Abstract
Mulberry-dyke-fish pond ecosystems are a representative traditional eco-agriculture in the Guangdong–Hong Kong–Macao Greater Bay Area (GBA). Investigations about the changes in the systems and their relevant water environments under the background of rapid urbanization can provide valuable information to formulate sustainable protection and development strategies. Using the Landsat images obtained after 1986, this study combined supervised classification and visual interpretation approaches, as well as water intensity index and synthesized index to identify the spatial patterns of changes in the ponds in the GBA over the past 40 years. The results indicated that during the period 1986–2013, the total surface area of the ponds in the GBA increased significantly and peaked in 2013 with a total increase of 84.63%; After that, the total surface area showed a downward trend with a total decrease of approximately 31.34%. The year of 2013 was identified as the milestone of the changes. The results proved that human activities have continuously influenced the spatial distribution and size of fish ponds in the past 40 years. The fish ponds had transformed from near-natural ponds with different sizes and a near-natural random distribution in the early stage into an artificial distribution and an artificial shape. Land use changes, industrial transfer, Government guidance and financial motives were the major drivers to the changes. If no effective measures are taken, this shrinking trend in the ponds will remain in the future.
Highlights
The results proved that human activities have continuously influenced the distribution and size of fish ponds in the past 40 years
It is expected that the development of measurements of standard deviation, coefficient of variation, Theil coefficient, water body fish ponds will tend to integrate with the tourism and service industry
From 1986 to 2019, the fish ponds in the Greater Bay Area (GBA) showed an overall increasing trend in ponds construction traditionaltrend aquacultural demonstration areas
Summary
Compared to other agricultural systems, this system has better economic and ecological performance, with advantages in regulation of droughts and floods, stable high outputs, and easy operation [2] This traditional agriculture system is believed under a crisis of extinction caused by the outflow of rural population and the fast expansion of cities and towns, especially in the GBA, which now is one of the most prosperous regions in China. Compared with other large waterbodies, ponds are less capable of pollutant dilution, leading them to be abandoned Under these circumstances, there have been increasing awareness to implement conservation policies for the pond ecosystem preservation. Previous studies on the ponds in the GBA mainly focused on its ecological functions, such as applications of energy theories to make synthetical and quantitative analyses based on energy structure and indices [1] Their historical development, agricultural heritage and landscape patterns were investigated. Influencing factors were analyzed to provide an accurate reference for decision making on pond ecosystem restoration and conservation
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