Land use function changes and trade-offs/synergies across topographic gradients in the Three Gorges Reservoir Area, China

Driven by the natural environment and socio-economic development, land use functions (LUFs) experience dynamics and trade-offs/synergies across topographic gradients. This global pattern has a significant impact to the United Nations Sustainable Development Goals. However, there is no direct study investigated the effects of topographical gradients on LUFs trade-offs. Thus, the present study applied an object-based topographical gradient analysis, multi-criteria evaluation, and correlation analysis to evaluate the topographic gradient differentiation in the spatial patterns and characteristic changes in LUFs and their trade-offs/synergies in the Middle Reaches of the Three Gorges Reserve Area (MRTGRA) in China. The findings revealed that: (1) Ecological function (EF) was dominant in the high topographic gradients, whereas production function (PF) and living function (LF) were widely distributed in the low topographic gradients. (2) The changes in LUFs across the topographic gradients experienced a transformation process. Between 1990 and 2000, PF remarkably intensified whereas EF consistently declined across all gradient levels, exhibiting a homogenous LUF change trend across the topographic gradient. Conversely, from 2000 to 2020, PF and LF showed a notable increase at lower topographic gradients, while EF significantly increased at higher gradients, indicating a heterogeneous LUF change trend across the topographic gradient. (3) Trade-offs dominated the relationships between PF and LF, and LF and EF, with decreasing trade-offs between PF and LF as the topographic gradient increases, and weak trade-offs between LF and EF on medium topographic gradients. Similarly, synergies predominantly observed between PF and LF, with a prominent trade-off between PF and EF in high topographic gradients. The findings of present study developed critical considerations for territorial spatial planning, management, and ecological restoration efforts in the MRTGRA and similar hilly and mountainous areas globally.