Informal green spaces (IGS) such as overgrown vacant lots and urban brownfields constitute a considerable amount of green resources in the city. Given that the increasingly competitive land use of the urban area, enhancing the potential ecosystem services (ES) of IGS through design and management practices is of critical importance. This literature review paper provides an overview of ES delivered by urban IGS: What types of IGS have been discussed? Which ES have been identified in IGS, what interrelationships among different types of ES have been identified, and how can the potential of IGS be enhanced by urban design practices? 112 scientific papers were analyzed for their 1) IGS terms applied, 2) ES studied, 3) current or potential ES discussed, 4) ES trade-offs, and 5) ES assessment methods. Through the review, we found that although different types of ES have been identified in IGS, most studies did not consider ES synergies and trade-offs. The few studies assessing trade-offs of ES in IGS mostly focused on large-scale IGS such as urban brownfields rather than on small-scale IGS such as vacant lands/lots. The literature review highlights two knowledge gaps for future research: the first one is to explore the design and management knowledge that integrate multiple ES in small-scale IGS based on the assessment of potential ES trade-offs and synergies; the second one is to develop the spatial assessment of ES trade-offs and synergies, which is the key to envision design and management interventions that optimize the benefits of IGS. The literature review promotes the acknowledgement of the term IGS through highlighting their value in ES provisioning and further outlines future research directions on small-scale IGS such as vacant lands/lots and patches of spontaneous vegetation.

杂草丛生的空地和城市棕地等非正式绿地 (IGS) 构成了城市中相当多的绿色资源。鉴于城市地区土地利用竞争日益激烈，通过设计和管理实践增强 IGS 的潜在生态系统服务 (ES) 至关重要。这篇文献综述论文概述了城市 IGS 提供的 ES：讨论了哪些类型的 IGS？IGS 中确定了哪些 ES，已确定不同类型 ES 之间的相互关系，以及城市设计实践如何增强 IGS 的潜力？分析了 112 篇科学论文的 1）应用的 IGS 术语，2）研究的 ES，3）讨论的当前或潜在的 ES，4）ES 的权衡，以及 5）ES 评估方法。通过审查，我们发现，尽管 IGS 中已经确定了不同类型的 ES，但大多数研究并未考虑 ES 的协同作用和权衡。为数不多的评估 IGS 中 ES 权衡的研究主要集中在城市棕地等大型 IGS，而不是空地/地块等小型 IGS。文献综述突出了未来研究的两个知识缺口：第一个是基于对潜在 ES 权衡和协同作用的评估，探索将多个 ES 集成到小型 IGS 中的设计和管理知识；第二个是开发 ES 权衡和协同作用的空间评估，这是设想优化 IGS 效益的设计和管理干预措施的关键。