| 要旨トップ | 目次 | | 日本生態学会第72回全国大会 (2025年3月、札幌) 講演要旨 ESJ72 Abstract |
一般講演(口頭発表) C03-01 (Oral presentation)
Intense and frequent tropical cyclones (TCs) pose a major disturbance to mangroves amid global climate change. Evaluating the spatiotemporal dynamics and recovery of mangroves following TC disturbances is crucial for mangrove conservation and restoration. However, the long-term effects of TCs on the spatial extent of large-scale mangrove forests remain unclear. The Sundarbans, Bangladesh, the largest continuous mangrove forest, is exposed to strong winds and is increasingly vulnerable to TC disturbances. To clarify the effects of TCs on mangroves, forest disturbance patterns related to TCs and environmental factors from 1988 to 2024 were quantified by remote sensing. Mangroves were mapped through the enhanced vegetation index (EVI) from Landsat TM (30 m resolution) reflectance data via Google Earth Engine. Spatiotemporal changes in EVI over 36 years were evaluated using the Mann-Kendall test and Theil-Sen median trend analysis. Forest disturbances were assessed by comparing pre-and post-EVI of 32 TCs. The forest areas were analyzed in relation to TCs (wind speed and track distance), temperature, precipitation and elevation by structural equation modeling (SEM). Interannual mangrove changes showed an increasing trend from 1988-1999 and 2011-2024, whereas a decrease occurred from 2000 to 2010, indicating the effects of TC disturbances. EVI-based forest disturbance mapping estimated a decline of 0.2% to 22% of the total 5,980 km2 forest area following TCs. Among the 32 TCs, the most severe forest disturbance (22%) was caused by a category 5 (on saffir-simpson hurricane wind scale) TC in 2007. SEM revealed wind speed as the highest predictor of forest disturbances, with direct positive effects on forest areas. TC track distance from the centroid and precipitation were related to forest disturbances, highlighting the sensitivity of mangrove vegetation to strong TCs making landfall with increasing precipitation. Trunk and stem breakage, along with uprooted trees caused by high wind speeds and increased exposure, likely decrease EVI afterward a TC strikes. While mangrove forests showed revegetation within a few years after a TC, intense and frequent TCs should hinder regeneration, threatening mangrove forests and their critical role in coastal bio-protection. These findings underscore the expected effects of TCs on mangroves, thereby encouraging sustainable conservation and restoration strategies to prioritize mangrove forest resilience.