Land space optimization of urban-agriculture-ecological functions in the Changsha-Zhuzhou-Xiangtan Urban Agglomeration, China

Evaluating urban-agriculture-ecological space is useful in optimizing land space and high-quality socio-economic development. This study evaluated urban development and ecological protection in an urban agglomeration and delineated the ecological security pattern for the sustainable use of land spaces. Using the Changsha-Zhuzhou-Xiangtan (CZT) urban agglomeration as study area, system dynamics (SD) model, cellular automaton (CA), and artificial neural network (ANN) were utilized to simulate the variation trends of urban development space, ecological space, and urban agricultural space for 2019–2035 under different development scenarios (status-quo, economic-centric, environment-centric, and coordinated equilibrium). The highlights of results are as follows: (1) The combined effects of the economy, nature, accessibility, and spillover effects exerted significant impact on urban land expansion. Socio-economic variables and spillover effect constitute the main controlling factors of land space expansion. (2) The urban construction space of the CZT urban agglomeration would vary for the different development scenarios. During the simulation period, urban construction space in the study area would be 1572.06 km2 for the status-quo scenario, 1763.27 km2 for the economic-centric scenario, 1634.13 km2 for the environment-centric scenario, and 1668.69 km2 for the coordinated equilibrium scenario. (3) The growth boundary of the urban agglomeration was demarcated based on the spatial attributes, land-use functions, and clustering. The rigid growth boundary was estimated at 3686 km2, while the flexible growth boundary was estimated to be 1794.53 km2. These values can be used to guide planning, policies, and strategies for the orderly expansion of urban land in future development.