Scenarios and sustainability of the economy-nitrogen-resource-environment system using a system dynamic model on the Qinghai-Tibet Plateau.

ABSTRACT

Nitrogen (N) plays a vital role in the development of crop production and animal husbandry in agricultural and pastoral areas. However, the irrational utilization of N resources and subsequent environmental issues with rapid economic development has attracted wide public attention. Coordinating the economy-N-resource-environment (ENRE) system is of great importance for regional sustainable development. In this study, the dynamics of the ENRE system of a typical agricultural and pastoral area on the Qinghai-Tibet Plateau (QTP) were simulated using the VENSIM software from 1998 to 2018. Four typical scenarios (current development scenario, economic development scenario, environment protection scenario and resource optimization scenario) are established to assess the sustainability level and the coupling coordination degrees (CCDs) of the three subsystems, i.e., the economy, N-resource and environment subsystems from 2019 to 2030. Our study indicates that the N flow-based system dynamics (SD) model connects the different subsystems of the ENRE system together well and allows different scenario simulations. From 2019 to 2030, the ENRE system is at a weak sustainability level during the simulation period, and the three subsystems are at slightly unbalanced stages of development in terms of CCD level. The sustainability and CCD levels of the four examined scenarios are as follows resource optimization scenario > economic development scenario > environment protection scenario >current development scenario, with average values of 0.45, 0.37; 0.42, 0.36; 0.41, 0.35; and 0.39, 0.34, respectively. Under the resource optimization scenario, reducing N inputs to food production and consumption and reducing the planting area of cash crops can effectively improve the N use efficiency of the food chain in the N-resource subsystem (15.34% from 2019 to 2030 on average). Our results provide a reference for promoting sustainable development and formulating policies in agricultural and pastoral regions.