Increases in the intensity and frequency of tropical cyclones due to changing climatic conditions are threatening sea turtle nesting beaches. The iSimangaliso Wetland Park Sea turtle nesting beach is located along the coast in northeastern KwaZulu-Natal, South Africa. Nevertheless, the impact of these tropical cyclones on the iSimangaliso Wetland Park sea turtle beach remains uncertain.
Landsat 7 and 8 medium-resolution multispectral satellite images were also collected from the USGS and used in the Digital Coastal Analysis System to calculate changes in shoreline position along the iSimangaliso Wetland Park sea turtle nesting area caused by tropical cyclones. The results show that: (1) tropical cyclone intensity within 1000 km of the iSimangaliso Wetland Park sea turtle nesting beach increased by 13.80% from 1980 to 2020. Overall, these results show that unlike other nesting beaches sea turtles, the sea turtle nesting beach at iSimangaliso Wetland Park is relatively safe from tropical cyclone activity despite rapidly rising sea surface temperatures.
Future research should consider using higher resolution satellite or drone and lidar imagery to study shoreline changes associated with tropical cyclone activity and possible sea level rise along the sea turtle nesting beach in the iSimangaliso Wetland Park.
PLAGIARISM
PUBLICATIONS AND MUNUSCRIPTS
Chapter
- Impact of tropical cyclones in Context
- Aim
- Objectives
- Motivation
- The study area
- Climate
- Ocean Currents
- Vegetation
- Shoreline Characterisation
Chapter
- Abstract
- Introduction
- Materials and methods
- Study area
- Data acquisition and processing
- Storm clustering Distance calculation
- Construction of space-time cubes
- Analysis of local outliers
- Analyzing the Emergence of tropical cyclone Hot and Cold Spots
- Results
- Tropical cyclone intensities
- Space-time cube analysis of tropical cyclone frequency
- Local Outlier analysis
- Emerging Hot and Cold Spots of tropical cyclone frequency
- Discussion
- tropical cyclone Intensities
- Tropical cyclone frequency
- Patterns of tropical cyclone clusters
- Conclusions
20 Figure 2.3 The Local Outlier analysis of Tropical Cyclone clusters within 1000 km of the iSimangaliso Wetland Park in ArcMap 10.6. 23 Figure 2.4 Emerging hot and cold spots from tropical cyclones within 1000 km of the iSimangaliso Wetland Park sea turtle nesting beach in ArcMap 10.6. As a result, the threat that tropical cyclones pose to the health of the iSimangaliso Wetland Park sea turtle nesting beach remains unclear.
This research aims to assess the effects of tropical cyclones on the iSimangaliso Wetland Park sea turtle nesting beach using geospatial technologies. To analyze the impact of changing climatic conditions on the intensity of tropical cyclones within 1000 km of the coast of the iSimangaliso Wetland Park sea turtle nesting beach from the year 1980 to 2020. In general, only 5% of tropical cyclones form in the southwest Indian Ocean come ashore (Reason & Keibel, 2004).
A space–time cube is used in this study to analyze the spatiotemporal distribution of tropical cyclones within 1000 km of the coast of the iSimangaliso Wetland Park sea turtle nesting beach. In this study, the Emerging Hot Spot tool is used to analyze the spatiotemporal frequency of tropical cyclones within a 1000 km of the coast of the iSimangaliso Wetland Park sea turtle nesting beach. The results of the Emerging Hotspot analysis (Table 2.3) show the spatiotemporal clustering patterns of tropical cyclones within 1000 km of the coast of the iSimangaliso Wetland Park sea turtle nesting beach.
This study found that the intensity of tropical cyclones within 1000 km of the coast of the iSimangaliso Wetland Park sea turtle nesting beach increased by 13.80% from 1980 to 2020. A spatial analysis of the intensity and frequency of tropical cyclones near the iSimangaliso Wetland Park sea turtle nesting beach was successfully carried out using Space-time pattern mining tools.
Chapter
- Abstract
- Introduction
- Materials and methods
- Study Area
- Data and pre-processing ..................................................................................... 3-39
- Shorelines change calculation
- Error Assessment
- Statistical Analysis of tropical cyclone Variables
- Results
- The distance of shoreline change
- The rate of shoreline change
- Correlation analysis between tropical cyclone variables and rate of Shoreline
- Error Assessment
- Discussion
- The Impact of Tropical Cyclones on Shoreline Change
- Conclusion
The sea turtle nesting beach at iSimangaliso Wetland Park is a key rookery for leatherback and karate sea turtles. The Digital Coastal Analysis System was then used to analyze spatio-temporal changes in shoreline position along the sea turtle nesting beach of iSimangaliso Wetland Park. Overall, the sea turtle nesting beach at iSimangaliso Wetland Park is currently increasing as evidenced by the seaward progression of the shoreline across the study area.
The iSimangaliso Wetland Park is a critical wood and leatherback sea turtle nesting beach in South East Africa (10-11). Consequently, no study has analyzed the statistical relationship between tropical cyclone frequency and intensity on the rate of shoreline change on sea turtle nesting beaches. 3] To conduct a correlation analysis between tropical cyclone intensities and frequency with linear shoreline change rates along the iSimangaliso Wetland Park sea turtle nesting beach.
