Redai dili (May 2021)
Spatial-Temporal Changes in Aquaculture Ponds in Coastal Cities of Guangdong Province: An Empirical Study Based on Sentinel-1 Data during 2015-2019
Abstract
Guangdong Province has the largest extent of coastal aquaculture in China. Quantitative analysis of the spatial distribution pattern and evolution trend of on-land artificial aquaculture bases in the coastal areas of Guangdong Province has great significance for exploring the sustainable development approach of freshwater aquaculture in the region. Based on the Google Earth Engine cloud computing platform, Sentinel-1 SAR imagery, and other data, this study extracted the artificial aquaculture bases of the 14 coastal cities in Guangdong Province from 2015 to 2019 using an object-oriented method, implemented quantitative analysis on its spatial distribution trend and high-density distribution area, and analyzed the relationship between these aquaculture bases and city economic growth. The classification results of the regular artificial aquaculture bases in this study showed that the extraction of aquaculture bases based on radar remote sensing imagery had high accuracy, with an overall accuracy of 90.5% and a kappa coefficient of 0.81. The results also showed that the total area of artificially regulated aquaculture bases in Guangdong Province had an upward trend from 2015 to 2019, with a net increase of 163.1 km2. The three cities with the largest net area growth were Jiangmen, Zhongshan, and Guangzhou. Using a grid with 1 km resolution to study the density dynamics, the density of aquaculture land in most areas was found to have increased, especially in high-density areas. Among these, 80% of the artificial aquaculture bases were concentrated within 5 km of the coastline, and the bays and river inlets had the highest densities and largest areas of aquaculture land. A comparison of the distribution patterns among different cities showed that the cities with the most concentrated aquaculture land within the land boundary were Shantou, Chaozhou, Zhuhai, Zhongshan, Shenzhen, Zhanjiang, and Yangjiang, followed by Shanwei, Guangzhou, Jieyang, and Jiangmen, and that Maoming, Dongguan, and Huizhou were the least concentrated. In terms of economy, the proportion of aquaculture industry in the regional GDP declined in more than half of the cities, increased in only Yangjiang, and remained unchanged in the others. In addition to the fact that Guangdong Province's economic development focuses on secondary and tertiary industries, this result may also be related to the government's ongoing ecological restoration actions, which have restricted aquaculture land use. In general, aquaculture land in the coastal cities in Guangdong Province showed an overall trend of expansion. Moreover, the growth in area of regular aquaculture bases showed a significant correlation with the value of aquaculture production, further indicating that land expansion of artificial aquaculture bases continued to be the main method for increasing the value of aquaculture production in Guangdong Province. Such an expansion trend poses a great challenge to the distribution and sustainable use of wetlands, cropland, and urban land in the coastal zone.
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