1 In search of time-honored examples of nature-based solutions

Since its conceptions by the International Union for Conservation of Nature (IUCN) in 2012 (IUCN 2012, pp.24–25) and by the European Commission (EC) in 2015 (EC 2015, p.24), nature-based solutions (NBS or NbS) have been gaining steady traction in both professional and academic circles, primarily in the European countries (Kotsila et al. 2021, p.252; Nesshöver et al. 2017, p.1216; O’Sullivan et al. 2020, p.2; Pauleit et al. 2017, pp.31–32). For a most recent example, at the 11th International Conference on Innovation in Urban and Regional Planning (INPUT2020), held September 8–12, 2021, at the University of Catania, Italy, “Integrating NBS into urban and regional planning processes and science” was the overarching theme for discussions [see La Rosa and Privitera (2021)]. A latest Google Scholar search, as another example, resulted in 17,100 English publications since 2016 with “nature-based solutions” in their titles, out of which 7150 were published in the first eight months of this year.Footnote 1

Nature-based solutions are human actions and social processes through which people from all walks of life work together to build and/or renovate nature-inspired, ecosystem-based green infrastructures (GIs) that help address the environmental, social, and economic challenges they face and meet their needs for survival, development, and flourishing (EC 2021c; IUCN 2021).Footnote 2 Among all NBS enthusiasms in the past decade, the most prominent is indisputably a batch of high-profile NBS demonstration projects in selected cities and regions, primarily in Europe (EC 2015, 2016, 2020, 2021a, b). These projects are funded by the European Commission through the “nature-based solutions and re-naturing cities” initiative in its Horizon 2020 program (EC 2015, pp.5–6; EC 2016; EC 2021a, b), aiming inter alia “to provide best-practice examples that can be replicated globally.” [Cohen-Shacham et al. 2019, p.20; EC 2016, p.29, p.31, p.35; O’Sullivan et al. 2020, p.1 (the quote)]Footnote 3 These anticipated best NBS practice examples, according to the European Commission (2015, p.24; 2016, p.28), would showcase effective NBS projects that possess a set of “key features” (EC 2016, p.28; see Table 1).Footnote 4

Table 1 Key features of an effective NBS project. [adapted from EC (2016 , p.28)]

Why is it necessary to create such examples through funded projects? The 2016 EC report explains, “Robust EU-wide evidence of the cost-effectiveness and longer-term social, economic, cultural and ecological benefits of these solutions [NBS and their GI products, that is—see footnote 2 of this essay] is currently lacking and this has prevented their wider deployment.” (EC 2016, p.28) Still, it is noteworthy that only a year earlier in 2015 did the European Commission showcase a set of practical projects from around the world, including several from the EU countries, as “examples of nature-based solutions” (EC 2015, pp.52–66). Why did these EU examples not make the Commission’s “EU-wide evidence” list? The projects in these examples and their GI products might not be “robust” enough, one may speculate solely based on their recency—they were either still ongoing or newly completed at the time of 2016 reporting and had yet to stand the test of both time and practice (see key feature 5 in Table 1).

2 Effective NBS projects and long-standing GIs they yielded

While the above statement about the lack of “robust EU-wide evidence” is still subject to further vindication, there is already a myriad of robust evidence worldwide. These are effective NBS projects and long-standing GI products they led to throughout the world that possess, or even go above and beyond, those key features the European Commission identified in its 2016 report (see Table 1). In fact, building nature-inspired GIs belongs to a broad class of fundamental and arguably primordial social practice Homo sapiens has been involuntarily engaging in throughout thousands of years of co-evolution with nature. This social practice is codified lately as socio-ecological practice (La Rosa 2019; Liao 2019; Steiner 2020; Xiang 2019a).

Socio-ecological practice is an umbrella term referring to “the human action and social process that take place in specific socio-ecological context to bring about a secure, harmonious, and sustainable socio-ecological condition serving human beings’ need for survival, development, and flourishing. Socio-ecological practice includes six distinct yet intertwining classes of human action and social process—planning, design, construction, restoration, conservation, and management.” (Xiang 2019a, p.7).

