Coral reef decline driven by climate change could cost Hawaiʻi residents between $1.8 billion and $3 billion in lost reef-related activities by 2100, according to a new study published in Ecological Economics. The research projects these burdens will not fall equally, with lower-income and disadvantaged communities in the state facing disproportionate impacts.
The study was led by researchers at the University of Hawaiʻi at Mānoa's College of Tropical Agriculture and Human Resilience (CTAHR), alongside scientists from the Norwegian University of Life Sciences and the University of Trento. It is one of the first studies to combine detailed ecological models with community-level economic data across the state.
"Coral reefs are foundational to life in Hawaiʻi culturally, ecologically and economically," said lead author Ashley Lowe Mackenzie, an affiliated faculty member in the CTAHR Department of Natural Resources and Environmental Management (NREM). "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."
Mapping future losses
The research team used a sophisticated biophysical simulation called the Atlantis ecosystem model to project how coral cover will change across nearshore reef systems through the year 2100. They tested three different climate pathways representing low, mid-range and high global emissions scenarios.
By connecting these ecological shifts with a recreation demand model, they mapped potential economic losses for residents at a precise 1-kilometer resolution. Because the figures only capture local recreational use—such as swimming, snorkeling and diving—the authors emphasize that the $1.8 billion to $3 billion estimate represents a lower end of total economic damage.
Key findings include:
- The earliest and most severe losses are projected along the leeward (west and south) coasts of Hawaiʻi Island and Maui.
- Recreational losses are expected to spread northward to Oʻahu by mid-century.
- Under a high-emissions climate scenario, nearshore reefs face a near-total collapse by 2100. Under a low-emissions scenario, some windward (east and north) coastlines show signs of partial recovery late in the century.
Disproportionate impacts on local communities
Using the U.S. Environmental Protection Agency's environmental justice tool (EJScreen), the researchers discovered that disadvantaged communities often face higher per-person welfare losses. Traditional economic methods usually project lower monetary losses for lower-income groups, making this finding particularly striking. The data indicate that vulnerable communities are disproportionately exposed to the specific areas experiencing 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 Hawaiʻi," said Brian Neilson, administrator of the Hawaiʻi Division of Aquatic Resources. "Reef-based recreation is deeply tied to traditions of fishing, gathering, and caring for our nearshore waters."
A call for local action
The findings connect directly to local state-led efforts such as Hawaiʻi's Holomua Marine Initiative, which works with communities and Indigenous knowledge holders to design site-specific reef management.
"The magnitude of those potential losses should be a wake-up call to take action now to protect our nearshore environment," said senior author Kirsten L.L. Oleson, NREM professor. "Our lab's research suggests that a lot can be accomplished through local action, particularly by reducing land-based pollution and over-harvesting."
The research was supported by NOAA's Ocean Acidification Program.
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