Natural causes of wildfires, like lightning strikes, are rare on Pacific Islands, but these islands still boast a long history of fire.

Researchers supported by the Pacific Islands CASC explored the history of fire on nine islands that span almost 2,000 miles of the Pacific Ocean. Their study, published in the Journal of Biogeography, examined how vegetation type, soil type, and climate interact to affect wildfire regimes on the islands of Palau, Yap, Guam, Rota, Tinian, Saipan, Chuuk, Pohnpei, and Kosrae.

The researchers showed that increases in charcoal and pollen from native savanna plants coincide with human settlement on the islands 3-4,000 years ago. This correlation suggests the deliberate use of fire by humans to shape vegetation patterns on the landscape and is further supported by evidence that soil type alone does not explain vegetation patterns. As much as 10% of the land area would burn each year on certain islands, especially in locations where rainfall exhibits higher seasonality and at times when El Niño events intensify drought. Compared to Hawaiʻi, where invasive grasses dominate fire-prone landscapes, savannas on Micronesian islands where fires predominantly occur consist mostly of native plants. This research challenges perceptions of savannas as “degraded” landscapes and emphasizes the cultural significance of fire use in Micronesian land care systems.

This Pacific Islands CASC-supported research improves scientific understanding of the historic and current relationship between climate, fire, and land management. 

This research was supported by the Pacific Islands project “Climate Change, Variability, and Drought in the U.S.-Affiliated Pacific Islands – Working with Managers to Mitigate the Impacts of Drought and Wildfire.”