Hamburg’s Climate Plan
The city of Hamburg launched its first climate adaptation action plan in 2013, followed by the Climate Plan (2015) and Climate Adaptation Transformation Path (2019).
The 2020 Climate Protection Law mandates sector-specific measures to achieve climate neutrality by 2045. In 2025, Hamburg adopted a comprehensive climate adaptation strategy involving multiple sectors and local stakeholders to prepare for ongoing climate impact.
A tree registry for better planning and green space management
Why trees matter
Early on, the city recognised that trees are an essential part of the green infrastructure and key to the urban climate. With approximately 250,000 street trees, 600,000 park trees, Hamburg boasts a very large tree population. This is one of the reasons why Hamburg is perceived as a "green and liveable metropolis." However, summer heat waves, droughts, and storms pose a threat to the tree population. Furthermore, newly introduced diseases and pests, favoured by higher temperatures or altered precipitation patterns in Northern Germany, are increasingly endangering more tree species.
Assessing trees' response to climate change
The project “Urban Trees in Climate Change” (SiK) assessed and monitored the sensitivity of trees to climate stress and developed supporting measures to preserve and enhance the urban tree population in the face of climate change. Results from a Hamburg research initiative highlight that especially old trees are our climate specialists. Studies show that these trees, with their extensive root systems, are able to access water reserves and ensure sufficient transpiration even during periods of soil water shortage.
The SiK project develops an integrated concept for adapting Hamburg's tree population to climate change. This concept includes climate impact monitoring for street trees to assess the vulnerability of tree species to drought and heat stress. Subsequently, measures and tools will be developed to maintain and further develop the tree population in times of climate change.
Making the information available to all
The Hamburg Tree Register has been available online as a public tool since 2019. It documents and maps over 230,000 street trees in Hamburg, detailing information on tree species, age, size, and location. Users can search, filter, and export maps. The register is updated annually and targets both residents and professionals, providing transparent information about the urban tree population. It is freely accessible via the City of Hamburg’s website.
The tree registry provides legally valid documentation and supports targeted maintenance, optimising resource allocation for tree care. For each individual street tree, the register contains digital data on location, species, year of planting, crown diameter, and trunk circumference. Data on the condition of the trees is also recorded. During the annual inspections by the horticultural departments of the seven districts, the trees are checked for traffic safety, diseases, and pests.
In 2025, Hamburg won the "European City of Trees" (ECOT) award for its approach to climate change adaptation through tree management.
Citizen engagement
Since 2011, the " My Tree – My City " planting campaign has enabled Hamburg residents to participate in planting street trees through donations. The main objective is to strengthen the connection between residents and urban greenery, especially street trees, and to communicate the value that trees provide to the city.
Lesson learnt and next steps
Hamburg’s experience shows that urban tree resilience is not accidental: it depends on adequate space, long-term planning, targeted care, and species that can cope with urban stress. Above all, the city has learned that mature trees are irreplaceable climate assets. Their large crowns and deep root systems deliver cooling effects that cannot be compensated by new plantings in the short or medium term. Protecting existing trees is therefore a cornerstone of effective climate adaptation.
Strong political backing, alignment with Hamburg’s broader climate strategies, and close cooperation between IT providers, municipal departments, and research institutions have been critical to success. This collaboration enabled the development of a legally robust, digital tree registry that supports transparent decision-making and more efficient allocation of maintenance resources.
Looking ahead, Hamburg is prioritising the preservation and improvement of existing tree sites. Tree removals are minimised wherever possible, and when unavoidable, replacement plantings are carried out as close to the original location as possible. At the same time, planting sites are being upgraded to ensure long-term tree survival, with sufficient root space, permeable tree pits, and appropriate protection measures.
For new plantings, the focus is firmly on future-proof design. Young trees are watered according to need, soil moisture monitoring is being expanded, and suitable replanting sites are continuously identified—especially in compact urban areas—to create a more continuous and resilient tree network. Species diversity is being increased, with a stronger emphasis on mixed avenues and previously underrepresented, site-appropriate species from the GALK list.
The next phase of Hamburg’s approach brings tree management further into the digital age. The city plans to enhance monitoring systems, build more comprehensive tree data, and pilot digital twins for 2,000 trees in the Bergedorf district to assess ecosystem performance. If successful, this system could be expanded to other parts of the city. In parallel, tree data will be linked with irrigation sensors and city-wide green space management tools, cross-referenced with geographic data on heat exposure, rainfall patterns, and soil sealing risks—turning the tree registry into a central instrument for climate-resilient urban planning.
Hamburg, Germany
Covenant Signatory since 2008
Population: 1,964,021
Area covered: Local (755.09 km2)
Key figures
- 3.200 Hectares of green spaces
- 250,000 street trees & 600,000 park trees
GHG emissions ambitions:
- -55 % GHG emissions reductions by 2030
- -95% GHG emissions reductions by 2050
Useful links
- https://www.hamburg.com/visitors/getting-around/moinzukunft-22640
- https://www.hamburg.de/politik-und-verwaltung/behoerden/bukea/themen/klima/klimaschutz-klimaplan/klimaanpassungsstrategie-1026122
- https://www.moinzukunft.hamburg/hamburger-projekte-zum-klimaschutz/hamburger-stadtnatur-schuetzen/forschungprojekt-stadtbaeume-im-klimawandel-785400