Large Cities Fall Behind in “Neighborhood Biodiversity”

Daniel S Cooper,Eric M Wood,Kat Superfisky,Jo Tarczynski,Anna Novoselov,Lara K Bacasen,Fiona M Osborn,Nurit D Katz

doi:10.3389/fcosc.2021.734931

Abstract

Urbanization is a major driver of global species loss. While cities with suitable habitats and conservation policies may support locally-high biodiversity levels, we suspected that the complexity of managing very large cities might counteract the advantage of large geographic area, and these cities may be less effective at biodiversity conservation. To answer this, we examined the relationship between the number of native indicator wildlife species (mean and maximum) in 112 cities across three metropolitan areas in California (Los Angeles, San Diego, and San Jose), with metrics related to scale and environmental variables. We found that indicator species richness is positively related to area, income (the luxury effect), and pervious cover—including trees, shrubs, and grasses. Despite having a high maximum number of indicator species within their boundaries, the largest cities in our study, Los Angeles, San Jose, and San Diego, do a relatively poor job compared with smaller cities at distributing native biodiversity throughout neighborhoods, as measured by their mean species richness. Such variation in “neighborhood biodiversity” may exacerbate existing inequities in residents' access to nature. Using Los Angeles County as a case study, we compared biodiversity management within the County's 88 cities of various sizes and characteristics. We ranked General Plan wording in terms of references to biodiversity and conservation and created a management metric. We found that municipalities of various sizes that had high management scores generally had high indicator species richness. This suggests that robust policies may be able to overcome the challenges posed by city size and population.

Highlights

Metropolitan areas continue to grow in size (Grimm et al, 2015)
We examined how scale interacts with species richness by characterizing and comparing levels of biodiversity, as measured by wildlife indicator species richness, in individual cities within three separate metropolitan areas in the state of California (Los Angeles, San Diego, and San Jose)
The policies and ordinances we focused on were based on best practices identified by Los Angeles Sanitation and Environment (LASAN), including the Conservation and Open Space Elements of the General Plans, tree ordinances, and landscape ordinances

Summary

INTRODUCTION

Metropolitan areas continue to grow in size (Grimm et al, 2015). Los Angeles County More than 20 cities (of 112 examined) have higher neighborhood biodiversity scores than the largest city (Los Angeles) (Figure 1B) These cities have high levels of indicator species in natural areas such as parks, wildlife preserves, and open space, they have many “dead” grid cells in the largest cities—where no indicator species have been observed, and where few are likely to exist due to low perviousness and near total lack of native habitat (e.g., South LA), resulting in unequal distribution of biodiversity. In addition to examining L.A. County, we reviewed the policies and plans for the largest cities of each of the three counties we studied to determine if there was a difference in management in San Diego that might account for the much higher mean richness as compared to Los Angeles and San Jose (referenced in the Species Richness and Scale section, above). We cannot conclude definitively whether high species richness is a result of conservation plans in place, or a result of ecological context and conditions that existed before plans were conceived

DISCUSSION

Findings

DATA AVAILABILITY STATEMENT