The causes of farmland landscape structural changes in different geographical environments.

Farmland landscapes are intuitive indicators of the functions of farmland ecosystems. However, geographical differences complicate the spatio-temporal evolutionary characteristics of farmland landscape systems, making them difficult to explore. This creates a series of difficulties in designing farmland management policy in China's diversified geographical environment. This study aims to explore the evolution of laws and dynamic mechanisms of farmland landscape structural changes in different geographical environments at the provincial level in China. A landscape structure classification model at the pixel level was developed using the principles of range attenuation in geographical space and ecological boundary effects to identify the spatial characteristics of the degradation processes in farmland landscapes. A redundancy analysis (RDA) investigated the human and natural causes of farmland landscape degradation processes. The results demonstrate that the farmland landscape systems in Jiangsu Province degraded between the 1980s and 2010 on a spatial gradient with human geography: the beginnings of industrialisation → rapid industrialisation → completion of industrialisation. Degradation manifested temporal and spatial differentiation as follows: fragmentation via the joint activities of invasion from non-agricultural boundaries and internal wedging → fragmentation caused by non-agricultural internal wedging → fragmentation caused by boundary invasion. The core causal factors of degradation were development intensity and the extent of construction land, which indicate changes in socioeconomic development. Industrialisation and rapid urbanisation increased the development intensity of human construction, which disrupted the connections among farmland landscapes through boundary invasions or discontinuous occupations. This subsequent fragmentation of farmland landscape patterns degraded the productive and ecological functions of farmlands. This study indicates that development intensity around agricultural environments should be strictly controlled which would be beneficial for the design of farmland conservation policies and land management in China.