In the 1930’s the Federal Home Loan Bank Board established a program to appraise real estate risk levels in several cities. Four classes indicating level of security for real estate investments were developed: A (green) – best, B (blue) – still desirable, C (yellow) – declining, and D (red) – hazardous. Recent studies have shown that heat island effects are greater, imperviousness is higher, and tree cover lower in areas that were formerly redlined (class D). This paper analyzed all redlined areas in U.S. cities and confirms that redlined areas (class D) have lower tree cover, greater impervious cover and lower forest ecosystem service values than other classes, with tree cover declining and impervious cover increasing as security risk class increased. Nationally, tree cover averaged 40.1 percent in class A and 20.8 percent in Class D; impervious cover averaged 30.6 in Class A and 53.0 percent in Class D. Loss of annual ecosystem services in riskier redlined areas (classes B-D) compared to the highest rated zone (class A) conservatively equates to $308 million nationally if classes B-D had the percent tree cover exhibited in Class A. At the city scale, these losses in foregone services can reach up to $100 million per year (New York, NY). As percent tree cover and percent tree cover stocking declines as percent impervious cover increases, differences in the physical impervious structure of the redlined areas at the time of designation influence tree cover differences. As redlined areas were often delimited in areas with higher population density and impervious cover, these areas tend have lower tree cover today. Even if stocking levels were increased to levels exhibited in Class A (57.8%) among all classes, tree cover would still decrease as class risk increases due to less available greenspace in lower graded classes. These patterns illustrate the importance of impervious cover on the distribution of ecosystem services and understanding the impacts of redlining practices. City policies could be directed to help offset these disparities by enhancing tree cover and reducing impervious cover in these under-resourced areas.

在 1930 年代，联邦住房贷款银行委员会制定了一项计划来评估几个城市的房地产风险水平。开发了四个等级来指示房地产投资的安全级别：A（绿色）-最好，B（蓝色）-仍然可取，C（黄色）-下降，D（红色）-危险。最近的研究表明，在以前的红线区域（D 级），热岛效应更大，不透水性更高，树木覆盖率更低。本文分析了美国城市的所有红线区域，并确认红线区域（D 级）的树木覆盖率较低，不透水覆盖率较高，森林生态系统服务价值低于其他等级，随着安全风险等级的增加，树木覆盖率下降，不透水覆盖率增加。在全国范围内，A 类树木覆盖率平均为 40.1%，D 类树木覆盖率为 20.8%；不透水覆盖率在 A 类中平均为 30.6%，在 D 类中为 53.0%。如果 BD 类具有树百分比，则与最高评级区域（A 类）相比，风险较高的红线区域（BD 类）的年度生态系统服务损失保守地相当于全国 3.08 亿美元封面展示在 A 级。在城市规模上，这些已放弃服务的损失每年可高达 1 亿美元（纽约州纽约市）。由于树木覆盖率和树木覆盖率放养百分比随着不透水覆盖率的增加而下降，指定时红线区域的物理不透水结构的差异会影响树木覆盖率的差异。由于红线区域通常被划定在人口密度较高和不透水覆盖率较高的地区，因此这些地区如今的树木覆盖率往往较低。即使放养水平提高到所有班级的 A 级水平（57.8%），由于较低等级班级的可用绿地较少，树木覆盖率仍会随着班级风险的增加而减少。这些模式说明了不透水覆盖对生态系统服务分布的重要性以及了解红线做法的影响。可以指导城市政策通过在这些资源不足的地区增加树木覆盖和减少不透水覆盖来帮助抵消这些差异。