Throughout the history of socio-ecological practice, human beings have created a great wealth of effective projects of building nature-inspired GIs whose products provide lasting benefits and stand the test of time. By the European Commission’s standards (Table 1), these projects today would be qualified for and could therefore be termed, effective NBS projects. Some of them have been documented and archived, but many of them have not. Among those documented are the projects leading to the Dujiangyan (都江堰) irrigation system in Sichuan, China (256 BC—present) (Needham et al. 1971, p.288; Xiang 2014, pp.65–66); the Fushougou (福寿沟) stormwater management system in Ganzhou (赣州), China (1069—present) (Han 2012); the Red Flag Canal in Henan, China (1969—present) (Chen and Xiang 2020a, b; Li et al. 2021; Xiang 2020a); the Woodlands New Community in Texas, USA (1974—present) (Forman 2002, pp.102–104; Lyle 1999, p.103, p.237; McHarg 1996, pp.256–264; Xiang 2016, pp.56–57; Xiang 2019b, pp.166–167; Yang 2019; Yang and Li 2016; Yang and Li 2019, pp.217–219); afforested woodlands in the Alps that provide multiple ecosystem services (Knott 1991; Mayer and Ott 1991); Škocjanski Zatok Nature Reserve in Koper, Slovenia, that helps mitigate local impacts of sea level rise (Ivajnšič and Kaligarič, 2014; Jurinčič et al. 2011); ancient woodlands and urban parks in many European cities, such as Eilenriede in the heart of Hanover, Germany (Landeshauptstadt Hannover 2016; Oppermann and Thies 2017).

3 Problem-solving projects versus demonstration projects

These effective NBS projects are all problem-solving projects with three distinctive characteristics that distinguish them from those EC funded demonstration projects.

First, as problem-solving projects, they are impelled directly by the local needs, not driven by external grants. As such, their ultimate standard of success is whether the problems they are entitled to address are resolved completely or mitigated to the satisfaction of the local people; not if the policy ideas, scientific principles, or proposed management guidelines they are commissioned to demonstrate are efficacious—have the power to produce anticipated effects.Footnote 5

Second, as problem-solving projects, they have no stopping rule and entail recurring operations. Because the real-world problems they aim to address within specific socio-ecological contexts are wicked by nature (Xiang 2019a, p.8),Footnote 6 it is less if ever possible to have a clearly defined and/or collectively agreed set of criteria for measuring and determining project success or even progress; furthermore, implemented solutions often if not always create new, unexpected problems that require additional efforts and continuous reworking. By contrast, the demonstration projects can and almost always have to follow “procrustean strategies” (Schön 1987/2001, p. 192) to avoid the wicked parts of real-world problems (Xiang 2021a, p.83); they thus have clear-cut criteria jointly set by the granters and grantees for measuring and determining success in efficacy demonstration (Churchman 1967, B-141). With well-defined stopping rule, demonstration projects are one-shot deals.

Third, as problem-solving projects, they operate through a trial-and-error process, instead of a planned project lifecycle. The socio-ecological practice of building nature-inspired GIs in these projects is by and large what the British sociologist Stephen Ball and the Lebanese-American essayist Nassim Taleb described a trial-and-error process of bricolage and tinkering. In this process, practitioners—the project doers—proceed with “the zest for bricolage” and “hunger for trial and error” (Taleb 2012, p.226), barely following general principles or step-by-step guidelines even when they are readily available (Davoudi 2006, p.22). Using “fast and frugal heuristics” in “an adaptive toolbox” (Gigerenzer 2008; Gigerenzer & Brighton 2009, p.120, p.134), they borrow and copy bits and pieces of ideas from elsewhere, draw upon and amend locally tried and tested approaches, cannibalize known theories, techniques, and technologies (Ball 1998, p.126).Footnote 7 By contrast, commonplace in the demonstration projects is a systematic process, championed by many academic researchers (e.g., Albert et al. 2021; Cohen-Shacham et al. 2019; Woodruff & BenDor 2016, among many others), of recontextualizing and implementing general principles or policy/management guidelines (e.g., EC 2021b).

4 Time-honored examples of nature-based solutions

Because of these distinctive characteristics, these effective NBS projects along with their long-standing GI products set a type of NBS examples that on the one hand, meets, or even goes above and beyond, the EC standards (Table 1); but on the other hand, is different from the best NBS practice examples the EC funded projects aim to produce (EC examples henceforth for brevity). They are time-honored NBS examples (henceforth) of real-world problem-solving created inadvertently by generations of practitioners through a trial-and-error process of bricolage and tinkering. Here, the adjective time-honored means literally being “honored because of age or long usage” (Merriam-Webster 2021b).

