Sydney Harbour emissions equivalent to 200 cars on the road
The first footprint of Sydney Harbour's carbon聽emissions has found it is roughly equivalent to similar estuaries in the US but significantly less than polluted water sources straddling build-up areas in Europe and Asia.
The CO2 emitted from Sydney Harbour is significant 鈥� but it鈥檚 a small amount for an estuary of that size.
Lead author, PhD candidate Edwina Tanner
The Sydney Harbour is renowned as a beautiful landmark straddling our thriving city聽 but a new study has shown it is also a source of significant carbon emissions, which requires careful management as the city is poised to double its population by the end of the century.
That is the message of new research that has quantified CO2 emissions from the Harbour for the first time 鈥� found to be 1000 tonnes annually 鈥� equivalent to the pollution from about 200 cars.
The research, by the University of Sydney鈥檚 and the at Southern Cross University, is the first long term study of such a large and important Southern Hemisphere system referred to as a drowned river valley, which in Sydney spans estuaries from Middle Harbour to Lane Cove and Parramatta.
The emissions from Sydney Harbour 鈥� including from urban runoff, leaf litter, soil decomposition and sewage overflow 鈥� were found to be very low compared to the highly polluted estuaries of Europe and Asia, which can emit up to 76,500 car CO2 equivalents each year.
Sydney鈥檚 emissions were found to be significantly less than China鈥檚 major dammed river, the Yangtze, which is adjacent to megacities including Shanghai. Sydney鈥檚 emissions measured at a similar, albeit lower level, to other natural drowned river valleys in the United States such as the Hudson River, which flows through New York.
Sydney is also predicted to become a megacity 鈥� with a population of 10 million 鈥� by 2100.
The research is published in the 5 June edition of the international journal .
Lead author and PhD candidate Edwina Tanner in the University of Sydney鈥檚 School of Geosciences, said although the Sydney Harbour was a net carbon emitter, during periods of high rainfall it became a carbon sink, as coastal waters filtered runoff from the highly urbanised catchment.
鈥淭he 1000 tonnes of CO2 we found are emitted from Sydney Harbour each year is significant 鈥� but it鈥檚 a small amount for an estuary of that size,鈥� said Ms Tanner, who will receive her PhD this year and is the Sydney Institute of Marine Science project manager of the .
The distinctive funnel shape of the Sydney Harbour Estuary drowned river valley system includes narrow upper estuary channels, where particulate matter is filtered, which link up to a wide lower estuary that is flushed with coastal waters.
Ms Tanner said monitoring of estuarine CO2 was important for planning and remediation efforts: 鈥淎s each estuary is different, the potential impacts of climate change and urban development will be different in every ecosystem.鈥�
Co-author and supervisor Professor Bradley Eyre from Southern Cross University, who has been studying estuaries for more than 20 years, said the research should play an important role in quantifying the significant carbon footprint of estuaries in built-up areas worldwide.
鈥淐omparing results with other global estuaries, the discharge per unit area of the Sydney Harbour provides a predictor of emissions for estuaries from a similar geomorphic class,鈥� he said.
鈥淎 detailed analysis of emissions from urban harbours around the world could provide an understanding of adaptation strategies needed to manage and protect estuaries globally from future development and climate change.鈥�
The research was supported by a postgraduate award to Ms Tanner, with additional funding provided by the Australian Research Council to Professor Eyre.