*5.5. Disciplinary Orientation*

The findings of this review category—showing that the vast majority of urban greenway research falls into the domain of social science and interdisciplinary research or planning—dovetail largely with the former review category on research themes. Studies addressing social outcomes, for example, include links between urban greenways and user perceptions [67,68], aesthetic response [69], public access [70,71], physical activity levels [46,72], crime [73], and racial commingling [74].

As noted above, the strong social science orientation of urban greenway scholarship is noteworthy in its differentiation from greenways writ large, which has a strong foundation in environmental science and landscape ecology. Yet, the relatively minor emphasis on natural science should not be interpreted as a lack of attention to environmental concerns. Over 40% of studies in the literature under review adopted an interdisciplinary and/or planning orientation, and this is, in many cases, synonymous with a socio-ecological approach. In urban settings that are built by and for people [28], this is appropriate. Indeed, cities are, in many ways, a classic socio-ecological system where bio-geo-physical elements and processes interact with people and institutions [75,76]. Thus, the results of this review can be seen as heartening evidence that scholarship is responding to the practical realities in which urban greenways are embedded.

The lack of humanities-based scholarship on urban greenways is a noteworthy gap. Humanities scholarship draws upon environmental history and political ecology and often adopts a reflexive position that shines a critical light on the topic at hand. Reflecting upon related research in urban forestry and urban greening, Bentsen et al. [35] suggest that a lack of humanities scholarship can reproduce a meta-narrative that only emphasizes benefits and goods. The same may be true for urban greenways research. For relevant examples of humanities scholarship pertaining to urban greenways that were not captured in this review, see Chung et al. [77] and Safransky et al. [78].

## *5.6. Extent*

Reflecting the heterogeneous character of urbanized landscapes, studies in this review category were broadly distributed across urban centers (34.6%), multi-scalar networks (25.0%), and metropolitan areas (21.2%). This suggests that urban greenways scholarship is addressing a range of scales across urbanized areas and it is encouraging to see many studies addressing multiscalar networks that cut across urban and metropolitan extents. For example, Angold et al. [79] found that small mammals may depend on urban greenways extending from the urban center in Birmingham, UK to adjacent boroughs for dispersal. Cook [80] found that an ecological network plan provides modest but important improvement in ecological systems in the Phoenix urban area. Other multi-scalar studies found that trail use can differ by trail segment [81] and by surrounding land use [82]. Of particular relevance to the topic at hand, the latter study found that greenways surrounded by dense residential and mixed land uses, advanced street networks, and large parks were especially important for increasing physical

activity. Reflecting Ahern [1], these examples suggest that *networks* of greenways cutting across scales and land uses are important for generating a range of socio-ecological benefits.

## *5.7. Landscape Setting*

Many urban greenways are embedded in a range of landscape settings, as revealed through our assessment, which found that well over half (60%) of reviewed studies crossed multiple settings. Another way of interpreting this finding is that urban greenways are doing exactly what they are conceived to do, namely, provide ribbons of green space in landscapes that might otherwise lack green space at all. This is especially true in the complex, heterogeneous fabric of urban areas, where land contestation can make green space provision all the more difficult.

The next most common setting is waterfronts. This is not surprising, as riparian corridors are routinely identified as one of—if not the—most common settings for greenways [1,4,19]. Studies on waterfront greenways address a range of topics, including but not limited to, stream rehabilitation and public access [83], dispersal corridors for invasive trees [84], and links between human perception, safety, and use [85]. One study found that waterfront greenways close to residential zones, employment centers, and key public services such as hospitals and schools increase use [71]. Focusing on the urban-rural fringe, McGuckin and Brown [46] found that stormwater management facilities can be integrated into existing greenways, and if protected during development, can generate a range of socio-ecological benefits.

Reflecting an ongoing movement to reconceive outdated urban landscapes, a handful of studies address one of the boldest and most dramatic "freeways-to-greenways" to date. In Seoul, Korea, the Cheonggyecheon freeway was torn down and replaced by an urban stream and linear park in 2003–2004, making this project both a good example of adaptive reuse and waterfront greenway. Research shows that land value premiums for parcels within the 500 m walkshed of urban greenway entrance points were notably higher than former freeway on-ramps [62]. Related studies also found that employment density increased within a 1.2 km zone surrounding the new urban greenway [33], and that land conversion from single-family residential to commercial was more likely to occur within 1.5 km of greenway pedestrian entrances.

It is worth noting that freeway-to-greenway projects—including early precedents in Portland, Oregon and San Francisco, California—are harbingers of similar projects being explored in other cities [62]. These are complex feats of civil engineering layered with substantial political and economic mobilization. The transformative effect of such projects may foretell increased scholarship on the complex planning, design, and management of such multi-layered landscapes, as well as interconnected effects related to land use change, property value, public access, and equity.
