Sediment processes and mangrove-habitat expansion on a rapidly-prograding muddy coast, New Zealand Other Publication
- Author
- A Swales, SJ Bentley, C Lovelock, RG Bell
- Year
- 2007
- Journal / Source
- Coastal Sediments ‘07
- Publisher / Organisation
- Proceedings of the Sixth International Conference on Coastal Engineering and Science of Coastal Sedimentation Processes, New Orleans, May 2007
- Pages
- 1441-1454
- Species
- Avicennia marina subsp. australasica, manawa, mangrove, Avicennia marina, Avicennia marina var. resinifera, Avicennia resinifera
- Keywords
- Firth of Thames, deforestation, sedimentation, mangrove
- Summary
- Mangrove-habitat expansion has occurred rapidly over the last 50 years in the 800 km2 Firth-of-Thames estuary (New Zealand). Mangrove forest now extends 1-km seaward of the 1952 shoreline. The geomorphic development of this muddy coast was reconstructed using dated cores (210Pb, 137Cs, 7Be), historical-aerial photographs and field observations to explore the interaction between sediment processes and mangrove ecology. Catchment deforestation (1850s–1920s) delivered millions of m3 of mud to the Firth, with the intertidal flats accreting at 20 mm yr–1 before mangrove colonization began (mid-1950s) and sedimentation rates increased to ⩽ 100 mm yr–1. 210Pb data show that the mangrove forest is a major long-term sink for mud. Seedling recruitment on the mudflat is controlled by wave-driven erosion. Mangrove-habitat expansion has occurred episodically and likely coincides with calm weather. The fate of this mangrove ecosystem will depend on vertical accretion at a rate equal to or exceeding sea level rise.