Can patterns of urban biodiversity be predicted using simple measures of green infrastructure?

Jonathan P Sadler,Adam J Bates,Ane Kirstine Brunbjerg,Emma J Rosenfeld,Robert E Fowler,James D Hale

doi:10.1016/j.ufug.2018.03.015

Abstract

Urban species and habitats provide important ecosystem services such as summertime cooling, recreation, and pollination at a variety of scales. Many studies have assessed how biodiversity responds to urbanization, but little work has been done to try and create recommendations that can be easily applied to urban planning, design and management practice. Urban planning often operates at broad spatial scales, typically using relatively simplistic targets for land-cover mix to influence biodiversity and ecosystem service provision. Would more complicated, but still easily created, prescriptions for urban vegetation be beneficial? Here we assess the importance of vegetation measures (percentage vegetation cover, tree canopy cover and variation in canopy height) across four taxonomic groups (bats, bees, hoverflies and birds) at multiple spatial scales (100, 250, 500, 1000 m) within a major urban area (Birmingham, the United Kingdom). We found that small-scale (100–250-m radius) measures of vegetation were important predictors for hoverflies and bees, and that bats were sensitive to vegetation at a medium spatial-scale (250–500 m). In contrast, birds responded to vegetation characteristics at both small (100 m) and large (1000 m) scales. Vegetation cover, tree cover and variation in canopy height were expected to decrease with built surface cover; however, only vegetation cover showed this expected trend. The results indicate the importance of relatively small patches of vegetationfor supporting urban biodiversity, and show that relatively simple measures of vegetation characteristics can be useful predictors of species richness (or activity density, in the case of bats). They also highlight the danger of relying upon percentage built surface cover as an indicator of urban biodiversity potential.

Highlights

To describe patterns in urban biodiversity and understand their causes, researchers have employed varying measures of urban context (Sadler et al, 2010)
We address the following research questions: 1) How much of the variation in species richness of birds (Aves), bees (Apoidea), hoverflies (Syrphidae) and activity density in bats (Chiroptera) is linked to measures of vegetation cover, tree cover and diversity of tree canopy height? 2) At which spatial scales does each taxon most strongly respond to these vegetation measures? 3) What is the nature of the relationships between vegetation and species richness/activity density? 4) To what extent does the proportion of built surface correlate with these vegetation metrics, and do these patterns vary with spatial scale?
Bird species richness increased with greater variation in tree canopy height (STD) at a large spatial extent (1000 m) and increased with tree cover at small scale (100 m) with very limited effects of vegetation cover and median canopy height at all scales (Fig. 2b, Table 1)

Summary

Introduction

To describe patterns in urban biodiversity and understand their causes, researchers have employed varying measures of urban context (Sadler et al, 2010). Population density and distance to the urban center have facilitated coarse comparisons between studies; these measures do not always translate into urban management practice (McDonnell and Hahs, 2013). Other measures, such as built surface cover, are potentially more useful for translating into urban planning practice. Stereophotogrammetry using aerial photography is an alternative source of data on canopy height, is simpler to collect than LiDAR, and is often cheaper and spatially more extensive These techniques produce standardized high-resolution information on the structural complexity of vegetation over large spatial extents much more than traditional ground-based vegetation survey approaches

Methods

Results

Conclusion