An Evaluation of Vegetation Loss Due to Super Typhoon Sarika in Hainan Island of China

Abstract With the aggravation of global climate change, various extreme climate events have become increasingly prominent. Super typhoon is the most disastrous event that causes severe loss to the economy, agriculture, transportation, communication, and ecosystem in coastal regions. Super typhoon severely impacts ecosystem structure and function and even leads to ecosystem degradation. In the current study, we assessed the impact of a super typhoon Sarika on vegetation in the tropical landscape of Hainan Island. The super typhoon Sarika that hit Hainan Island on 18 October 2016 lasted for 15 h and was the most severe typhoon affecting Hainan Island in October since 1970. The coastal land around Hainan Island generally faced gales with a wind speed of 35 m/s (maximum wind speed of 46.1 m/s), causing severe agriculture, forestry, and the social economy. In the present study, we evaluated the impact of the super typhoon Sarika on vegetation by performing NDVI (Normalized Difference Vegetative Index) difference analysis using MODIS multi- temporal images acquired before and after the typhoon. The assessment of typhoons depends on the land use types, landscape topography of slope, aspect, and altitude. The results indicated that the super typhoon Sarika seriously hit forestry, agriculture, shrubs, plantations, and orchards in Hainan Island. Overall, 79% of vegetation exhibited a negative change, whereas only 21% of vegetation exhibited a positive change in NDVI after the super typhoon Sarika. Agriculture (including dry land and paddy field agriculture) was most severely damaged by the typhoon, where more than 81% of areas exhibited a decrease in NDVI, followed by plantations and orchards, where 77% of areas exhibited a decrease in NDVI. Additionally, the damage to vegetation due to typhoons was affected by abiotic factors such as altitude, slope, and aspect. Our study reported that damage due to the super typhoon was associated with land cover types, altitude, aspect, and slope. In low altitude plain and coastal areas, NDVI decreased more in this super typhoon Sarika, consistent with the distribution of typhoon gale. Additionally, the current study demonstrated that MODIS images with a spatial resolution of 250 m could rapidly evaluate quantitative and accurate vegetation damage from the macro scale.