Mainstreaming climate change adaptation into urban planning: greyfield land redevelopment in Jena (Germany)

Jena (Thuringia, ~108,000 inhabitants) sits in a valley ringed by limestone slopes that trap heat, making it one of the warmest cities in central Germany and prone to a persistent urban heat island. Climate projections point to a further 3-6°C rise in summer maximum temperatures by 2100 and a large increase in hot days.

Under the JenKAS (Jena Climate Adaptation Strategy, developed 2009-2012), the city sought to mainstream climate adaptation into urban planning, applying it first to the redevelopment of Inselplatz, a 3-hectare inner-city parking area, into a new university campus, using a multi-criteria economic assessment to choose the best-performing design.

JenKAS produced a climate-sensible planning handbook and the JELKA decision-support tool. For Inselplatz, JELKA pre-selected adaptation options for three design drafts, which were then compared using the probabilistic multi-criteria tool PRIMATE/PROMETHEE II across heat-stress, cost, architectural quality and amenity criteria, modelled for the years 2021, 2021-2050 and 2071-2100.

The preferred design (more/larger-crowned trees, light-coloured pavement, 70% green roofing, an 80m2 water body) scored a lower modelled heat-stress index (6.7 by 2071-2100) than the two alternatives (7.5 and 7.2). The wider redevelopment project totals EUR 188 million, including about EUR 84 million from the European Regional Development Fund, EUR 10 million from federal Higher Education Pact funds, EUR 37.7 million from state funds and EUR 4.1 million from the city.

Mainstreaming was helped by public awareness after extreme weather, dedicated city staff and budget, national funding for the JenKAS tools, and a cross-institutional working group. Climate-change denial among some stakeholders, tight budgets, scarce experienced personnel and limited awareness of funding options were identified as constraints.