Contributions to an Australian Mangrove Monitoring System
The need for a mangrove monitoring system for Australia was highlighted by the 2015/2016 dieback event across the northern coastline which has resulted in the mortality of over 7000 ha of mangroves (Duke et al., 2017) over a period of several months. Such an event was unexpected given that previous remote sensing observations had reported a steady landward and seaward expansion of mangroves along sections of this coastline since 1985 (Asbridge et al., 2016a,b). Ongoing monitoring is also vital as beyond the initial alert, there is not overall indication as to whether the mangroves are continuing to dieback or are recovering.
The following sections outline the basis behind an Australian Mangrove Monitoring System that can be supported by TERN Landscape Assessment and provide a range of openly available datasets to support scientific research and conservation, management and sustainable utilisation of mangroves and policy development and evaluation. The TERN Mangrove Data Portal provides key elements that can contribute to a mangrove monitoring system for Australia. A wide range of datasets are available through the portal and capacity has been provided to allow continual upload of new and existing datasets.
- The collation of freely available historical field data relating to mangroves.
- The development and formulation of near real time observations, with particular focus on the use of Open Data Kit (ODK) forms and mobile applications.
- A mangrove component of the Australian Plant Biomass Library (APBL), with a separate component considering allometric equations for mangrove species.
- The collation of freely available historical airborne data for Australia, with these including aerial imagery, hyperspectral and lidar data, drone imagery and derived products (e.g., canopy height models of CHMs).
- Targeted collection of airborne LIDAR data over extensive tracts of mangroves, thereby providing a baseline against which to establish changes in forest structure and biomass.
- Radar observations of mangroves, particularly at L-band, and linkages with the Japanese Space Exploration Agency’s (JAXA) Kyoto and Carbon (K&C) Initiative Global Mangrove Watch (GMW).
- Annual with capacity for sub-annual (at least fortnightly) analysis of mangroves using Landsat and Sentinel-2 sensor data processed routinely through Digital Earth Australia (DEA) platform.
- The use of Planet’s CubeSat and RapidEye data for near daily and potentially daily monitoring of mangroves and mangrove change at high (3-5 m) spatial resolution.
- The integration of climate and other environmental datasets with remote sensing observations to better understand the response of mangroves to human-induced and natural change, including that associated with human-driven climate change.
- The generation of automated historical and near real time alert detections.
- Assessments of the causes and consequences of changes in Australian mangroves.
National Mangrove Legend
For Australia, maps of mangrove species are provided for the north eastern Australian coastline (Hay et al., 2005), and also parts of the Northern Territory (Peter Brocklehurst, pers. comm). Through consultation with scientists in the states and territories, a nationally applicable legend was proposed (Figure). This considered a number of different EVs including dominant species (%), species mixtures, crown cover and height classes (to form a structural classification).
Asbridge, E., Lucas, R., Ticehurst, C. & Bunting, P. Mangrove response to environmental change in Australia’s Gulf of Carpentaria. Ecol. Evol. 6, 3523–3539, doi:10.1002/ece3.2140 (2016).
Duke, N. C. et al. Large-scale dieback of mangroves in Australia’s Gulf of Carpentaria: a severe ecosystem response, coincidental with an unusually extreme weather event. Mar. Freshwat. Res, doi:10.1071/MF16322 (2017).
Hay, T., Gribble, N., De Vries, C., Danaher, K., Dunning, M., Hearnden, M., Caley, P., Wright, C., Brown, I., Bailey, S., Phelan, M., 2005. Methods for monitoring the abundance and habitat of the northern Australian mud crab Scylla serrata. Final Report, FRDC Project 2000/142, Northern Territory Government, Darwin. Retrieved from: https://www.frdc.com.au/Archived-Reports/FRDC%20Projects/2000-142-DLD.PDF