Towards the intentional multifunctionality of urban green infrastructure: a paradox of choice?

The paper addresses why the widely recognized multifunctionality of urban green infrastructure (GI) has not been intentionally incorporated into planning, design, and construction. Within the broader context of nature-based solutions (NbS), GI is expected to deliver multiple ecosystem services (e.g., stormwater attenuation, climate regulation, habitat conservation, and human well-being). Yet, siloed governance, varied terminology across disciplines, and regulation targeting single issues (e.g., water quality, water scarcity, habitat protection) lead to fragmented implementation, missed synergies, and potential disservices. The study’s purpose is to establish shared vocabulary and a practical framework to intentionally consider multifunctionality across 15 GI elements and 15 objectives throughout planning and design, to reveal gaps in the literature, and to propose pathways to better coordination across scales and sectors.

The authors synthesize diverse conceptualizations of GI across regions and disciplines, including terms such as Green Stormwater Infrastructure (GSI), Sustainable Drainage Systems (SuDS), Water Sensitive Urban Design (WSUD), Blue-Green Infrastructure (BGI), and Urban Ecological Infrastructure. They distinguish system-level (landscape) and element-level (site) GI, and, drawing on prior catalogs and reviews, distill more than 40 GI terms into 15 site-scale GI element categories (e.g., green roofs, vertical greening systems, vegetated/non-vegetated infiltration systems, detention/retention, constructed wetlands, urban streams and floodplains, trees/urban forests, urban parks, urban gardens, pervious surfaces, non-infiltrating water storage, bare earth). In parallel, they consolidate numerous functions, services, and disservices discussed in the literature into 15 broad objectives (e.g., stormwater and flood control, stormwater quality, waste management, water provision, heat mitigation, soil remediation, air quality, carbon storage and GHG reduction, biodiversity, human well-being, social justice, noise mitigation, management of raw materials, economic development). The review highlights persistent disciplinary silos: engineered GI is often framed around hydrologic performance, while ecological and planning literatures emphasize biodiversity and human benefits, with underrepresentation of certain objectives (e.g., social justice, noise) and inconsistent terminology that impedes coordinated design.

The study conducted a Web of Science literature query (January 21–22, 2023) across 15 GI elements and 15 objectives, yielding 225 queries (each objective-element pair). Searches spanned All Databases and All Collections and were limited to peer-reviewed articles and review articles. To focus on urban contexts, each query included urban terms in topic fields (e.g., title, abstract, keywords): “urban” OR “built environment” OR “city” OR “cities” OR “metropoli*” OR “megapolis.” Results were aggregated into counts per element-objective pair. Summaries included: (1) summed counts by objective (columns) and by element (rows), acknowledging possible duplication across categories; (2) normalization by element to compute the percentage of an element’s literature that discusses a given objective (visualized via greyscale intensity in the matrix); and (3) normalization by objective to compute the percentage of an objective’s literature that discusses a given element (visualized via circle size). These normalized values form the Element/Objective (E/O) matrix illustrating relative emphases in the literature. The analysis scope excludes coastal restoration and non-GI infrastructure systems (transportation, energy).

• The E/O matrix reveals strong silos. Engineered GI (e.g., non-infiltrating water storage, pervious surfaces, vegetated and non-vegetated infiltration systems, detention basins, ponds/retention systems) is predominantly associated with water-related objectives (stormwater and flood control, stormwater quality, waste management, water provision), with minimal discussion of non-water objectives.
• Conversely, less engineered elements (urban gardens, urban parks, trees/urban forests, bare earth) are discussed primarily in relation to biodiversity and human well-being, and to a lesser extent heat mitigation, with limited integration of water-related objectives.
• Certain element–objective pairs dominate: non-infiltrating water storage dominates water provision; constructed wetlands dominate wastewater/waste management; trees dominate disaster mitigation (excluding flood control). Trees are the most- or second-most discussed element across many non-water objectives.
• Only stormwater management and biodiversity literatures covered all 15 GI elements. Many non-water objectives (e.g., social justice, noise mitigation) are underrepresented across elements. Underrepresented elements include tree pits and non-vegetated infiltration systems for many non-water objectives.
• Green roofs and urban streams/floodplain restoration were among the more balanced elements, with literature spanning both water- and non-water-related objectives.
• The uneven distribution suggests research funding and disciplinary focus drive coverage, creating gaps that hinder intentional multifunctional planning and design.

The findings demonstrate that disciplinary silos impede coordinated, multifunctional GI implementation. Engineered GI literature rarely integrates non-water co-benefits (e.g., heat mitigation, air quality, carbon storage, human well-being), while non-engineered GI discussions often overlook hydrologic functions. To translate multifunctionality into practice, entities responsible for different objectives (e.g., stormwater quality, biodiversity, public health) must coordinate, aligning funding and performance metrics to accommodate multiple objectives. The authors propose a multifunctionality assessment framework, potentially drawing on multicriteria decision analysis, to identify hotspots, trade-offs, synergies, and stakeholder preferences relevant to specific projects. They advocate systems thinking across scales (site to landscape), adaptive/flexible design to accommodate evolving objectives, and performance-based design with ongoing monitoring and evaluation. Addressing climate change extremes (intense rainfall, drought, heat) necessitates resilient GI designs, further reinforcing the need for integrated, cross-sectoral planning. Without structured decision support and policy alignment, the proliferation of options can create a paradox of choice that undermines timely and equitable implementation.

This study consolidates 15 GI elements and 15 objectives into a practical E/O matrix that reveals persistent silos and highlights opportunities for coordination across planning, design, and construction. It offers a shared vocabulary and a structured lens to intentionally consider multifunctionality, guiding both researchers and practitioners. In the short term, applying adaptive/flexible and performance-based design principles, along with monitoring and evaluation, can progress implementation while accommodating future expansion of objectives. Long term, the authors call for formal multifunctionality assessments, inter- and transdisciplinary collaboration, supportive policies, and political will to operationalize systems thinking and realize multifunctional GI at scale. Future research should develop tools to determine optimal objective sets per site in relation to the surrounding GI system, and track how interdisciplinary funding and practice reduce silos over time.

• Literature-sourced biases: The E/O matrix reflects academic publications and funding priorities; it may not represent municipal practices or on-the-ground priorities. Some objectives and elements are underrepresented due to research funding trends rather than true irrelevance.
• Counting and normalization caveats: Publications can be counted in multiple categories, so summed totals are not unique counts; results indicate relative emphasis, not absolute coverage.
• Scope constraints: Focus is limited to urban contexts, excludes coastal restoration and non-GI infrastructure (transportation, energy). Some GI-related benefits (e.g., social justice, noise mitigation) are conceptually important but insufficiently quantified.
• Generalizability and valuation: Many objectives lack standardized metrics, complicating cost-benefit analyses and pre-implementation trade-off assessments. Maintenance costs and climate change uncertainties further limit generalizability across contexts.
• Temporal snapshot: Queries were conducted in January 2023; subsequent literature may shift emphases.