Vienna is growing and faces increasing pressure from urban heat, sealed surfaces and competing demands on public space. At the same time, many available spaces in dense neighbourhoods are small, fragmented or residual. The Wiener Wäldchen approach responds to this challenge by using compact, already unsealed green or residual areas for nature-based climate adaptation.

The main objectives are to:

• create small biodiversity islands in the city
• strengthen the network of urban habitats
• improve soil functions, especially rainwater storage
• reduce soil warming and support local cooling
• improve air quality
• bring near-natural green spaces closer to residents
• involve children and young people in planting and learning about urban nature
• show that wilder, more extensive green spaces can complement formal parks

The measure is not designed as a stand-alone solution to urban heat. It is one element in a wider set of climate adaptation and biodiversity measures.

The first Wiener Wäldchen were developed from 2021 onwards. The approach builds on the Miyawaki / Tiny Forest method, adapted to Vienna’s urban conditions and municipal structures.

Implementation usually follows these steps:

•    Suitable sites are identified, with a preference for existing unsealed green or residual spaces.
•    The soil and local conditions are assessed.
•    Soil quality is improved where needed through loosening, soil exchange or natural enrichment.
•    A dense mix of native or regionally suitable tree and shrub seedlings is planted.
•    The planting density is usually around 3 to 4 plants per square metre.
•    A Wiener Wäldchen is usually at least 100 square metres in size.
•    The area is temporarily fenced to protect young plants and support dense early growth.
•    In the first 2 to 3 years, the site is watered when needed, weeds are removed, mulch is used and the fence is checked.
•    After the establishment phase, the mini forest is intended to develop largely on its own, with little ongoing maintenance.

Participation is an important part of the model. Students from nearby primary schools plant trees and shrubs together with municipal staff and local political representatives. This creates local ownership and gives children a direct experience of urban nature.
The project required strong internal coordination at the beginning. Tiny forests did not initially fit neatly into one department’s responsibilities. A shared structure and regular dialogue between municipal departments were therefore essential. Once this framework was established, implementation became more routine.
 

The project is financed by the City of Vienna. The main resources are municipal staff time, site preparation, planting material, fencing, early-stage maintenance and coordination with schools and districts.
A realistic cost range for one Wiener Wäldchen is around EUR 5,000 to EUR 15,000. Costs depend strongly on the site.

Typical cost items include:
•    seedlings
•    soil assessment and preparation
•    soil removal or earthworks, where required
•    planting work
•    mulch and early-stage care
•    watering during the establishment phase
•    temporary fencing

Additional costs can arise if a site needs more complex preparation, irrigation infrastructure or extra equipment such as benches, drinking fountains or bins.
 

Vienna has implemented 14 Wiener Wäldchen so far, with further expansion planned. The existing sites are growing well, and first positive developments in biodiversity are already visible or measurable.

The measure delivers several combined benefits:

• more habitat diversity in small urban spaces
• stronger stepping-stone biotopes within the urban green network
• better soil functions and rainwater retention
• reduced soil warming
• likely positive effects on local microclimates as the mini forests mature
• improved access to near-natural green spaces in dense neighbourhoods
• environmental education for schoolchildren
• greater public visibility for wilder forms of urban nature

The project also has an important cultural effect. It shows that urban green does not always need to be highly manicured to be valuable, attractive and useful.

The main barriers have been institutional and spatial, rather than technical.

Key challenges include:

• identifying suitable sites in dense urban areas
• managing conflicts between different possible uses of public land
• deciding which areas should be transformed and which should remain untouched
• coordinating several municipal departments with different roles and priorities
• creating a shared understanding of what a Wiener Wäldchen is and how it should be managed
• communicating the value of wilder urban nature to the public

The early phase required substantial internal communication. Once roles, expectations and basic procedures became clearer, the approach became easier to repeat.

The Wiener Wäldchen model is highly transferable, especially for cities that want to create small nature-based climate adaptation measures on limited land.

Key lessons include:

• Start with already unsealed sites where possible.
• Build a shared internal structure before scaling.
• Clarify maintenance responsibilities early.
• Involve the municipal departments responsible for environment, parks, forestry and public space from the start.
• Use locally appropriate tree and shrub species.
• Communicate the measure as a biodiversity, soil, education and climate adaptation project, not only as a cooling measure.
• Work with nearby schools to create local ownership and learning opportunities.
• Be clear that the early maintenance phase is important, but that long-term care needs should be low.

The model can be adapted in size, shape and design. Cities can add seating or other equipment, involve different community groups in planting, or place mini forests in parks, squares, housing areas or other public green spaces. The basic principle remains simple: small spaces can deliver large ecological and educational value when they are planted densely, maintained carefully in the first years and then allowed to develop naturally.

• City of Vienna: Wiener Wäldchen
• Smart Climate City Strategy Vienna
• Vienna Forest and Meadow Charter
• Vienna Park Guiding Principles
• Vienna Species and Habitat Conservation Programme "Network Nature"
• Information provided by the City of Vienna Forestry and Agriculture team
• USE / City of Vienna project call notes