Collaborative study about complex shapes of reefs helps guide cutting-edge restoration

Collaborative research from the University of Hawaiʻi at Mānoa and Macquarie University in Sydney, Australia, reveals that the complex shapes of reefs are not random but are built by “master architects.”

From the coral reefs of the tropics to the oyster reefs of temperate estuaries, the complex shapes of these diverse ecosystems follow geometric rules that maximize survival, according to a study published in “Nature.”

Research from the Hawaiʻi Institute of Marine Biology and Macquarie University offers a proven guide for reviving damaged marine habitats and protecting the vital seafood sources that communities depend on.

According to Joshua Madin, a Hawaiʻi Institute of Marine Biology research professor and senior author of the study, the work shows that there are universal architectural rules for reef persistence.

“Nature has already solved the design problem. Our job is to read that blueprint and scale it up to help reefs grow faster and survive longer,” Madin said.

Using high-resolution 3D mapping and field experiments in Australia, the team engineered concrete structures spanning a wide range of surface complexities.

The team discovered that simple structures left juvenile oysters exposed to predators, while overly complex structures offered diminishing returns. Survival peaked at a specific, optimal combination of height and fractal dimension, which is exactly the geometry found in thriving natural reefs.

“Reefs are not just piles of skeletons or shells,” said Juan Esquivel-Muelbert, the study’s lead author from Macquarie University. “They are finely tuned three-dimensional machines. Their shape controls who lives, who dies, and how fast the reef grows.”

While the fieldwork focused on oysters, the theoretical principles were developed at the Hawaiʻi Institute of Marine Biology and apply directly to coral reefs.

The study provides the biological validation for cutting-edge restoration work currently underway in Hawaiʻi. The geometric principles utilized are a driving force behind the project, Rapid Resilient Reefs for Coastal Defense (R3D).

Funded by the Defense Advanced Research Projects Agency, the project is deploying immense, geometric reef modules off the coast of Oʻahu to attract coral larvae, protect them from predators, and grow into a thriving coral reef.

“Testing these 3D-printed designs showed we could increase the settlement and survival of corals by 80-fold compared to natural reef surfaces,” Madin said. “By building with the right geometry, we can jump-start the feedback loops that allow reefs to build themselves.”

The study offers a quantitative framework for engineering restoration structures that work across different ecosystems—from salt marshes to coral reefs. With more than half of the worldʻs coral reefs and 85% of oyster reefs lost or severely degraded, the need for effective restoration is urgent.

“If we can capture the right combinations of shape and complexity, we can design restoration structures that function like healthy reefs within a few years,” Madin said. “This is about integrating nature’s own engineering into coastal infrastructure to protect our shorelines and support marine life.”