Active versus passive restoration: Forests in the southern Carpathian Mountains as a case study

Active and passive restoration are both increasingly considered as options for nature recovery, with potential to help address the current climate and biodiversity crises. So far, however, there is little practical information on how to gauge the benefits and limitations of each approach, in terms of their effects on large-scale ecosystem composition, structure, and functioning. To address this knowledge gap, this study used satellite remote sensing to investigate changes in land cover and primary productivity within the forests of the Făgăraș Mountains in southern Romania, where large-scale restoration and land abandonment have simultaneously taken place across the past two decades. To our knowledge, this study is the first to contrast the impacts of active and passive restoration within a single landscape on components of ecosystem structure and functioning at such temporal and spatial scales. Results show active restoration activities to be very effective at facilitating the recovery of cleared forests in small parts of the landscapes; but they also highlight substantial areas of natural forest expansion following agricultural abandonment, in line with regional trends. Altogether, our approach clearly illustrates how freely available satellite data can (1) provide vital spatially explicit insights about large-scale and long-term transformations in ecosystem composition, structure and functioning; and (2) help contrast the impacts of restoration approaches on vegetation distribution and dynamics, in ways that complement existing ground-based studies.