Rice-crawfish map in China

Integrated aquaculture systems, that is, systems involving the cocultivation of aquatic food with crops, provide high protein and energy outputs per unit of land and raise farm incomes. However, they can also cause substantial environmental problems, such as water and soil pollution. We used time series of satellite images to map the evolution of a new farming system integrating paddy rice production with crawfish cultivation from its implementation in 2013 to 2020 in five provinces (805,600 km2) in China. We used an object-based water difference method that integrates pixel-based identification with object-based segmentation. We first mapped the distribution of the water bodies by using the automated water extraction index and then extracted the integrated rice-crawfish area at the pixel level based on changes in the presence of water between the fallow and rice planting periods. We used the noniterative clustering algorithm in GEE to segment the Landsat images. Finally, we intersected the segmentation results with the rice-crawfish pixels and calculated the percentage of crawfish pixels within each image object using 50 % as the threshold for rice-crawfish detection. The object-based water difference method captured integrated rice-crawfish production only when there was a change in the presence of water between the fallow and planting periods. Rice-crawfish farming systems that were not associated with a change in the presence of water could not be identified.