Urban forests, ecosystem services, green infrastructure and nature-based solutions: Nexus or evolving metaphors?

Approaches and concepts nurturing interdisciplinary knowledge on urban ecosystems have evolved over recent decades and adopted a series of metaphors, including Ecosystem services (ES), Green infrastructure (GI), and Nature-based solutions (NBS). Similarly, research and promotion of urban forests (UF) and their multiple functions have recently grown as a means to address issues affecting urban areas throughout the world. Regardless of the metaphor used, urban forestry has historically provided a common language, science-based practices, and experiences for planning and managing trees and green spaces in cities to provide such benefits. Therefore, we conducted a review of the literature to better understand the origin, trends, and evolution of these metaphors and their institutional and contextual interpretations. Relationships among terms, publication trends and the studies' countries of origin were then used to identify the nexus between urban forestry and these metaphors. We found that ES appears in 2006, GI in 2007 and NBS in 2015. Definitions based on seminal academic publications are now included in national-level policy instruments in several countries and regions. However, in terms of English language publications, the United States leads by a notable margin followed by China, larger European Union countries, Brazil, Australia, and Canada. Similarly, the North-South divide is evident in terms of scientific publication productivity and funding for this type of research. Science and evidence-based guidelines and solutions for integrating and implementing urban forestry practices and experiences are found in several international publications. We suggest that such metaphors, and their socio-political implications, are not as important as the inherent messages. Indeed, changes in both discipline and language are key for communicating the documented importance of urban forestry for enhancing human well-being. A set of criteria that could be adopted to guide the use of these and future metaphors is also presented.