Document and Context
This is a research article by Matteo Roggero, published by Taylor & Francis, on urban climate experimentation. It examines Berlin's attempt to become a sponge city, meaning a city that stores and reuses rainwater locally, through decentralized rainwater management (DRM). The paper contrasts two perspectives: planned scaling, where experiments are tested and then institutionalized city-wide, and permanent experimentation, where experiments remain context-dependent and are repeated rather than replicated.
Analytical Framework
The paper argues that the debate has treated the two approaches as generally superior or inferior, and proposes instead to relate them to context. It defines two dimensions: heterogeneity (the diversity of the urban fabric, social and biophysical) and capacity (the resources a local government has to institutionalize changes). Planned scaling is linked to low heterogeneity and high capacity, while permanent experimentation is linked to high heterogeneity and low capacity.
Methodology
The author conducts an in-depth case study of DRM in Berlin. Written sources, including city strategic plans and research articles, were reviewed from January to October 2022 to provide context. Between October 2022 and September 2023, the author carried out 15 interviews, comprising 2 academics, 2 officials, 4 practitioners, 1 civil society representative, 1 facility manager and 2 residents. Interviews were not recorded; the author relied on notes, a choice the paper describes as a trade-off between accuracy and richness.
Berlin Case Context
The paper notes Berlin's population growth from about 3.5 million at reunification to almost 4 million at present. It describes policy instruments including a rainwater fee, the Gründach Plus subsidy programme for green roofs and façades, mandatory DRM for new constructions and remodelling, and a Rainwater Agency established in 2019. Berlin's policy documents describe the city as an 'experimental field'.
Key Findings
Interviews portray Berlin as a high-heterogeneity, low-capacity context. Heterogeneity appears in the need for tailored retrofits, regulations that block multi-plot solutions, and a fragmented housing sector. Capacity problems include technical guidelines that do not integrate DRM, a risk-averse administrative culture, high staff turnover and sick leave, and vacancies that are hard to fill. The author concludes that planned scaling is out of reach and that Berlin can become a sponge city only through permanent experimentation, with intrinsic motivation of project initiators as the main bottleneck.
Implications for Policy
The paper suggests that the shift from requiring to enabling DRM is consistent with permanent experimentation. It argues that financial support is probably not the main limiting factor, and that the Rainwater Agency's narrow mandate prevents it from supporting individual projects. An expanded agency that mediates between initiators and officials could fill this gap.
Limitations and Scope
The author notes that analysing the whole city, rather than districts, and using a dichotomous framework may miss more nuanced processes. The paper states that permanent experimentation in Berlin has merit only under the specific contextual conditions identified.
Why It Matters for Urban Climate Policy
The paper addresses researchers and decision-makers working on urban climate action, and argues that scaling should be discussed as a context-dependent issue, bringing together research communities that are currently divided.