A simple but actionable metric for assessing inequity in resident greenspace exposure

An increasing number of studies aim to improve and perfect the evaluation system for assessing greenspace exposure, yet it may also become more difficult to apply the evaluation index to landscape planning. Here we propose a simple but actionable index system – Greenspace Exposure Inequity index (GEII), for assessing the inequity of residents' greenspace exposure. GEII includes quantity-based availability, distance-based accessibility, and inequity-based Gini index for assessing the difference in greenspace exposure pattern. Then we selected Shanghai as a case to test the feasibility of GEII, analyzing the spatiotemporal evolution of greenspace exposure patterns, and further demonstrating the operability of the index. (1) Availability inequity for 2012, 2015, 2018, and 2021 was 0.603, 0.512, 0.514, and 0.489. The Gini index was between 0.4 and 0.6, and presented a downward trend. (2) Accessibility inequity for 2012, 2015, 2018, and 2021 was 0.372, 0.368, 0.364, and 0.344. It can be clearly seen that it has changed less over ten years, but overall equality has been rising. (3) Using GEII to calculate the inequity of Shanghai, the Gini index for 2012, 2015, 2018, and 2021 was 0.392, 0.378, 0.373, and 0.357. The inequity of greenspace exposure assessed by GEII is gradually decreasing similarly, which illustrates the positive impact of urban greening policies. The GEII has three highlights: serviceability, human-oriented, and expandability. GEII abandons the complex computational evaluation procedures of numerous indicators and bridges the gap between theoretical research on inequity and practical planning, so GEII is of great value for alleviating the uneven exposure of residents' greenspace and scientifically optimizing landscape planning.