Impact Assessments of Typhoon Lekima on Forest Damages in Subtropical China Using Machine Learning Methods and Landsat 8 OLI Imagery

Abstract

Wind damage is one of the major factors affecting forest ecosystem sustainability, especially in the coastal region. Typhoon Lekima is among the top five most devastating typhoons in China and caused economic losses totaling over USD 8 billion in Zhejiang Province alone during 9–12 August 2019. However, there still is no assessment of its impacts on forests. Here we detected forest damage and its spatial distribution caused by Typhoon Lekima by classifying Landsat 8 OLI images using the random forest (RF) machine learning algorithm and the univariate image differencing (UID) method on the Google Earth Engine (GEE) platform. The accuracy assessment indicated a high overall accuracy (>87%) and kappa coefficient (>0.75) for forest-damage detection, as evaluated against field-investigated plot data, with better performance using the RF method. The total affected forest area by Lekima was 4598.87 km2, accounting for 8.44% of the total forest area in Zhejiang Province. The light-, moderate- and severe-damage forest areas were 2106.29 km2, 2024.26 km2 and 469.76 km2, respectively. Considering the damage severity, the net forest canopy loss fraction was 2.57%. The affected forest area and damage severity exhibited large spatial variations, which were affected by elevation, slope, precipitation and forest type. Our study indicated a larger uncertainty for affected forest area and a smaller uncertainty for the proportion of damage severity, based on multiple assessment approaches. This is among the first studies on forest damage due to typhoons at a regional scale in China, and the methods can be extended to examine the impacts of other super-strong typhoons on forests. Our study results on damage severity, spatial distribution and controlling factors could help local governments, the forest sector and forest landowners make decision on tree-planting planning and sustainable management after typhoon strikes and could also raise public and governmental awareness of typhoons’ damage on China’s inland forests.

Tropical cyclone winds and precipitation stimulate cone production in the masting species longleaf pine (Pinus palustris)

“…Tropical cyclones (TCs) are common in the Atlantic and Pacific Oceans (Patricola et al ., 2022), and masting is common among several tree species that occur in forests prone to TCs, including ecologically dominant genera such as Quercus , Pinus , Picea , and Nothofagus (Table 1). Mortality from TCs affects forest dynamics in a broad range of forests across the globe (Boose et al ., 2001; Van Bloem et al ., 2006; Lee et al ., 2008; Altman et al ., 2013; Chen et al ., 2014; Dahal et al ., 2014; Zampieri et al ., 2020; Rutledge et al ., 2021; Zhang et al ., 2021). Because of the high global incidence of TC activity and masting, it is important to understand whether, and how, cyclones may relate to reproductive behavior in masting species.…”

Physical vulnerability curve construction and quantitative risk assessment of a typhoon-triggered debris flow via numerical simulation: A case study of Zhejiang Province, SE China

“…Debris flows pose a frequent and devastating geological hazard in mountainous areas causing a significant threat to human life, property, and infrastructure (Tang et al, 2009;Ouyang et al, 2019). The south-eastern coast of China is particularly affected by debris flows due to heavy rainfall caused by typhoons (Zhao et al, 2018;Zhang et al, 2021). On August 10th, 2019, Super typhoon Lekima produced extremely concentrated rainfall in the northern part of Zhejiang province, triggering numerous debris flows causing significant loss of life and property damage (Nie et al 2021;Zhou et al 2022;Liang et al 2022).…”

Hurricane wind regimes for forests of North America

“…Tropical cyclones occur among seven basins in the Northern and Southern portions of the Atlantic and Pacific Oceans. The Northwestern Pacific Ocean is the most active basin accounting for 40% of global tropical cyclone activity ( 3 ) and commonly leads to forest disturbance in China, Taiwan, and the Korean peninsula ( 4 – 6 ). The North Atlantic Ocean Basin accounts for only 15% of global tropical cyclone activity, yet the region has produced cyclones with immense impacts on forests of the United States, Caribbean, and Central America ( 7 – 10 ).…”