For policy making and spatial planning, information is needed about the impacts of climate change on natural ecosystems. To provide this information, commonly hydrological and ecological models are used. We give arguments for our assessment that modelling only is insufficient for determining the impacts of climate changes on natural ecosystems at regional scales. Instead, we proposed a combination of hydrological simulations, a literature review and process-knowledge on climate-hydrology-vegetation interactions, to compile a sketch-map that indicates climate change effects on a number of ecosystems in The Netherlands. Soon after its introduction, copies of our sketch-map appeared in policy documents and in a commercial and popular atlas of The Netherlands. Moreover, the map led to a question in the Dutch parliament about the survivability of bog reserves in the future climate. Apparently, there was an urgent need for the information provided by the map.