Quantifying mangrove canopy regrowth and recovery after Hurricane Irma with large-scale repeat airborne lidar in the Florida Everglades

• Published in: International journal of applied earth observation and geoinformation 2022-11, Vol.114, p.103031, Article 103031
• Main Authors: Xiong, Lin, Lagomasino, David, Charles, Sean P., Castañeda-Moya, Edward, Cook, Bruce D., Redwine, Jed, Fatoyinbo, Lola
• Format: Article
• Language: English
• Subjects: Canopy height model; Earth Resources and Remote Sensing; Everglades; Hurricanes; Lidar; Mangrove forests; Recovery; South Florida
• ISSN: 1569-8432; 1872-826X
• DOI: 10.1016/j.jag.2022.103031

•Impact of Hurricane Irma on mangrove canopy height was assessed with large scale repeat airborne lidar.•Airborne lidar was collected before, 3-months, 2.5 years after the storm, representing of the largest repeat lidar surveys in mangrove forests to date.•Only 38.1 % of mangroves had recovered to pre-storm canopy height 2.5 years post-hurricane.•Canopy structure showed little or no recovery in highly damaged regions post-Irma.•Recovery varied by resilience classes, species composition, and canopy height. Hurricane Irma caused significant damages to mangrove forested wetlands in south Florida, including defoliation, tree snapping, and uprooting. Previous studies have used optical satellite imagery to estimate large-scale forest disturbance and resilience patterns. However, satellite images alone cannot provide measurements of vertical mangrove structure. In this study, we used dense point cloud data collected by NASA Goddard’s LiDAR, Hyperspectral, and Thermal (G-LiHT) airborne imager before (March 2017) and after (December 2017 and March 2020) Hurricane Irma to quantify the recovery, or lack thereof, of the three-dimensional (3D) mangrove forest structure. Recent resilience and vulnerability models developed from Landsat time series following the storm were used to group the lidar data into distinct disturbance-recovery classes. We then analyzed lidar-based forest canopy within each of the recovery classes to test a suite of forest structural characteristics. Our results indicate that 77.0 % of the survey area experienced canopy height loss three months after Hurricane Irma, whereby the majority of canopy height loss occurred in areas with the tallest mangrove forests (i.e., 15–25 m tall). Our analysis shows that the mangrove canopy height in South Florida increased by an average 0.26 m from December 2017 to March 2020, with most of the forest (84.7 % of the survey area) experiencing canopy height regrowth. However, only 38.1 % of the survey area has recovered to pre-storm canopy height. The distribution of canopy height was significantly altered by Hurricane Irma in the low and intermediate resilience classes, but were not significantly different 2.5 years later. Indeed, in areas of low resilience, little to no vertical change has occurred suggesting the absence of canopy regrowth and natural regeneration. Conversely, mangroves in high resilience class, which are dominated by shorter canopies (