Ecological functions and services in the context of a multidimensional assessment for urban green spaces

• Ökologische Funktionen und Leistungen im Kontext einer multidimensionalen Bewertung urbaner Grünflächen

Daniels, Benjamin; Schäffer, Andreas (Thesis advisor); Roß-Nickoll, Martina (Thesis advisor)

Aachen (2020)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2020

Abstract

Facing the growing amount of people living in cities and, at the same time, the need for a compact and sustainable urban development to mitigate urban sprawl, it becomes increasingly important that green spaces in compact cities are designed to meet the various needs within an urban environment. Urban green spaces and its benefits can address many of the growing key challenges in cities: temperature regulation, air purification, noise reduction and cultural benefits like recreation and contact to nature contributes to human well-being and health. Moreover, urban green spaces can serve as core areas of species habitats which is a basic requirement to conserve or promote biodiversity and to preserve ecological processes in urban ecosystems. We therefore aimed to develop a novel approach to evaluate urban green spaces: a methodology in which urban green spaces are assessed quantitatively from the perspective of different disciplines with regard to their provided ecosystem services and functions. This integrative, multidimensional approach was established by deriving ecological, microclimatic and socio-cultural indicator values and proposing a new, holistic metric. To adapt this multidimensional assessment approach, a consistent and comprehensive classification system to characterize the structural composition of urban green spaces was developed. Single structural green space elements were defined and ecologically characterized with regard to conducted vegetation surveys and recorded structural parameters. The classification system and the assessment approach to evaluate the supply of ecosystem services were applied to nine different urban green spaces in the city of Aachen, Germany. The contribution of single park structures to the provision of specific ecosystem services at a site could thus be quantified. On the other hand, potentials to improve the supplies of ecological functions and services for different park types were unmasked. Plant-pollinator interactions and the corresponding service of pollination, as a particularly relevant ecological function of green spaces within cities, were empirically investigated in structural green space elements: Specific patterns of recorded insect communities among the different structural elements and park types were identified. It was shown that the structural composition of green spaces and the corresponding design and maintenance significantly affects the abundance and diversity of flower-visiting insects. Near-natural management concepts for urban green spaces can improve the diversity of pollinating insects and, consequently, of pollination interactions between plant species and insects. Results clearly indicates the strong potential of cities to provide a habitat for different groups of pollinators. In order to access this refuge, it is necessary to rely on near-natural concepts in design and maintenance, to create a wide range of flower diversity and to use even small green patches. Based on the findings, we encourage for an integrated management of urban free spaces to consider parks as key habitats for pollinators in urban environments. The empirical data for pollination in structural green space elements were integrated into a Bayesian belief network in order to update the indicator values for pollination of the multidimensional assessment approach. The application has revealed promising characteristics of this statistical method in order to integrate empirical data into an assessment and decision process for the planning of urban green spaces. It will facilitate the management and communication activities for urban planners. The generated approach of a multidimensional assessment for urban sites was subsequently transferred to the field of renewable energy production in agricultural landscapes. By this, we tested the established socio-ecological strategy within another context: The study argues the importance of a thorough ecological basis for social acceptance analyses and exemplifies an integrated approach in which energy scenarios are evaluated from both ecological and social perspectives. The case study highlights the importance of integrated methods to gain sustainable processes in anthropogenic landscapes, their corresponding societies and ecosystems. This doctoral thesis has an ecological identity that is proactively integrated into a transformative science approach: We conducted an analysis of ecological patterns and processes, especially with regard to the function of pollination in cities, and derived specific ecological indicator values. Nevertheless, a particular attention within this thesis was also paid on the integration of these ecological findings into a comprehensive, multidimensional framework. For this reason, major effort was made to the appropriate classification in a more aggregated context. In this way, the research is capable of practical implementation into administrative planning and management procedure.