Specifically,

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    These time-honored NBS examples are concrete instances of effective real-world problem-solving, which may or may not be imitated but certainly cannot be “replicated globally” as has been anticipated for the EC examples [O’Sullivan et al. 2020, p.1 (the quote)];

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    Their exemplary status is a recognition rather than an anticipation—an unexpected byproduct of problem-solving activities performed only to the satisfaction of local and/or regional communities, not an anticipated deliverable to meet a priori standards of success set by the granters and grantees of demonstration projects. As such, these time-honored NBS examples, however imperfect they may be, serve as more realistic and compelling inspirations for practitioners and the general public;

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    They are results of continuous acts of bricolage and tinkering performed by generations of practitioners and/or scholar practitioners with use-inspired approaches to research, not products of one-shot demonstration projects done by academic researchers and/or knowledge brokers with curiosity-inspired approaches. Therefore, these time-honored NBS examples and the underlying approaches resonate more closely with the ways real-world practitioners do their jobs.Footnote 8

With these characteristics, the time-honored NBS examples constitute a unique fountainhead of inspiration and ecophronesis [i.e., ecological practical wisdom; see Austin (2018); Xiang (2016)] and a valuable source of instructive lessons that complement the examples the EC funded demonstration projects aim to create.

5 Digging up time-honored examples of nature-based solutions

Unfortunately, a great many time-honored NBS examples throughout the human history remain the best kept secrets and mostly undocumented. Examples that are documented, on the other hand, like those listed in Sect. 2 of this essay, are usually known only by people in a small geography or among scholars of a particular field (e.g., cultural anthropology; regional geography; history of science and technology; histories of architecture, landscape architecture, urban and regional planning; sinology; traditional ecological knowledge; ecological wisdom).Footnote 9 Consequently, time-honored NBS examples as a whole are not in the public knowledge domain. As a historical heritage with intrinsic values, they are much underappreciated; as buried resources of inspiration and ecophronesis, they await our exploitation to benefit the contemporary socio-ecological practice

As such, we hereby advocate with great enthusiasm the unearthing and documenting of time-honored NBS examples. We invite practitioner and scholar colleagues from around the world

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    To actively dig into histories of socio-ecological practice for time-honored NBS examples, systematically document the human actions and social processes these examples entail, critically examine both the acts of bricolage and tinkering practitioners took and the concomitant consequences, closely investigate the ways practitioners coped with the wicked parts of real-world problems, and showcase the long-standing GI products as tangible manifestations of human NBS endeavors;

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    To explore and/or illustrate ways through which these time-honored NBS examples, once unearthed and documented, can be made more useful—relevant, actionable, and efficacious (Xiang 2019c, p.1)—to the contemporary socio-ecological practitioners and socio-ecological scholar-practitioners in NBS practice and research. This task necessarily requires the prudent use of a holistic socio-ecological approach, as advocated by many authors (e.g., Bayulken et al. 2021; Curran and Hamilton 2020; Janzen and Fischborn 2016; Kotsila et al. 2021; La Rosa and Pappalardo 2020; Shi 2020), through which societal issues pertaining to equity and justice are taken into due consideration in NBS practice and research;

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    To showcase concrete instances in which a time-honored NBS example was made useful to, and actually used by, real-world practitioners in their socio-ecological practice of building nature-inspired GIs;

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    To develop articles that present these findings precisely "in small words" (Xiang 2020b) and share through Socio-Ecological Practice Research (SEPR), the home journal of Ecopracticology—the study of socio-ecological practice (Xiang 2019a, p.12), so that they are permanently archived in what we hope to build the international depository of time-honored NBS examples.

“There is nothing as inspirational as a good example.” (Xiang 2020b, p.126) In the very spirit underlying this aphorism, we admire EC’s ambition to create effective NBS examples and applaud the endeavor toward this end through the demonstration projects; at the same time, as outlined above, we take on an equally important and challenging task and cordially invite practitioners and scholar-practitioners from all pertinent professional and academic fields to join us in this worthy adventure.