This article addresses the differentiated impacts of various sectors and branches in a multi-layer spatial system. The key question is whether in an interdependent spatial system - comprising a local, regional and national component - one or more core industries or sectors can be identified that may act as strategic handles for long-range sustainable development of a local economy. As a case study, the Cairngorms National Park in Scotland is used. In this area, policy makers - at different administrative levels - strongly emphasize the need for new sustainable economic development. We use a novel combination of stakeholder analysis (with household questionnaires) and multi-level interregional input-output analysis to identify which critical local key sectors are acting as carriers for local sustainability. The methodological vehicle employed in our study is based on microsimulation, as a tool to cope with limited data availability. This paper demonstrates how, even for small areas such as the Cairngorms National Park in Scotland, survey information combined with secondary data and existing input-output tables can be integrated into a useful policy toolbox for local sustainable development in a broader regional-national context.