WETLANDS AND CLIMATE CHANGE Climate Change Impacts on the Coastal Wetlands of Australia N. Saintilan 1 & K. Rogers 2 & J. J. Kelleway 1 & E. Ens 1 & D. R. Sloane 1 Received: 30 May 2017 /Accepted: 6 February 2018 # Society of Wetland Scientists 2018 Abstract The Australian continent spans coastal wetland settings ranging from extensive mangrove forest and sabkha plains occupying in the tropical north, to the southern half of the continent, where high wave energy constrains wetlands within numerous barrier- fronted estuaries, drowned river valleys and coastal embayments. Only on the island of Tasmania are mangroves absent; elsewhere mangroves, Casuarina, Melaleuca and saltmarsh interact in ways illustrative of the effects of ongoing climate, tidal and sea-level change. Observations over several decades have suggested that recent anthropogenic climate change may already be impacting Australian coastal wetlands in important ways. A period of accelerating sea-level rise has been associated with saline intrusion, mangrove encroachment and Melaleuca dieback in the tropical north, punctuated by widespread mangrove mortality in drought periods. The consistent trend of mangrove encroachment and replacement of saltmarsh in the south, is associated with an Baccretion deficit^ in saltmarsh during contemporary sea-level rise. We review the ecological and cultural implications of these changes, including impacts on habitat provision for migratory birds, fisheries values, carbon sequestration and Indigenous cultural values. Current legislative and policy protections may not be sufficient to meet the increasingly dynamic impacts of climate change in altering wetland boundaries, composition and function. Keywords Mangrove . Saltmarsh . Melaleuca . Dieback . Salinisation . Australia Extent and Composition of Australian Intertidal Wetlands At the taxonomic levels of family and genus, Australian man- groves, saltmarshes, Casuarina spp. and the Bpaperbark^ Melaleuca spp. have strong affinities with species on other continents. Australian mangroves belong to the broader bio- geographic association of Old World mangroves, finding greatest diversity immediately to the north of the continent in Indonesia. Few species are endemic to Australia and there is a notable decrease in mangrove floristic diversity away from the tropics on both eastern and western Australian coastlines. Aridity is an important constraint on mangrove diversity and extent on the west coast (Duke et al. 1998). By contrast, saltmarsh floristic affinities are primarily Gondwanan, with strong similarities at family level with the saltmarsh flora of New Zealand, South Africa and temperate South America (Adam 1990; Boon et al. 2011). Saltmarsh diversity decreases towards the tropics, and the northern and southern halves of the continent, separated by 23 degrees latitude, form distinc- tive biogeographic provinces (Saintilan 2009). Often a feature of the landward intertidal zone, some coastal Melaleuca and Casuarina species are found across Australia and Malesia (e. g. Melaleuca cajuputi and Casuarina equisetifolia ) (ABARES 2013) as well as some in New Caledonia, Papua New Guinea and Lord Howe Island (Boland et al. 2006; Brophy et al. 2013). Intertidal areas are far larger in the tropical north due to high tidal ranges and the presence of large rivers depositing deltas and building floodplains into shallow continental shelves. Melaleuca or Casuarina-marsh-mangrove dynamics characterise the intertidal-supratidal zone which also com- monly encounters hypersaline conditions during the dry sea- son. Grassy flats, sedges and cyanobacterial Bsabkha^ flats are more commonly encountered than saltmarshes (Cowie et al. 2000). In the southern biogeographic provinces, coastlines are subject to high wave energy with intertidal environments * N. Saintilan neil.saintilan@mq.edu.au 1 Department of Environmental Sciences, Macquarie University, Sydney, Australia 2 School of Earth and Environmental Sciences, University of Wollongong, Wollongong, Australia Wetlands https://doi.org/10.1007/s13157-018-1016-7