California’s Coastal Dunes Are Vanishing. Over 60% Have Disappeared Since 1850

The loss is accelerating and leaving entire ecosystems vulenrable.

30 Jun 2026, 16:28 by Saima May Sidik · ZME Science

California has lost about 60% of its coastal sand dunes since the mid-1800s, according to a new study. That means one of the state’s most important natural coastal defenses has been shrinking for more than a century and a half.

How bad is it?

Dunes are more than pretty piles of sand. They absorb wave energy, reduce flooding, and help shield coastal communities from storms and rising seas. They also provide habitat for plants, insects, birds, and small mammals, including federally protected species such as the least tern and the western snowy plover.

But dunes are also easy to erase. They often sit on flat, sandy, highly desirable land near the ocean — exactly the kind of land people like to build on.

To protect dunes, scientists need a comprehensive picture of where these ecosystems are located, but existing datasets tend to be incomplete. To get the full picture, Baxter et al. compared historical maps to the current locations of sand dunes to see how their extent and distribution have evolved over time. To find the current locations of sand dunes, the researchers used aerial photographs and lidar data, which they analyzed using a combination of machine learning and manual identification.

California has lost about 442 square kilometers of dunes since the 1850s, which represents about a 60% drop, the researchers found. Dunes that remain have reduced connectivity, making them less favorable as habitat for some species, including federally protected birds like least terns and western snowy plovers. In most cases, those losses occurred because dunes were replaced by human infrastructure such as highways and housing developments. Erosion eliminated others, and invasive grasses further damaged dunes by outcompeting native grasses and hampering restoration efforts.

Some silver linings

In some limited cases, dunes actually expanded, usually because of additional sand accumulation on their seaward sides. The researchers estimate that California gained 15.2 square kilometers of new dunes in this way since the 1850s.

But these small gains are not nearly enough to compensate for the large losses sand dunes have experienced over the past 200 years. With winter storms intensifying because of climate change, those losses could soon become problematic for coastal residents, who depend on sand dunes for protection from the sea.

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That matters because climate change is raising the stakes. Sea level rise is already putting pressure on coastal ecosystems, and stronger winter storms could make dune loss even more dangerous for people living near the shore. Without healthy dunes, communities may face more erosion, flooding, and storm damage.

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The study suggests that protecting what remains — and restoring dunes where possible — could give California a better natural buffer against the sea.

The study was published in Earth’s Future, https://doi.org/10.1029/2025EF007790, 2026.