Urban expansion and natural habitat change: Shenzhen as a typical model for China and the developing world

Urban expansion and ecological conservation are central concerns in sustainable urbanization research. While, most cities evolve over centuries, making it hard to capture complete urban-ecological dynamics. One of the most typical cities, Shenzhen, however, underwent an exceptionally rapid transformation from its establishment in 1979 to a highly urbanized metropolis in less than fifty years, providing a rare, complete, and quantifiable case for understanding the urban-ecological dynamic. This study thus integrates theoretical assumption on urban expansion and ecological conservation with long-term Landsat imagery from 1979 to 2024 and landscape pattern indices to explore the spatiotemporal dynamics of urban and ecological spaces in Shenzhen. The results show that the UbS expanded from 35.86 km² to 971.13 km² over 46 years, while forest area decreased from 1437.33 km² to 852.18 km², accompanied by significant losses in farmland and wetlands. These changes reflect a fundamental shift in the city's landscape structure from an "ecology-dominated" system to a "dual urban-ecological" system. Based on quantitative trajectory characteristics, including the growth rates of urban and ecological space and their intersection timing, Shenzhen's districts were classified into three types that are intense-type districts, characterized by continuous urban expansion, severe ecological fragmentation, and habitat loss; stable-type districts, exhibiting consolidated high-density urban patterns with persistent ecological fragmentation; and slow-type districts, defined by limited urban growth, large contiguous ecological cores, and minimal human disturbance. This classification framework reveals the dominant patterns and temporal trajectories of urban-ecological evolutions and provides a context-sensitive methodological reference for development-type delineation and differentiated ecological management in other rapidly urbanzing districts.