Abstract
Asia is the major contributor to global aquaculture production in quantity, accounting for almost 90%. These practices lead to extensive land-use and land-cover changes in coastal areas, and thus harm valuable and sensitive coastal ecosystems. Remote sensing and GIS technologies contribute to the mapping and monitoring of changes in aquaculture, providing essential information for coastal management applications. This study aims to investigate aquaculture expansion and spatio-temporal dynamics in two Chinese river deltas over three decades: the Yellow River Delta (YRD) and the Pearl River Delta (PRD). Long-term patterns of aquaculture change are extracted based on combining a reference layer on existing aquaculture ponds for 2015 derived from Sentinel-1 data with annual information on water bodies extracted from the long-term Landsat archive. Furthermore, the suitability of the proposed approach to be applied on a global scale is tested based on exploiting the Global Surface Water (GSW) dataset. We found enormous increases in aquaculture area for the investigated target deltas: an 18.6-fold increase for the YRD (1984–2016), and a 4.1-fold increase for the PRD (1990–2016). Furthermore, we detect hotspots of aquaculture expansion based on linear regression analyses for the deltas, indicating that hotspots are located in coastal regions for the YRD and along the Pearl River in the PRD. A comparison with high-resolution Google Earth data demonstrates that the proposed approach can detect spatio-temporal changes of aquaculture at an overall accuracy of 89%. The presented approach has the potential to be applied to larger spatial scales covering a time period of more than three decades. This is crucial to define appropriate management strategies to reduce the environmental impacts of aquaculture expansion, which are expected to increase in the future.
Highlights
One major land-use and land-cover change of the last decades in coastal areas can be attributed to the expansion of aquaculture
Around 80% and 63% of aquaculture ponds in the Yellow River Delta (YRD) and the Pearl River Delta (PRD) respectively by the Sentinel-1 Aquaculture Layer could be detected by the combined approach with Landsat
When considering the aquaculture area, numbers increase to 95% for the YRD and 81% for the PRD, which indicates that agreement between the two approaches improves, for large ponds
Summary
One major land-use and land-cover change of the last decades in coastal areas can be attributed to the expansion of aquaculture. Aquaculture defines any sort of aquatic organisms farmed and harvested in aqua farms, which are almost exclusively destined for human food consumption [1]. The majority of aquaculture is farmed in inland aquaculture basins, accounting for 63% of global production [1]. Aquaculture is the sector of food production systems with the highest growth rates. Several studies pointed out that aquaculture has the potential to reduce poverty across the world [2,3,4]. Aquaculture as a controlled system of protein production is powerful in contributing to food security and covering future nutrition demands, which positively influences human well-being [5,6]
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