Agroforestry key to Hawai‘i’s carbon-neutral goals, new UH study reveals

A new study out of the University of Hawai‘i reveals that converting unused agricultural lands to agroforestry systems could help reduce extreme fire risks, boost food production and revive Indigenous and place-based land management practices.

This conversion would also help the state meet its 2045 carbon neutrality target, according to a press release from the university.

The study, done by an interdisciplinary team at the University of Hawaiʻi at Mānoa, Kamehameha Schools and the Institute of Pacific Islands Forestry, found that more than 370,000 acres of Hawaiʻi’s unmanaged agricultural land — an area roughly the size of Oʻahu — is suitable for agroforestry under current climate conditions.

Even under projected drier conditions by mid-century, almost 300,000 acres, larger than the size of Los Angeles, would remain viable, the release stated.

The study, published in Scientific Reports, evaluates the suitability of currently unmanaged agricultural land for transitions to agroforestry systems that combine native and other valued trees with crops and other tended products. According to the press release, the authors then modeled carbon storage in these systems based on the types of canopy and midstory trees present in current agroforestry systems in Hawaiʻi.

Researchers estimate that restored systems could store 92–125 metric tons of carbon per hectare just in the above-ground vegetation, which is similar to native forests.

“Our study demonstrates the importance of Indigenous and place-based agroforestry as a multi-benefit system that can sequester carbon while also producing local food and providing a suite of other cultural, ecological and economic benefits,” said lead author Leah Bremer, associate director at the Institute for Sustainability and Resilience, and faculty associate specialist at UHERO and Water Resources Research Center.

Results of the study suggest that three-quarters of the potential restoration area would significantly increase carbon storage compared to the current land cover (mostly non-native grasslands and shrublands).

Researchers also found that benefits would be highest in areas that were previously in pineapple and sugar plantations as there is the greatest potential to increase soil carbon storage through agroforestry transitions in areas where soils have been degraded through intensive cultivation.

They find that transitioning all potential areas would reduce emissions by about 42 million metric tons of carbon dioxide over 30 years, equivalent or roughly the equivalent of 100 million barrels of oil, which is about two years of oil use across the state of Hawaiʻi.

The study suggests that agroforestry offers an effective natural climate solution for agricultural zoned lands that also supports local communities and food security.

The research team combined interviews with agroforestry practitioners, literature review and spatial modeling to evaluate potential carbon benefits across different rainfall zones and soil types throughout the Hawaiian Islands.