Risks to the future health and productivity of tropical estuaries under climate change and increasing human...

The wet-dry tropics of much of northern Australia, from Cape York to the Kimberley, contain some of the most pristine tropical estuaries globally. These estuaries have been under-researched, but provide a unique opportunity to understand the functioning of estuaries prior to intensive human impacts. The region is also under pressure from land-based development and climate change. Therefore we review, for the first time, the current knowledge of the ecology of these estuaries, then examine the potential effect of these stressors on the health and functioning of these estuaries. Flow alteration to provide water for irrigated agriculture is the development activity most likely to have a significant impact on estuaries in this region in the short- to medium-term. This flow alteration will reduce sediment and nutrient loads downstream, and reduce the scale of wet season flooding into saltmarshes and mangroves adjacent to estuaries. Faunal growth and reproduction in these systems is strongly cued to flow events and therefore are likely to be affected by flow alteration. Climate change impacts, such as extended droughts, will exacerbate the reduced flow from water development. Sea level rise and increased evapotranspiration are likely to have major impacts on the ecological functioning and habitat structure of estuaries. Our review demonstrates that our knowledge of the ecology of many of these estuaries remains limited, and therefore we identify key knowledge gaps related to the physical, chemical and biological attributes of estuaries which impede our ability to accurately predict future impacts of land-based development and climate change.