Abstract
Cyclones are significant drivers of change within mangrove ecosystems with the extent of initial damage determined by storm severity, location and distribution (exposure), and influenced by species composition and structure (e.g., height). The long‐term recovery of mangroves is often dependent upon hydrological regimes, as well as the frequency of storm events. On February 3, 2011, Tropical Cyclone Yasi (Category 5) made landfall on the coast of north Queensland Australia with its path crossing the extensive mangroves within and surrounding Hinchinbrook Island National Park. Based on a combination of Landsat‐derived foliage projective cover (FPC), Queensland Globe aerial imagery, and RapidEye imagery, 16% of the 13,795 ha of mangroves experienced severe windthrow during the storm. The greatest damage from the cyclone was inflicted on mangrove forests dominated primarily by Rhizophora stylosa, whose large prop roots were unable to support them as wind speeds exceeded 280 km/hr. Classification of 2016 RapidEye data indicated that many areas of damage had experienced no or very limited recovery in the period following the cyclone, with this confirmed by a rapid decline in Landsat‐derived FPC (from levels > 90% from 1986 to just prior to the cyclone to < 20% postcyclone) and no noticeable increase in subsequent years. Advanced Land Observing Satellite (ALOS‐1) Phased Arrayed L‐band Synthetic Aperture Radar (SAR) L‐band HH backscatter also increased initially and rapidly to 5 ± 2 dB (2007–2011) due to the increase in woody debris but then decreased subsequently to −20 ± 2 dB (postcyclone), as this decomposed or was removed. The lack of recovery in affected areas was attributed to the inability of mangrove species, particularly R. stylosa, to resprout from remaining plant material and persistent inundation due to a decrease in sediment elevation thereby preventing propagule establishment. This study indicates that increases in storm intensity predicted with changes in global climate may lead to a reduction in the area, diversity, and abundance of mangroves surrounding Hinchinbrook Island.
Highlights
Mangrove forests are distributed in the intertidal zone along subtropical and tropical coastlines, between approximately 30°N and 30°S latitude (Giri et al, 2011)
The greatest damage from the cyclone was inflicted on mangrove forests dominated primarily by Rhizophora stylosa, whose large prop roots were unable to support them as wind speeds exceeded 280 km/hr
This study indicates that increases in storm intensity predicted with changes in global climate may lead to a reduction in the area, diversity, and abundance of mangroves surrounding Hinchinbrook Island
Summary
Mangrove forests are distributed in the intertidal zone (usually from mean sea level to highest spring tide; Alongi, 2009) along subtropical and tropical coastlines, between approximately 30°N and 30°S latitude (Giri et al, 2011). Within Australia, there has been increasing concern regarding the impacts of climate change on the long-term health of mangroves and the impacts on biodiversity as well as society and economics This issue has gained greater prominence following the recent dieback event (Duke et al, 2017), which affected over 10,000 ha of mangroves in northern Australia. The concern is that changes in cyclone regimes in northern Australia might have a long-term impact on the viability of mangrove communities and compromise their ability to support ecosystem services For this reason, this study aimed to: 1. The reasons for change in mangrove structure and health and the patterns of destruction and recovery are discussed with reference to global and future implications
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