Document Type

Thesis

Publication details

Akumu, CE 2011, 'Assessing the potential impacts of climate change on coastal wetlands in North-Eastern NSW using geoinformatics', PhD thesis, Southern Cross University, Lismore, NSW.

Copyright CE Akumu 2011

Abstract

The coastal wetland communities of north-eastern New South Wales (NSW) Australia exist in a subtropical climate with high biodiversity and are already under threat due to several anthropogenic factors such as urbanisation, residential development and agricultural development. In addition, they are also potentially threatened by thecontinuous variation in climate. Nevertheless, there is no known research about the extent of the potential impacts of climate change on these delicate yet dynamic ecosystems. The aim of the study is to assess the potential impacts of climate change on the coastal wetlands in north-eastern NSW, Australia. In assessing the potential impact of climate change, it is important to examine a range of issues including the present extent and types of wetlands in the study area, the environmental requirements and tolerances of keystone wetland flora, inundation by elevated sea level and changes in biogeochemical processes that may result from elevated temperatures. The objectives are: (i) to provide an overview of wetland classifications in relation to their communities and their environmental variables with an emphasis on NSW; (ii) to map the current and past wetland communities in north-eastern NSW in order to identify any changes in quality and extent; (iii) to predict the potential spatial distribution of selected wetland species (Avicennia marina, Banksia integrifolia, Melaleuca quinquenervia and Leptospermumliversidgei) as a result of climate change (mean annual temperature increase); (iv) to predict the potential impact of sea level rise on the coastal wetland communities by the end of the century; (v) to estimate the amount of methane emission from the coastal wetlands using satellite data and to estimate emission with a temperature increase and (vi) to provide management, mitigation and adaptation strategies that could be used to minimize the impacts of climate change on the coastal wetland ecosystems.

Landsat TM satellite imagery of September 1989, February 2009 and Landsat ETM+ of June 2001 were used to identify, map and monitor the wetland communities. Supervised classification was performed using the maximum likelihood standard algorithm. Normalized Difference Vegetation Index (NDVI) was produced and the health of the wetland vegetation was evaluated. Bioclimatic modeling such as BIOCLIM was used to predict the potential spatial distribution of the wetland species under current and future climatic scenarios. Sea Level Affecting Marshes Model (SLAMM) was used to predict the potential impacts of sea level rise on the coastal wetland communities. A process-based methane emission model that included a productivity factor, temperature dependent (T factor), wetland area, methane flux, precipitation and evaporation ratio was used to estimate the amount of methane emission from the wetlands. The temperature dependent factor was obtained through land surface temperature (LST) estimation algorithms. Measurements of methane fluxes from the wetlands were performed using static chamber techniques and gas chromatography. Geographic Information System (GIS) provided the framework for mapping, modeling and analysis.

This research provides valuable information that could be used by coastal wetland managers in planning and conservation. In order to enhance the conservation of these ecosystems, effective management strategies such as protection and buffering of existing and potentially suitable habitats is recommended. Furthermore, the implementation of efficient mitigation and adaptation strategies of climate change could alleviate the devastating impacts on these sensitive wetland ecosystems.

The study found significant changes in the quality and extent of the coastal wetland communities in the months of September 1989, June 2001 and February 2009. Furthermore, it was found that a rise in mean annual temperature beyond 7oC would likely lead to a complete loss of suitable habitats for the wetland plant species (Avicennia marina, Banksia integrifolia, Melaleuca quinquenervia and Leptospermum liversidgei) in north-eastern NSW. In addition, a meter rise in sea level could decrease coastal wetlands such as inland fresh marshes from about 225.67 km2 in February 2009 to around 168.04 km2 by the end of the century. High variability of methane emission was also found from the coastal wetlands. Forested wetlands produced the highest amount of methane i.e.,0.0016±0.00009 teragrams (Tg) in the month of June, 2001. This would increase to about 0.0022±0.0001 Tg in the month of June with a 1oC rise in mean annual temperature by the year 2030 in north-eastern NSW.

This research provides valuable information that could be used by coastal wetland managers in planning and conservation. In order to enhance the conservation of these ecosystems, effective management strategies such as protection and buffering of existing and potentially suitable habitats is recommended. Furthermore, the implementation of efficient mitigation and adaptation strategies of climate change could alleviate the devastating impacts on these sensitive wetland ecosystems.

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