Urban tree cover contributes to human well-being through a variety of ecosystem services. In this study, we focus on the role that trees can play in reducing temperature during warm seasons and associated impacts on human health and well-being. We introduce a method for quantifying and valuing changes in premature mortality from extreme heat due to the changes in urban tree cover and apply this method to Baltimore City, Maryland. The model i-Tree Cool Air uses a water and energy balance to estimate hourly changes in air temperature due to alternative scenarios of tree cover applied across 653 Census Block Groups. The changes in temperature are applied to existing temperature–mortality models to estimate changes in health outcomes and associated values. Existing tree cover in Baltimore is estimated to reduce annual mortality by 543 deaths as compared to a 0% tree cover scenario. Increasing the area of current tree cover by 10% of each Census Block Group reduced baseline annual mortality by 83 to 247 deaths (valued at $0.68 –2.0 billion applying Value of Statistical Life estimates). Over half of the reduced mortality is from the over 65 year age group, who are among the most vulnerable to extreme heat. Reductions in air temperature due to increased tree cover were greatest in downtown Baltimore where tree cover is relatively low and impervious cover is relatively high. However, the greatest reductions in mortality occurred in the outskirts of Baltimore where a greater number of people who are over 65 years in age reside. Quantifying and valuing the health benefits of changes in air temperatures due to increased tree cover can inform climate adaptation and mitigation plans by decision makers. Developing adaptation strategies to effectively address these issues will become increasingly important in the future under changing climates and an aging population.

城市树木的覆盖物通过各种生态系统服务为人类的福祉做出了贡献。在这项研究中，我们重点研究树木在温暖季节可以起到的降低温度的作用，以及对人类健康和福祉的相关影响。我们引入了一种量化和评估由于城市树木覆盖率变化而导致的极热导致过早死亡的变化的方法，并将该方法应用于马里兰州的巴尔的摩市。i-Tree Cool Air模型使用水和能量平衡来估算每小时的气温变化，这是由于在653个人口普查组中应用了树木遮盖的替代方案所致。温度的变化将应用于现有的温度-死亡率模型，以估计健康结果和相关值的变化。与0％的树木覆盖率情景相比，巴尔的摩现有的树木覆盖率估计可使每年的死亡率降低543例死亡。每个普查区块组将当前树木的覆盖面积增加10％，可以将基线年死亡率降低83例至247例死亡（按统计生命值估算，价值为0.68至20亿美元）。降低的死亡率中有一半以上来自65岁以上的年龄段，他们是最容易遭受极端高温伤害的人群。在巴尔的摩市中心，树木覆盖率相对较低，而防渗覆盖率则相对较高，这是由于树木覆盖率增加导致的气温下降最大。但是，死亡率下降最大的地区是巴尔的摩郊区，那里居住着更多的65岁以上的人。量化和评估因树木覆盖增加而引起的气温变化所带来的健康益处，可以为决策者提供适应气候变化和减缓气候变化的计划。在气候变化和人口老龄化的情况下，制定适应策略以有效解决这些问题在未来将变得越来越重要。