Spatiotemporal patterns of urbanization over the past three decades: a comparison between two large cities in Southwest China

China’s economic development over the past three decades has been remarkable due to the establishment of the “Reform and Opening-up” program. Meanwhile, urbanization, one of the most intensive human activities, has significantly changed the land cover across China. Here we used remote sensing data and landscape metrics to explore the spatiotemporal patterns of urbanization in two large Chinese cities, Chengdu (1978–2010) and Chongqing (1976–2010). Results suggested that urban land in both cities experienced a significant growth and became 9.8 and 6.3 times larger than the initial for Chengdu and Chongqing, respectively. The edge-expansion was the major urban growth form for both cities, accounting for more than 40 % of total three types (i.e., edge-expansion, infilling, and outlying) although fluctuating during the whole period. Both cities started a spurt growth in the 1990s although the starting times were different (1992 and 1996 for Chengdu and Chongqing, respectively) because of different policies. Spatial distribution of the newly developed urban lands was largely constrained by topography. Landscape analysis not only revealed an increasing fragmentation and complexity in the study area under the impact of urbanization, but also tested the hypothesis on urbanization patterns.