Effects of Green Cities

The study ‚Effects of Green Cities' mirrors the current status of scientific knowledge on urban green structures and regulating effects. Health-related effects such as noise reduction, absorption of particulate matter or indoor or outdoor air quality improvement were not considered. The study serves as an orientation and basis information for implementation projects and potential evaluation and monitoring concepts.

The following research questions (R1-R3) are addressed:

• R1: Which concrete and measurable effects in cities can be traced back to green areas and greening measurements in urban areas?
• R2: Which parameters have been examined and published in recent studies and are suitable to describe the effects of greening measurements?
• R3: Which criteria can be used to describe and evaluate the effects of measurements or already completed projects?

The study builds on an extensive literary analysis of scientific studies and projects on effects of urban greening measurements and published data. For this purpose, a variety of sources was used including scientific publications (with and without peer-review), proceedings, specialist books, dissertations, standards, guidelines, reports and manuals. The data bases ScienceDirect, Google Scholar and Springer Link were used as research base.

Main study findings:

• The scientific description and the estimation of green infrastructure effects in urban areas are only newly established and published in research studies.
• Publications on quantification of effects of green infrastructures have greatly risen in the recent years. Specific emphasis has been put on urban trees, parks, green roofs and vertical greening systems.
• The most important measurable effects are cooling effects and reduced energy consumption. Shading by high crown density, expressed by LAI (Leaf Area Index), and high transpiration rates are the essential functions of green structures.
• The range of recorded parameters and used measurement technology is broad.
• Vague definitions on data and measuring systems as well as strong context dependency lead to difficulties in the comparability of published data and value ranges.
• Initial approaches on prognostic planning tools for the assessment of holistic effects of green structures have been elaborated. Thus, simulation of various greening measurements is feasible.

Clear principles on parameters to be explored, and on the methods to be applied, could be an option to ensure better comparability of results but would strongly restrict the innovative content and potential of research projects. However, independent monitoring studies on established green structures (e.g. urban trees, parks, green roofs, facades etc.) allow for evaluating the effects of implementation projects. Long-term studies and permanent monitoring of selected objects would provide insights into underlying factors and the dynamics of the complex plant and microclimatic interlinkages of green infrastructure in urban environments. Commonly encountered effects, drivers, inhibitors and disruptive factors would be identified.

Univ. Prof. DI Dr. Rosemarie Stangl, DI Dr. Alexandra Medl,
DI Bernhard Scharf, Priv.Doz. Ulrike Pitha
Institut für Ingenieurbiologie und Landschaftsbau
Universität für Bodenkultur, Wien