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Aims: Primary forests are critical for forest biodiversity and provide key ecosystem services. In Europe, these forests are particularly scarce and it is unclear whether they are sufficiently protected. Here we aim to: (a) understand whether extant primary forests are representative of the range of naturally occurring forest types, (b) identify forest types which host enough primary forest under strict protection to meet conservation targets and (c) highlight areas where restoration is needed and feasible. Location: Europe. Methods: We combined a unique geodatabase of primary forests with maps of forest cover, potential natural vegetation, biogeographic regions and protected areas to quantify the proportion of extant primary forest across Europe's forest types and to identify gaps in protection. Using spatial predictions of primary forest locations to account for underreporting of primary forests, we then highlighted areas where restoration could complement protection. Results: We found a substantial bias in primary forest distribution across forest types. Of the 54 forest types we assessed, six had no primary forest at all, and in two‐thirds of forest types, less than 1% of forest was primary. Even if generally protected, only ten forest types had more than half of their primary forests strictly protected. Protecting all documented primary forests requires expanding the protected area networks by 1,132 km2 (19,194 km2 when including also predicted primary forests). Encouragingly, large areas of non‐primary forest existed inside protected areas for most types, thus presenting restoration opportunities. Main conclusion: Europe's primary forests are in a perilous state, as also acknowledged by EU's "Biodiversity Strategy for 2030." Yet, there are considerable opportunities for ensuring better protection and restoring primary forest structure, composition and functioning, at least partially. We advocate integrated policy reforms that explicitly account for the irreplaceable nature of primary forests and ramp up protection and restoration efforts alike. [ABSTRACT FROM AUTHOR]

Forest composition is a faithful indicator of the stressors and disturbances that influence forest ecosystems, and it should be accounted for in Sustainable Forest Management policies. Indeed, the classification of forest ecosystems in forest types is considered as a key tool to improve the assessment and monitoring of forest biological diversity, and for the definition of management guidelines. Accordingly, the Ministerial Conference on the Protection of Forests in Europe has recognized the need of developing a pan-European forest classification in forest types, and has identified indicators of Sustainable Forest Management that should be applied by forest types. The classification of vegetation has always been among the main aims of the plant sociology. The quantitative and qualitative analysis of plant species composition, performed through the plant sociological approach, condenses compositional and structural information within a hierarchical system, and expresses all historical, sociological and habitat factors that influence the actual and potential vegetation. In a modern perspective the integration of plant sociology and ecological analysis represents a key to a hierarchical land classification and to the understanding of vegetation dynamics; furthermore the long history of plant sociology determined the availability of large datasets of vegetation data throughout Europe. Starting from these considerations, in this paper we briefly describe how plant sociology could represent a tool for the assessment of the indicators of SFM that should be applied by forest types, giving insights on how this discipline could contribute to the assessment of each of these indicators. [ABSTRACT FROM AUTHOR]

[Display omitted] • Forest multi-taxon studies have similar aims but different sampling protocols. • The most sampled taxonomic groups are plants, beetles, lichens, birds, fungi. • Soil, litter and canopy resulted as undersampled forest habitats. • Sampling units and substrates differed widely within and among taxonomic groups. • Sampling methods for stand structure were relatively homogeneous. Forests host most terrestrial biodiversity and their sustainable management is crucial to halt biodiversity loss. Although scientific evidence indicates that sustainable forest management (SFM) should be assessed by monitoring multi-taxon biodiversity, most current SFM criteria and indicators account only for trees or consider indirect biodiversity proxies. Several projects performed multi-taxon sampling to investigate the effects of forest management on biodiversity, but the large variability of their sampling approaches hampers the identification of general trends, and limits broad-scale inference for designing SFM. Here we address the need of common sampling protocols for forest structure and multi-taxon biodiversity to be used at broad spatial scales. We established a network of researchers involved in 41 projects on forest multi-taxon biodiversity across 13 European countries. The network data structure comprised the assessment of at least three taxa, and the measurement of forest stand structure in the same plots or stands. We mapped the sampling approaches to multi-taxon biodiversity, standing trees and deadwood, and used this overview to provide operational answers to two simple, yet crucial, questions: what to sample? How to sample? The most commonly sampled taxonomic groups are vascular plants (83% of datasets), beetles (80%), lichens (66%), birds (66%), fungi (61%), bryophytes (49%). They cover different forest structures and habitats, with a limited focus on soil, litter and forest canopy. Notwithstanding the common goal of assessing forest management effects on biodiversity, sampling approaches differed widely within and among taxonomic groups. Differences derive from sampling units (plots size, use of stand vs. plot scale), and from the focus on different substrates or functional groups of organisms. Sampling methods for standing trees and lying deadwood were relatively homogeneous and focused on volume calculations, but with a great variability in sampling units and diameter thresholds. We developed a handbook of sampling methods (SI 3) aimed at the greatest possible comparability across taxonomic groups and studies as a basis for European-wide biodiversity monitoring programs, robust understanding of biodiversity response to forest structure and management, and the identification of direct indicators of SFM. [ABSTRACT FROM AUTHOR]