The ecological component is crucial in landscape planning according to the principles of sustainable development. We define “ecologically sustainable landscape” and develop a tool to measure how ecological sustainability is incorporated in landscape plans. This method acknowledges the critical role of spatial scale and pattern to the conservation of biodiversity. The metapopulation concept is used as a spatially explicit ecological theory, appropriate to describe the relation between biodiversity and the pattern of ecosystem patches (“ecosystem network”) in intensively used regions. We propose that ecological sustainability is achieved if quality, area and configuration of the ecosystem network permit target species to persist. A simple decision-making model represents a theoretical framework for a tool comprising two sets of ecological indicators. One set indicates the awareness of actors to consider ecological principles of sustainable planning. The other set indicates their performance to apply these principles quantitatively in designing the ecosystem pattern. The method is applied on a sample of reports on Dutch landscape development plans. A majority of the reports shows awareness of the importance of spatial conditions for achieving planning goals, but perform inadequately on the quantitative indicators. We conclude that the tool could be developed as a guideline and assessment method for the ecological sustainability of landscape plans.