Urban areas play a central role in both climate mitigation and adaptation: they concentrate population and infrastructure, making them highly exposed to climate impacts, while their high greenhouse gas emissions also make them significant contributors to climate change.

According to several indices, Vietnam is among the countries most affected by extreme weather events and remains vulnerable to climate change impacts, particularly in low-lying and coastal regions such as Central Vietnam. The city's historic centre was built on the former floodplain of the Huong River, with parts of the city lying only 1.8 to 3.5 metres above sea level, with areas below two metres flooding regularly. The surrounding region of Thua Thien Huế is considered the most flood prone province in Vietnam, while at the same time suffering from heatwaves and storms. Climate models project further temperature increases (up to roughly 1.1 to 3.3 degrees Celsius by 2070, depending on the scenario) and rising total rainfall.

Given these pressures, the GreenCityLabHuế works to determine the potential of nature based solutions for climate adaptation, climate mitigation and additional ecosystem services in Huế, and to develop concrete and feasible urban development solutions together with local stakeholders.

The project combined analytical, participatory and demonstrative components:

In 2020 a status quo assessment was performed, where land-use data was analysed to map the existing distribution of green and blue infrastructure across Huế, covering forest, farmland, aquaculture, public green space, cemeteries, sports facilities and former landfill sites. An important part of this was the documentation of important local assets, such as Huế's traditional garden houses and the green spaces of former French colonial properties as distinctive, high biodiversity urban green assets that are being lost to modernisation and redevelopment pressure.

Building on this preparatory phase, the project held public participation events with experts and citizens, including policy roundtables in 2023 and 2024 where several scenarios for the future development of green and blue infrastructure were presented and discussed.

The first physical NbS showcases followed from 2024 onward, developed through a design competition with students and civil society representatives. They included the greening of a roof and façade on a cultural centre in Phú Hội, vertical garden elements at a schoolyard in An Đông, the upgrading of an existing public green space, and the conversion of a small riverside brownfield site into public green space. These small-scale, partly temporary interventions served as a testing ground for implementing NbS under local conditions in Huế. Among other things, they were used to increase the capacity of local stakeholders and urban planners. The project also launched a public Story Map so citizens can explore Huế's green and blue spaces online.

All these implementations were made to be aligned with the existing city level planning, such as Huế's 2016 city master plan and its 2030 targets for public green spaces per resident and the development of a new low-density “green district”.

Building on the insights gained during the research and development phase regarding the implementation of nature-based solutions as small-scale climate adaptation measures, the current implementation phase is driving forward the long-term establishment of nature-based solutions on two sites in the city of Huế.

This is taking place as part of a co-creation process in which detailed landscape architecture plans for the respective sites are being developed in collaboration with residents and stakeholders, with the involvement of a landscape architecture firm. These plans will subsequently be implemented by local stakeholders and are intended to make a long-term contribution to climate adaptation at both sites, as well as serving as inspiration and a blueprint for further similar projects in the city.

The project is funded by Germany's Federal Ministry of Research, Technology and Space (BMFTR, formerly BMBF) under the Research for Sustainable Development Programme (FONA), and implemented by an international consortium: UfU (lead partner), Humboldt-Universität zu Berlin, the Institute of Advanced Technology in Central Vietnam (IATC), the Thừa Thiên Huế Institute for Development Studies (HuếIDS), and the Faculty of Architecture at Huế University of Science, with HuếIDS specifically tasked with securing local financial contributions to the project.

• A status quo map with Huế's existing green and blue infrastructure that identifies both potential expansion areas on undeveloped land and potential upgrading areas in densely settled districts.
• Site-level modelling and four co-designed pilot interventions, such as the conversion of a riverside brownfield into public green space, showed that tree shade is the most effective cooling measure and that feasible nature based solutions can be delivered even with small land and budgets.
• A GIS model of the city identified priority areas for greening in planned urban expansion zones and assessed potential improvements to air quality, recreation and green space accessibility across Huế.
• The project supports existing public policy such as Huế's 2016 to 2030 master plan targets and the design of a new “eco-district”, alongside growing recognition of the economic and ecological value of the city's green heritage.
• Publication of a Green City Vision for Huế (2025) and a best practice handbook on green-blue infrastructure for urban heat adaptation in tropical Southeast Asian cities (2024), translating the project's findings into transferable guidance for other cities.
• Planning and long-term implementation of nature-based solutions in two selected areas within the city of Huế
• Capacity-building to ensure the long-term integration of nature-based solutions into urban development in Huế as effective, small-scale measures for adapting to more extreme weather conditions caused by climate change

• Loss of historic green assets: Huế's traditional garden houses and the green spaces of former French colonial properties are increasingly disappearing due to economic pressure, changes in building use and modernisation trends.
• Uneven distribution of green space: although Huế's per capita green space is relatively high, green and blue areas are not evenly distributed across the city, and access is particularly limited in the city centre.
• Competing economic and development interests: rapid urbanisation, population growth and the desire for economic growth create pressure toward denser, more conventional development that risks repeating patterns seen in other Southeast Asian cities such as Ho Chi Minh City and Hanoi.
• Informal settlement growth: high housing demand and limited availability of formal housing have led to a growing number of informal residential buildings, often in flood exposed areas.
• Financing and long term implementation: scaling up nature based solutions requires sustained investment and competes with other economic interests; governments, international donors and private investors need to recognise the value of nature based solutions and provide adequate funding.
• Governance gaps: the project's own policy analysis found insufficient policies, lack of expertise, poor coordination between agencies and limited public awareness as additional obstacles to effective NbS implementation in Huế, alongside the funding constraints noted above.
• Budgetary constraints faced by local authorities in Vietnam

• Small, distributed green interventions across a city can be more effective for local climate regulation and air quality than a few large parks.
• Preserving existing historic and cultural green assets can be as important as creating new green infrastructure, since these features already deliver significant ecosystem services and cultural and tourism value.
• The project found that strong leadership as well as citizen’s input on the maintenance of green spaces are key points for scaling NbS beyond the showcase sites. They must be built through co-design and co-learning with local stakeholders and experts.
• Nature based solutions can be a comparatively low cost and technically accessible climate investment for cities with limited financial and technical resources, making the approach particularly relevant for cities in the Global South, and Huế's approach in particular is presented as a potential model for other Southeast Asian cities seeking a more sustainable and climate resilient urbanisation pathway.

Stolpe, F. (2021). Ein Labor fuer oekologische Staedte: Naturbasierte Loesungen fuer Klimaschutz und Klimaanpassung in der vietnamesischen Stadt Huế. Oekologisches Wirtschaften, 36(3), 35 to 38. DOI 10.14512/OEW360335.

Stolpe, F., Hoang, T. B. M., Nguyen, D. H. L. (2023). Staerkung der Klimaresilienz in der vietnamesischen Stadt Huế: Naturbasierte Loesungen zur Reduzierung von Hitzestress und zur Verbesserung der Luftqualitaet. Transforming Cities, 3/2023, 61 to 65.

Roesler, K., Konopatzki, P., Jache, J., Hoang, T. B. M., Nguyen, D. H. L., Scheuer, S., Sumfleth, L., Stolpe, F., Haase, D. (2020). Nature based solutions in the city of Huế. Status Quo Report. www.greencitylabhue.com/status-quo-report/

Decision No. 649/QD-TTg. The Approval of the adjustment of Huế City's master planning to 2030 with a vision to 2050.