Mosses have compared to other plants a large bio-active surface, they transpire more and also actively reduce some pollutants. There is a range of test sites with open air experiments in order to test the effectiveness for fine dust and reduction and air quality improvement. To exemplify the potential a product that makes use of the moss capacities is described for this NBS – type: The City Tree. A City Tree is a bio-tech-filter with the aim to improve the air quality in cities. The City Tree is a compact and mobile construction, vertically planted with different species of mosses on its front and back side. The moss surface contribute to improve the air quality through the binding of air pollutants like particulate matter and nitrogen oxide. Due to its large surface (in comparison to many other plants), mosses store a relatively huge amount of water and at the same time provide a relatively large surface area for water transpiration. As a consequence the transpiration of water leads to a reduction of air temperature on a local scale.

Basic information

Retrofitting + Creation
Measures / Practices


Evapotranspiration 1 1
Shading 1 none
Reflection (Albedo) none
Water Conveyance none
Water Infiltration none
Water Retention none
Water Storage none
Water Reuse none
Water Filtering none
Water Bio-remediation none
Deposition 1
Bio-filtration 1
Habitat Provision none
Connectivity none
Beauty / Appearance 1
Usability / Functionality 1
Social Interaction 1
Role of Nature / Mode of Action: 
- Maximizing the ecological function of natural moss capacity - Mosses have huge surface area  filtering of air pollutants - Transpiration
Technical & Design Parameters: 
City trees are equipped with additional technical solutions: Ventilators inside the vertical construction and underneath the moss surface strengthen the air flow through the installation and thus increase the air filtering and the water transpiration. The ventilators are externally controllable. Furthermore, the city tree is equipped with a technical device that provides real-time information about the city tree as well as the surrounding environment conditions. Depending on the local climate conditions, the city tree has an additional irrigation system. Additional solar panels supply electricity. Otherwise the city tree is connected to the mains.
Conditions for Implementation: 
Flat surfaces for installation is needed, also enough space for loading and unloading.
Benefits & Limitations: 
Benefits: - Air filtering - Mitigation against heat stress - Recreation/relaxing Potential limitations/disservices: - Real performance is still under discussion, further independent studies needed - Transportation and production produce emissions.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme under Grant Agreement No. 730052 Topic: SCC-2-2016-2017: Smart Cities and Communities Nature based solutions