Wetlands Australia 31: Grey Mangroves at Sydney Olympic Park are affected by climate change and sea level rise

Authors: Dr Swapan Paul, Wetlands Manager, Sydney Olympic Park Authority and Adjunct Researcher, Charles Sturt University - Institute for Land, Water and Society

The wetlands at Sydney Olympic Park, located on a temperate estuary in south east Australia, have been subject to harmful impacts of climate change and sea level rise.

The impacts are seen in two major categories:

• habitats and ecosystems, and
• services and related assets in the Park.

Field observations and monitoring suggest that the grey mangrove Avicennia marina is impacted by climate change and associated sea level rise, which are affecting mangrove coverage and the normal cycle of flowering and fruiting. The effects are coming from various sources. Temperature shock is the most noticeable factor. Sudden drop in the night-time temperature or prolonged high day-night temperatures during February can kill early flowers, stopping flowers from setting early fruits. Such shifts in temperatures are becoming increasingly regular in this area.

Another aspect of the impact is seen in the form of persistently higher local sea levels, which in turn drown some satellite mangrove patches. Rising sea levels result in deeper water and longer periods of tidal residence in these mangroves. Although mangroves handle regular tidal inundations; water-logging is not tolerated. This situation is further exacerbated when excessive sediment washes down from upper catchments and clogs drainage channels. Ultimately, mangroves die within days from ponding. To rectify the drainage situation, tidal channels are being planned so that, even with rising sea levels, the areas drain quickly enough to avoid stress to mangroves.

Boardwalk tide damage. Photo: Sydney Olympic Park Authority

Climate change and its induced impacts are also putting Park management under financial pressure. In recent years, paths next to inter-tidal wetlands have been more frequently flooded by tides, resulting in a need to raise the paths. Similarly, a very long boardwalk inside a mangrove area was also affected and it was recently raised and replaced.

Early monitoring and understanding of the vulnerability of wetlands to likely and actual impacts of climate change and sea level rise can help save our wetlands and potentially avoid huge expenses in the near future.

Flooding. Photo: Sydney Olympic Park Authority

Further information

Email: Swapan.Paul@sopa.nsw.gov.au

WET e-book: Workbook for managing urban wetlands in Australia