Synergies or Trade-Offs? Optimizing a Virtual Urban Region to Foster Plant Species Richness, Climate Regulation, and Compactness Under Varying Landscape Composition

Nina Schwarz,Sonja Knapp,Falk Hoffmann,Michael Strauch

doi:10.3389/fenvs.2020.00016

Abstract

Ongoing urbanization forces us to reflect on how we can cater for multiple targets when building cities. In this study, we investigate whether compactness as a common urban development strategy, climate regulation as an example for an ecosystem service, and vascular plant species richness as a measure of biodiversity form a synergistic relationship or whether trade-offs exist. We use a genetic algorithm to optimize the spatial allocation of three types of land cover blocks in a stylized urban region. These blocks are categorized as high-density, low-density, or park blocks, depending on the proportion of green and built-up cells within each block. We systematically vary landscape composition at the block level, but keep city size constant. Our most important finding is that the relationships of target functions can shift between trade-off and synergy, and this is shaped by landscape composition. For example, we found a trade-off between species richness and urban compactness in landscapes with large proportions of high-density areas and parks, while they have a synergistic relationship in low-density landscapes. Such dependencies of trade-offs and synergies on landscape composition need to be explored further, which may help address the wickedness of urban planning problems.

Highlights

More than half of the world’s population is living in cities and the share of urban population is rising further (United Nations Department of Economic and Social Affairs Population Division [UN DESA], 2018)
We investigate whether urban compactness, ecosystem services and biodiversity form a synergistic relationship or whether trade-offs exist
We first explore one example simulation, before analyzing whether we find trade-offs or synergies between the target functions Afterward, we investigate the relations between landscape configuration and the targets

Summary

Introduction

At least three arguments impede straightforward solutions: First, a variety of ecosystem services (i.e., the benefits humans derive from ecosystems, such as carbon sequestration or water provision, Millennium Ecosystem Assessment, 2005) needs to be considered. In the literature, both direct and indirect relationships between ecosystem services have been documented (Bennett et al, 2009): Direct relationships result from interactions between the services, while indirect relationships are due to the same driver affecting both services. Other ecosystem services might rather benefit from compact green spaces Such opposite responses indicate trade-offs between ecosystem services, while similar responses indicate synergies (Cord et al, 2017)

Methods

Results

Conclusion