This book provides the first comprehensive and critical examination of the spatial assumptions underpinning transboundary protected areas in Europe, at a time of surging global enthusiasm in creating and managing such areas. It explores how the reliance on the natural science approach to space within environmental planning has led to a return of exclusionary discourses, in paradoxical contrast to the stated claims of designing 'peace parks'. The book builds a much-needed link between the critical geopolitical literature on boundaries and social approaches to nature and hybridity. Drawing the Line is theoretically informed yet grounded in substantial fieldwork from sites in France, Germany, Italy, Poland, Romania, Slovakia and the Ukraine. It uses material from the field to build and question theoretical debates, moving beyond site-specific issues to wider patterns and trends.