Millimeters That Matter: The Sea Level Rise Threshold Coastal Wetlands Can't Survive

How To Protect The Ocean · Sep 17, 2026 · 10m · transcript

Sea level rise. It's a phrase everyone's supposed to be afraid of, and almost nobody can picture. A couple of millimeters a year sounds too small to matter, until you find out coastal wetlands have an exact, measured speed limit for how fast they can keep up, and the ocean is closing in on it.

Marshes and mangroves have kept pace with a rising sea for thousands of years by building their own soil upward, layer by layer, as plants grow, die, and get buried in place. That strategy has a hard limit. Peer-reviewed research puts it at roughly 6.1 millimeters of sea level rise a year, the point…