Evaluation and improvement strategies for cooling performance in urban blue-green spaces
Green spaces and water bodies play crucial ecological roles in mitigating the urban heat island ef-fect.However,the limited availability of urban space increases the opportunity cost.This study develops a cooling performance evaluation model based on cost-benefit analysis to quantitatively assess the cooling ef-fects of blue-green space patches of various sizes and types.Using land use and surface temperature data from three periods between 2010 and 2020 in Beijing,the study evaluates the cooling performance and radiation range of blue-green spaces larger than one hectare.The key findings are as follows.First,Over the past decade,the area of blue-green spaces in Beijing has steadily increased,shifting from small areas(1 ≤Ac＜2 hm2)to me-dium(2≤Ac＜10 hm2)and large areas(Ac≥ 10 hm2).While water bodies have increased,the areas of forests,grasslands,and mixed types have decreased.The area within the Third Ring Road has remained largely un-changed,with decreases within the Fourth Ring Road and increases within the Fifth Ring Road.Second,the range of cooling zones for blue-green spaces in Beijing has expanded.Structurally,the cooling zone created by large and medium-sized blue-green spaces is expanding,whereas the cooling area of small blue-green spaces is diminishing.Despite a decrease in forest land area,its cooling zone range has increased,whereas the area of water bodies has grown less than their cooling zones.Third,the performance levels of various blue-green spaces initially increase and then decrease,with small and medium-sized mixed types and large water bodies demonstrating superior cooling performance compared to other scales.Therefore,optimizing the scale and structure of blue-green spaces and rationalizing their spatial layout are crucial for maximizing their cooling ef-fects.This study offers new insights for enhancing the urban ecological environment and promoting sustain-able development.
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