Free and Hanseatic City of Hamburg – Ministry of Environment and Energy; General Directorate of Nature Conservation, Landscape Architecture & Energy Division; NGE1 Landscape Planning and Urban Green PNEC – Association of Municipalities Polish Network „Energie Cités“ GRAD – Grüne Dächer für die Anpassung an den Klimawandel in städtischen Räumen Reise über Hamburgs Gründächer