The sea turtle nesting beach of Simangaliso Wetland Park also experiences episodic flooding and erosion due to tropical cyclones (23). The data were cropped using a buffer of 1000 km offshore of the iSimangaliso Wetland Park sea turtle nesting beach in ArcMap 10.6. The average distance of shoreline changes between 1999 and 2020 along the sea turtle nesting beach of Simangaliso Wetland Park was 31.09 m.
Therefore, the positive shoreline changes in Figure 3.3 indicate that the sea turtle nesting beach in the study area is primarily seaward accretionary/migratory. Rates of shoreline change along the iSimangaliso Wetland Park sea turtle nesting beach were measured using endpoint rate (EPR) and linear regression rates (LRR) statistics, respectively. In section 3.2.5 the main sources of error associated with the methodology and data used in this study were identified and include pixel error, georeferencing error, and error associated with deriving the normalized shoreline-weighted water index ( Table 3.3).
These results indicate that sea turtle nesting beaches are increasing despite regional increases in tropical cyclone intensity. A variety of factors contribute to shoreline change along the sea turtle nesting beach at iSimangaliso Wetland Park. In summary, the results of this study show that between 1999 and 2020, the sea turtle nesting beach in iSimangaliso Wetland Park increased despite the threat of tropical cyclones.
Therefore, if the frequency of tropical cyclones along the southwest Indian Ocean increases, the sea turtle nesting beach of Simangaliso Wetland Park may begin to experience inshore retreat.
Chapter
- Introduction
- Summary assessment of the results
Tropical cyclones are associated with damaging weather conditions that can destroy sea turtle eggs in sandy coastlines. Tropical cyclones increase wave heights, wind speeds and flooding, which can flood or expose sea turtle nests. In the southwestern Indian Ocean, the sharp rise in sea surface temperatures has increased the intensity of tropical cyclones, however making it uncertain how these changing oceanic conditions have affected the frequency of tropical cyclones.
Sea turtle nesting beach iSimangaliso Wetland Park located adjacent to this southwestern Indian Ocean is a critical nesting beach for loggerhead and leatherback sea turtles in Southern Africa. Therefore, it was essential to assess the extent to which the frequency and intensity of tropical cyclones near this study area are responding to the effects of climate change (Chapters 2 and 3). It was also essential to assess the extent to which tropical cyclones are causing shoreline variability in the study area.
Geospatial tools such as the Space-Time Pattern Mining and the Digital Shoreline Analysis tools in ArcGIS 10.6 software provide a simple yet effective methodology for analyzing and quantifying Tropical Cyclone-induced coastal erosion. In South Africa, this is even more important as it provides a simple yet cost-effective method to assess the long-term health of the iSimangaliso Wetland Park sea turtle nesting beach. To determine whether the frequency of tropical cyclones along the iSimangaliso Wetland Park sea turtle nesting beach has increased from the year 1980 to 2020 due to changing climate conditions.
To assess the degree to which the sea turtle nesting coastline of iSimangaliso Wetland Park is retreating due to tropical cyclones. To determine the statistical relationship between shoreline movement rates and tropical cyclone intensity and frequency at the sea turtle nesting beach at iSimangaliso Wetland Park.
To analyze the impact of changing climatic conditions on the intensity of
To determine whether the frequency of Tropical Cyclones adjacent to
The study successfully analyzed the spatio-temporal trend of tropical cyclones within 1000 km of the coast of the sea turtle nesting beach of iSimangaliso Wetland Park (Chapter 2). The results in Chapter 2 showed that tropical cyclones near the sea turtle nesting beach in iSimangaliso Wetland Park show a non-significant spatio-temporal trend (z = 0.56 and p = 0.58 (>.05). This means that despite the changing climate and increasing sea surface temperatures, the frequency of tropical cyclones has remained relatively stable over the years.
A possible reason for this was the strengthening of the Hadley cell in the subtropics, which displaces the subtropical jet stream and thus reduces the number of tropical cyclones that form each year (Chapter 2 section 2.6). The results in Chapter 2 contradict most global climate models that postulate that tropical cyclones will increase as a result of climate change along the southwestern Indian Ocean.
To assess the degree to which the iSimangaliso Wetland Park sea turtle
To determine the statistical relationship between the rates of Shoreline
Limitations
Another limitation of the study was the presence of cloud cover particularly in the Landsat 8 images, which limited the ability to accurately detect shoreline positions. As such, some Landsat images for October, the month of the beginning of the nesting season, could not be used. In addition, there may have been some uncertainty in estimating the position of the coastline from satellite images due to uncertainties related to tidal conditions, pressure regime, beach slope, high erosion, seasonal and multiannual variations in oceanic climates. (Smith et al., 2016).
Finally, according to Smith et al. 2016), the southeastern coastline of Africa shows an 18-year cycle of erosion. Erosion rates along the study area show an 18-year cycle of high and low rates, so since this study only covers 22 years, it may only show half of the erosion cycle of the study area.
Recommendations and directions for future research
- Recommendations
- Directions for future research
It may be important for future studies to extend the study period from 22 years to 36 years to account for the 18-year erosion cycle along the eastern coast of South Africa. Despite this study's success in analyzing the impact of tropical cyclones on the iSimangaliso Wetland Park, radiometric errors on the satellite images were a setback. Therefore, future studies should use drone imagery with high spatial and temporal resolution to improve the accuracy of shoreline positions.
A perspective on sea level rise and coastal storm surge from southern and eastern Africa: A case study near Durban, South Africa.
