Leeward Maui is among the areas expected to see the earliest and most severe recreational losses from climate-driven coral reef decline, according to a new study that estimates Hawaii residents could lose between $1.8 billion and $3 billion in reef-related recreation by 2100.

The study, published in the journal Ecological Economics, was led by researchers at the University of Hawaii at Manoa’s College of Tropical Agriculture and Human Resilience.

Researchers found that the impacts would not fall equally, as lower-income and disadvantaged communities are expected to face disproportionate impacts from the loss of reef-related activities.

“Coral reefs are foundational to life in Hawaiʻi culturally, ecologically and economically,” said lead author Ashley Lowe Mackenzie, an affiliated faculty member in the college’s Department of Natural Resources and Environmental Management. “Our work makes visible something that is often invisible in policy conversations by valuing real welfare losses that residents will experience as these ecosystems degrade.”

For the study, scientists from the Norwegian University of Life Sciences and the University of Trento used ecological modeling to project changes in coral cover across nearshore reef systems through 2100 under low, mid-range and high global emissions scenarios. They then connected those projections with a recreation demand model to map potential economic losses for residents.

The estimate includes only local recreational use, such as swimming, snorkeling and diving, meaning the projected $1.8 billion to $3 billion in losses represents a lower estimate of the total economic damage, researchers said.

The study found that the earliest and most severe losses are projected along the leeward coasts of Maui and Hawaii Island.

Recreational losses are expected to spread northward to Oahu by mid-century. Under a high-emissions scenario, nearshore reefs face a near-total collapse by 2100, while a low-emissions scenario showed some windward coastlines with signs of partial recovery late in the century.

Researchers also found that disadvantaged communities often face higher per-person welfare losses because they are disproportionately exposed to areas expected to see the steepest reef declines.

“This study puts numbers to what our communities have long understood — that losing our reefs means losing the recreational opportunities, cultural practices and quality of life that define what it means to live in Hawaii,” said Brian Neilson, administrator of the Hawaii Division of Aquatic Resources. “Reef-based recreation is deeply tied to traditions of fishing, gathering, and caring for our nearshore waters.”

Senior author Kirsten L.L. Oleson, a professor in the Department of Natural Resources and Environmental Management, said the findings point to the need for local action.

“The magnitude of those potential losses should be a wake-up call to take action now to protect our nearshore environment,” Oleson said. “Our lab’s research suggests that a lot can be accomplished through local action, particularly by reducing land-based pollution and over-harvesting.”