Hurricane-Induced Changes in the Everglades National Park Mangrove Forest: Landsat Observations Between 1985 and 2017

The Everglades National Park (ENP) has one of the largest mangrove forests in the United States, yet due to lack of data and methods, there has been no multidecadal record of detailed changes in its mangrove forests, not to mention their response to periodic hurricanes. Here, based on remote sensing spectroscopy, multisensor cross calibration, spectral normalization, and pixel unmixing, we develop a stepwise method to map distributions and changes of the ENP mangrove forests and other major wetlands cover types (marshes and hardwood hammocks) over the last three decades. The time series of Landsat-based results indicate statistically significant increasing trend from 1985 to 2017 in the total ENP mangrove coverage with a cumulative increase of 10.2%, which has increased in the inner coastline area but decreased in the outer coastline area. The mangrove coverage also decreased considerably in certain hurricane years (1992, 2005, and 2017), with the largest decrease of 644.9km(2) (46.5% of the mean mangrove area in normal years) occurring in 1993 after Hurricane Andrew. Yet, these large mangrove die-off areas gradually recovered to prehurricane levels 3-4years after the passage of major hurricanes. Results also indicate that while the mangrove forests were always damaged by hurricanes, the extent of the damage depended on wind speed, direction, and distance from maximum wind. The findings here could serve as baseline information for future restoration efforts of the ENP ecosystem, and the study also provides a method extendable to other coastal wetland regions.