Our objectives were to synthesize the early evidence regarding the effect of city-wide vacant-lot remediation programs on firearm violence and to determine what proportion of remediation costs are recovered from reducing firearm violence. Building on our scoping review, we conducted a meta-analysis of before-and-after studies with control groups. We then assumed three hypothetical cities of small, medium, and large populations and performed a probabilistic benefit-to-cost analysis over 30 years.

Eight studies met our eligibility criteria. Interventions included mowing (n = 3), greening (n = 5), and gardening (n = 2), with two studies examining two different interventions. The pooled effect size did not show reduction in firearm violence by mowing vacant lots. However, greening and gardening interventions reduced firearm violence by 5.84% (95% CI: 7.89–3.79%) and 5.34% (95% CI: 7.74–2.93%) respectively. Greening programs were the most cost-effective intervention and cost savings from reducing firearm violence can recover an estimated 8.17% (95% CI: 8.11–8.23%), 10.20% (95% CI: 10.12–10.28%), and 21.06% (95% CI: 20.90–21.23%) of intervention expenses, equating to the net annual per capita costs of $64.53 (95% CI: $64.09–$64.96), $51.88 (95% CI: $51.53–$52.25), and $30.97 (95% CI: $30.73–$31.22) in the small, medium, and large cities respectively.

While vacant lot remediation programs can play a robust role in controlling firearm violence at lower per capita costs than law enforcement polices, cost savings from reducing firearm crimes by itself does not recover all program costs. However, health and environmental benefits of such programs can offset the greening and maintenance costs.

我们的目标是综合有关全市空地补救计划对枪支暴力影响的早期证据，并确定从减少枪支暴力中回收的补救成本比例。在我们的范围审查的基础上，我们对对照组的前后研究进行了荟萃分析。然后，我们假设了三个拥有小、中、大人口的假设城市，并进行了 30 年的概率收益成本分析。

八项研究符合我们的资格标准。干预措施包括割草 (n = 3)、绿化 (n = 5) 和园艺 (n = 2)，两项研究检验了两种不同的干预措施。合并效应大小并没有显示通过修剪空地来减少枪支暴力。然而，绿化和园艺干预措施分别将枪支暴力减少了 5.84%（95% CI：7.89–3.79%）和 5.34%（95% CI：7.74–2.93%）。绿化计划是最具成本效益的干预措施，减少枪支暴力所节省的成本估计可以恢复 8.17% (95% CI: 8.11–8.23%)、10.20% (95% CI: 10.12–10.28%) 和 21.06% ( 95% CI：20.90-21.23%）的干预费用，相当于每年净人均成本 64.53 美元（95% CI：64.09-64.96 美元）、51.88 美元（95% CI：51.53-52.25 美元）和 30.97 美元（95% CI：51.53-52.25 美元） ：30.73 美元至 31.22 美元）在小型、中型、

虽然空地补救计划可以以低于执法政策的人均成本在控制枪支暴力方面发挥强大的作用，但仅靠减少枪支犯罪而节省的成本并不能收回所有计划成本。然而，此类计划的健康和环境效益可以抵消绿化和维护成本。