A lot has changed since the 1980s—think the internet, phones, smoking etc—but what about Australia’s mangrove ecosystems and their ability to support faunal biodiversity, filter pollutants, protect marine ecosystems, reduce coastal erosion and storm damage, and store carbon?
Thanks to a new collaborative study utilising decades of satellite data, the maps and data are now openly available to assist in answering these important questions.
Dr Leo Lymburner of Geoscience Australia leads the team that has used satellite data from Digital Earth Australia (DEA) and maps from Global Mangrove Watch (GMW) to show the dynamics of Australia’s mangroves for a 30-year period leading up to the 2016 dieback event.
These maps are the first to be generated at a continental scale on an annual basis, and are now openly available via TERN’s Mangrove Data Portal.
The expansion of mangroves between 1994 and 2010 (top) and decreases in mangrove extent between 2010 and 2016 (bottom) (image courtesy of Lymburner et al 2019)
Mangrove ecosystems in Australia are protected by state, national and international legislation but are still highly vulnerable to adverse environmental change, says Leo’s fellow mangrove researcher Professor Richard Lucas of Aberystwyth University in Wales. Richard says that this research adds to the general understanding that dieback and regrowth of mangroves is likely to be cyclical and dependent on a number of climatic and oceanic factors.
Richard says that mangrove ecosystems can also migrate geographically over time, with this largely occurring because of physical changes in the coastline. However, areas of mangroves which have remained in the same position over time have a higher conservation importance due to their role as long-term refugia during unfavourable climatic fluctuations.
More research using these maps is required, but it may be the case that mangroves will return to their 80s extent—perhaps in the same way that 1980s fashion statements such as the ruffles, metallic colors, shoulder pads and mullets have resurfaced in 2019!
Junction Bay, Northern Territory, where mangroves experienced losses in extent and cover in 2003 and 2006 as a result of category 3 (severe tropical cyclone Debbie) and 5 (severe tropical cyclone Monica) tropical storms respectively. Note that the 2003 image is prior to the impact of Debbie. The column chart indicates the extent and cover during the pre- and post-cyclone periods. (image courtesy of Lymburner et al 2019)
Work is ongoing for Leo and his colleagues, whose future efforts are focusing on the routine production of annual mangrove maps beyond 2019.
As new maps are created they will be made available through the Australia Government’s National Map and the TERN Mangrove Data Portal, which already provides open access to decades of historical and newly acquired field and Earth observation data.
The Australia State of the Environment 2016 report highlighted that there is a lack of coordinated national mangrove monitoring and evaluation of ecosystem function, productivity and condition. According to Professor Graciela Metternicht of the University of New South Wales, the nationally consistent mapping protocol that this project has established goes a long way towards filling this gap.
In addition to being openly available via TERN, the new maps of mangrove extent are also viewable in the Australian Government’s National Map
Published in TERN newsletter August 2019