This research ties into a growing understanding of how human activities reshape our planet. With climate change continuing to threaten coastal regions, it’s essential to consider how our infrastructure impacts natural systems. As patterns of dam construction evolve, the influence on global sea levels will likely be increasingly relevant.

Understanding these dynamics can also help inform future policies. As water management becomes more critical in the face of climate change, knowing how our actions influence Earth’s systems will be vital for sustainable development.

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hydroelectric dams,Planet Earth,Water