Spatial and Temporal Patterns of Fire on Saipan, CNMI

Abstract: Sediment core studies from Saipan suggest that fires did not play a prominent role in the disturbance regime of the Mariana Islands and have increased in frequency since human settlement around 4,000 years ago. On Saipan fires are understood to interrupt the pattern of succession leading to the degradation of native limestone forests, the proliferation of grasslands and the eventual creation of badlands. Little baseline data regarding the spatial and temporal patterns of fire on Saipan exist to create effective Fire Management Plans. This project uses Landsat 8 images from April 2013 to July 2020 and the Normalized Burn Ratio to identify historic fires to evaluate patterns that will inform on effective fire management policies. Over the study period we detected 1,608 ha of burnt land, in four specific hotspots. Of the area burned, 40% were in grasslands, 31% in evergreen forests, and 21% in scrub-shrub. 41% of all hectares that burned more than once throughout the study period were grasslands, indicating that this was the landcover type most vulnerable to repeat burn events. We also found a strong seasonal trend, with the average amount of burnt land detected in the dry season 280% higher than the average amount of burnt land detected in the wet season. Finally, both total precipitation and the absence of precipitation were highly correlated to the amount of burn area identified (P < .05). The information elucidated through this study will be used by local agencies to implement management plans geared toward controlling wildfires.