Characterising the Aboveground Carbon Content of Saltmarsh in Jervis Bay, NSW, Using ArborCam and PlanetScope  
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1 Faculty of Science, School of Geosciences, University of Sydney, Sydney, NSW 2006, Australia; [EMAIL_ADDRESS] (E.W.-C.); [EMAIL_ADDRESS] (E.B.) [PERSON]  
1 Faculty of Science, School of Geosciences, University of Sydney, Sydney, NSW 2006, Australia; [EMAIL_ADDRESS] (E.W.-C.); [EMAIL_ADDRESS] (E.B.) [PERSON]  
2 Centre for CubeSats, UAV and Their Applications (CUAVA), University of Sydney, Sydney, NSW 2006, Australia; p.barber@n hydrocarbon.com.au (Chanel Coastal Observatory, National Oceanographic Centre, Southampton SO14 3 ZH, UK) 24 ArborCarbon, Rota Trans 1, Murdoch, WA 6150, Australia; [EMAIL_ADDRESS] (c)  
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4 ArborCarbon, Rota Trans 1, Murdoch, WA 6150, Australia; [EMAIL_ADDRESS] (c)  
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1 Faculty of Science, School of Geosciences, University of Sydney, Sydney, NSW 2006, Australia; [EMAIL_ADDRESS] (E.W.-C.); [EMAIL_ADDRESS] (E.B.) coastal and marine 'blue carbon' stores that provide a key climate regulating service. Large declines in the global extent of coastal ecosystems have occurred, principally due to land conversion for coastal development [5; 6; 7] and, in some cases, due to changes in climate factors (e.g., air temperature and precipitation) [8]. The impacts of future climate change on the extent and functioning of coastal ecosystems is an active area of investigation. For example, there is evidence that sea-level rise may drive increases in coastal carbon storage, possibly mitigating potential climate feedback effects [9; 10], and increasing annual maximum temperatures may drive a landward shift and encroachment of mangroves into saltmarsh communities in Australia [11]. The accurate mapping and monitoring of coastal ecosystems, such as coastal saltmarsh, and their associated aboveground carbon content will aid in their protection and rehabilitation, which can be supported through adaptive coastal governance policies [2] and carbon accounting mechanisms such as REDD+ [12; 13]. Australian coastal saltmarsh ecosystems are intertidal plant communities that occupy the high tidal zone, often behind mangroves in areas sheltered from wave energy, such as estuaries [14]. These saltmarsh ecosystems are often characterized by short, patchy vegetation that often displays species zonation along salinity, elevation and inundation frequency gradients and presents in predominantly monospecific patches [15]. The total saltmarsh area in Australia is estimated to be 13,825 km\({}^{2}\)[16], and it is listed as vulnerable under the national Environment Protection and Biodiversity Conservation Act 1999. In the Australian state of New South Wales (NSW), the total saltmarsh area is estimated at 72 km\({}^{2}\)[17], and saltmarsh communities are listed as an Endangered Ecological Community under the state Threatened Species Conservation Act 1995. Both federal and state legislatures reinforce the need for the comprehensive monitoring and management of these important saltmarsh communities. Remote sensing has been used for decades as an effective tool for the environmental monitoring of large, vegetated areas due to reduced costs and the reduced need for extensive field-based sampling [18; 19; 20]. The applications of remote sensing to map and monitor saltmarsh vegetation have included the use of Landsat satellites to examine temporal trends [20; 21; 22] and the use of high spatial resolution airborne sensors and uncrewed aerial vehicles (UAVs) for mapping the saltmarsh vegetation structure [23; 24; 25]. In particular, multispectral remote sensing technology enables the quantification of aboveground biomass through the use of calibrated vegetation indices, such as the widely used Normalized Difference Vegetation Index (NDVI) [26; 27].