Natural and anthropogenic changes to mangrove distributions in the Pioneer River Estuary (QLD, Australia)

We analyzed a time series of aerial photographs and Landsat satellite imagery of the Pioneer River Estuary (near Mackay, Queensland, Australia) to document both natural and anthropogenic changes in the area of mangroves available to filter river runoff between 1948 and 2002. Over 54 years, there was a net loss of 137 ha (22%) of tidal mangroves during four successive periods that were characterized by different driving mechanisms: (1) little net change (1948– 1962); (2) net gain from rapid mangrove expansion (1962–1972); (3) net loss from clearing and tidal isolation (1972–1991); and (4) net loss from a severe species-specific dieback affecting over 50% of remaining mangrove cover (1991–2002). Manual digitization of aerial photographs was accurate for mapping changes in the boundaries of mangrove distributions, but this technique underestimated the total loss due to dieback. Regions of mangrove dieback were identified and mapped more accurately and efficiently after applying the Normalized Difference Vegetation Index (NDVI) to Landsat Thematic Mapper satellite imagery, and then monitoring changes to the index over time. These remote sensing techniques to map and monitor mangrove changes are important for identifying habitat degradation, both spatially and temporally, in order to prioritize restoration for management of estuarine and adjacent marine ecosystems

Spatial Ecology of Mangrove Forests:A Remote Sensing Perspective

Over the past few decades, a diverse range of remote sensing data have been acquired over mangrove areas in different modes and with varying spatial resolutions and temporal frequencies, with these used to advance our understanding of mangrove ecosystems and their response to natural and human-induced change. Detailed information on the floristic composition, structure, biomass and growth stage of mangroves and changes in these attributes over time and at different scales of observation has been obtained and the knowledge gained has been to better inform on, for example, carbon dynamics, floral and faunal diversity, connectivity with adjacent environments, and responses to changing hydrological regimes and climate. Significant opportunities also exist for more effective use of these data for actively managing mangroves and the services they provide and ensuring that they are not overexploited and their integrity within the coastal environment is maintained. The benefits of including these data in mangrove characterization, mapping and monitoring programs are demonstrated using case studies from a wide range of locations, including in Australia, Southeast Asia and central America, and instruments such as radar, lidar and optical sensors. Local to global efforts aimed at monitoring mangrove dynamics using remote sensing data are also increasing, with these leading to more informed decisions in relation to conservation, management and sustainable use. The authors would like to acknowledge Jorg Hacker of Airborne Research Australia (ARA) for providing LIDAR data for the Gulf of Carpentaria and the Japanese Space Exploration Agency (JAXA) for access to Japanese L-band SAR data