Multiple ecosystem services of informal green spaces: A literature review

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.