From reefs to resilience: researchers in Hawaiʻi combine science and society to tackle ocean acidification
Background image: Researcher diving in coral reef.
Hawaiʻi is changing. Ocean conditions such as ocean warming and ocean acidification threaten Hawaiʻi’s coral reef ecosystems now. As our ocean’s chemistry changes, it becomes harder for coral reefs to build their skeletons, putting these important ecosystems at risk. Coral reefs are an essential part of Hawaiʻi and Hawaiian culture and economy. They form critical habitats for marine life, sustain fisheries, provide coastal protection, and support local economies and communities. Valued at $863 million per year, Hawaiʻi’s coral reefs are an economic lifeline and intricately connected to people’s wellbeing.
Background Image: A monk seal swims over coral
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From global waters to local shores
Hawaiʻi critically needs to understand how ocean conditions are changing and vary by island and location. Global models don’t have the resolution we need.
Hawaiʻi is only one or two dots in the entire ocean with commonly used global models.
Until now, we weren’t able to capture the finer scale variability needed to better model what’s happening in a way that communities can plan for risk.
Comparison of sea surface temperature simulations for the Main Hawaiian Islands. The coarse-resolution Community Earth System Model (CESM) model (left) misses finer coastal detail, while the downscaled Regional Ocean Modeling System (ROMS) simulation (right) captures island landmasses and surrounding ocean features more accurately (Friedrich et al., 2024; Liu et al., 2023).
The team linked projections of what conditions will look like for Hawaiʻi with an economic valuation of changes in recreational reef use across the Hawaiian Islands. Results show that estimated reef loss is projected to cause substantial reductions in recreational value, up to $2.1-3.3 billion through 2100 across the Hawaiian Islands with some communities more at risk.
The fine-scale resolution revealed that even on the same island, projections from ocean acidification vary. For example, differences in coral reef resilience will impact the Kona and Hilo coasts of the Big Island differently. Kona’s reefs are more susceptible to ocean acidification and projected to degrade faster, potentially leading to longer-term economic challenges. In contrast, Hilo’s reefs are projected to fare better, which could boost tourism there. This information is valuable for local tourism, marine resource managers, and decision-makers in specific adaptation planning efforts like the Holomua Marine 30×30 Initiative and the Hawaiʻi OA Action Plan.
Background Image: Coral Reef in Kona and the Four Mile Beach in Hilo.
Bringing the modeling and economics together, the research team assessed vulnerability to identify which communities are most at risk. They calculated a vulnerability index using a suite of indicators representing dependence on marine resources. Socioeconomic information such as income, occupational diversity, and percent under the poverty line was also incorporated into the vulnerability index using data from the American Community Survey led by the US Census Bureau. This work integrated community exposure, their sensitivity and ability to adapt.
This map displays Vulnerability Index values, which combine exposure, sensitivity, and adaptive capacity to allow for comparison across different Shared Socioeconomic Pathways (SSP). The labeled communities are projected to have the highest vulnerability by the end of the century.
Enhancing local resilience to acidification
Some urban communities such as Honolulu and ‘Ewa – despite greater resources – had high sensitivity attributed to reliance on marine resources, commercial fishery engagement and ocean recreation. Strategies that reduce exposure can benefit these communities. While adaptive capacity was high throughout the Hawaiian Islands, rural communities—particularly on Hawaiʻi Island—generally demonstrated lower capacity. This finding underscores the necessity for targeted capacity-building support in these areas. The creation of this integrated assessment of vulnerability, which combines exposure, sensitivity, and adaptive capacity, reveals nuances not captured by any single measure.
These analyses can provide the foundation for more targeted and informed adaptation strategies that direct resources to areas where they can have the greatest impact.
Background Image: View of Honolulu, Hawai’i from Diamondhead
Building resilience requires an integrated approach that takes into consideration both the ecological and societal outcomes. For Hawaiʻi, coral reefs also face multiple stressors and ocean acidification is just one challenge they face. Next steps for the research team include identifying the potential for coral reefs to adapt to heat stress, identifying potential refugia from ocean conditions, and refining social vulnerability maps to fine-tune actions to enhance community resilience.
Background Image: Diamondhead at sunrise
Learn more about this project:
Background Image: A school of Hawaiian Dascyllus hover above a coral head off of Maui.
Funding Acknowledgement:
This work was supported by the US National Oceanic and Atmospheric Administration (NOAA) Grant NA21OAR0170191.
