Measuring ecological effects and policy mechanisms of urban land use transition – a case study of Xi'an, China

Abstract

ABSTRACT Measuring ecological effects and policy mechanisms of urban Land Use Transition (LUT) is the key to understanding regional environmental changes and achieving sustainable urban developments. This paper illustrates and demonstrates a formal method for measuring the ecological effect of LUT characterized by Ecological Security Index (ESI) and Ecosystem Value (ESV), and enhanced with a correlational analysis between the ecological effect model and urban policy mechanism. Using Xi'an, a major capital city of western China as a case study, based on multi-temporal Thematic Mapper (TM) remote sensing images, Digital Elevation Model (DEM) and relevant statistical data, the results show that the method using ESI and ESV, together with the Land Use Transition Probability Matrix (LUTPM) can comprehensively measure the ecological effects of LUT process in Xi'an from 2000 to 2020. The results show that due to the impact of urban expansion, regional construction land increased significantly (by 67.07%), while farmland decreased considerably (by 13.12%). The farmland and forestland around the main urban area of Xi'an were centrally converted into construction land, yet the mutual transition of other types of land was relatively scattered. The total amount of ESV has slightly increased from 40.1 billion yuan to 42.8 billion yuan, and the proportion of ecological service function value presents a decreasing trend in regulation function (65%), support function (22%), supply function (9%), and cultural function (4%). The ESI value slightly decreased from 0.517 to 0.512, and overall it is still in a state of ecological security. The trend of ESV and ESI decreasing from mountainous areas to plains indicates that high-intensity human activities in plain areas have had a significant impact on the ecological environment. The correlation analysis between policy mechanisms and ecological effects indicates that ecological protection policies have improved the ecological environment and maintain ecological security (high ESV-high ESI mode), and may also have limited economic activities and been detrimental to the security of urban composite ecosystems (high ESV-low ESI mode). Spatial expansion policies have driven the rapid growth of construction land and threatened ecological security (low ESV-low ESI mode). Zoning adjustment policies have led to the transformation of ecological land to construction land, threatening ecological security and reducing ESV (low ESV-low ESI mode), and may also have promoted industrial upgrading and economic development, providing economic assurance for improving ecological security (low ESV-high ESI mode). These comprehensive findings provide valuable insights for understanding the ecological effects and policy mechanisms of LUT in Xi'an for achieving sustainable urban development, and demonstrate and explore a novel method to more appropriately and effectively measure LUT by combining ESV and ESI.