Understanding the dynamics of integrated rice-crawfish farming in Qianjiang county, China using Landsat time series images

CONTEXT: The emerging integrated rice-crawfish (IRC) farming system, combining paddy rice cultivation with crawfish production, has recently expanded rapidly in central China because of its high efficiency and profits. To date, research on the IRC system has mainly focused on its ecological environmental effects using either statistics or field-point data without spatial and temporal attributes. OBJECTIVE: The objective of this study was to address how IRC can be accurately mapped considering its phenological features, and what spatiotemporal dynamics of IRC occurred in Qianjiang in 2013-2018. METHODS: Based on the phenology of IRC, we used an object-based water difference method (OWDM) to map its spatial distribution in Qianjiang in 2013-2018, and then analyzed the spatiotemporal dynamics of IRC in terms of its distribution, field sizes, and under different farming systems. RESULTS AND CONCLUSIONS: Results show that the OWDM performs well with overall accuracy greater than 92%. The IRC area continuously increased from 1500 ha in 2013 to 27,600 ha in 2018. Spatially, IRC was initially concentrated in southwestern Qianjiang, but later expanded to the northwestern region. The field size has become larger as IRC has extended to all regions, ranging from 0.5 ha to over 10 ha. The state-owned farming system has played an important role in leading the IRC development, growing rapidly in 2013-2015 and then gradually stabilizing. By comparison, IRC in smallholder farming regions accelerated in the later period, increasing steeply by 18,700 ha in 2018, which is double that of the state-owned farming system. SIGNIFICANCE: This study provides an efficient mapping approach and basic information of IRC spatial dynamics, which help understand its developmental processes, optimize resource allocation, facilitate management, and further explore the effects of IRC.

Automated summary

The study focused on accurately mapping the phenological features of the IRC system in Qianjiang from 2013 to 2018, and analyzed the spatiotemporal dynamics. Results showed that the IRC area continuously increased over the years, with different farming systems influencing the development speed.