Walls offer potential to improve urban biodiversity

Chundi Chen,Yuncai Wang,Jian Cui,Longfei Mao,Yonggui Qiu

doi:10.1038/s41598-020-66527-3

Abstract

Within urban environment with high-rise buildings and structures, walls represent the most common vertical spaces. Conventionally, such spaces are viewed as abiotic areas, where spontaneous flora is neglected. Through investigations in a typical mountainous city Chongqing, this study concerns the spontaneous species diversity on walls and the influences of wall factors and the adjacent environment. A total of 239 vascular plant species belonging to 172 genera and 75 families were found; 90% of the species are indigenous. More fern species inhabit walls, compared with xerophytes that dominate general urban environment. Variation partitioning indicated that wall attributes played a more important role in explaining the total variation in wall vegetation composition and structure than did the adjacent environment. Given that there are limited possibilities to extend more green space in urban land environment, we support a “let Nature take its course” approach to improve urban biodiversity, where vertical urban space with spontaneous flora can act as a valuable complement to biodiversity and ecosystem services in dense urban environment. This study should raise urban designers’ and ecosystem managers’ awareness of the possibilities of this type of informal, unconventional habitat as a “supplement” for urban greening and landscaping.

Highlights

Within urban environment with high-rise buildings and structures, walls represent the most common vertical spaces
A total of 239 vascular plant species belonging to 172 genera and 75 families were found across the 413 quadrats
Walls with comparatively harsher conditions, supported 239 vascular plant species belonging to 172 genera and 75 families

Summary

Introduction

Within urban environment with high-rise buildings and structures, walls represent the most common vertical spaces. We have long neglected the fact that a city is a three-dimensional space that has a large quantity and variety of walls They may offer great spatial potential for colonisation by naturally dispersed vegetation, especially for highly dense cities with notably limited land resources. Different from two-dimensional land environment with deeper soil and good hydrological conditions, the species composition and structure seems to depend more on extrinsic conditions, such as the surrounding environment, and intrinsic attributes, such as the wall material[7] These silently growing species are often neglected, they can contribute important ecosystem services in the context of the combined impact of urbanisation and climate change[6]. European chasmophytes Brassica cretica subsp. cretica, Centaurea raphanina subsp. mixta, Erysimum corinthium and Silene spinescens found on the walls of a castle were found commonly on adjacent rocky slopes[18]

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