Systematic Map Protocol Examines Metrics for Tracking Temperate Ecosystem Restoration

A research team led by Kerstin Bouma and Jacob Heilmann-Clausen has published a comprehensive systematic map protocol in the journal Environmental Evidence to establish a rigorous methodological framework for identifying and evaluating the metrics used to assess dynamic nature management across temperate ecosystems. Co-authored by Pablo Villalva Aguilar, Siri Vatsø Haugum, Bjarke Madsen, Urs Albert Treier, Signe Normand, and Carsten Rahbek, the protocol outlines a planned synthesis designed to investigate what evidence exists regarding the impact of restoring natural ecological processes on biodiversity. As documented in the study protocol, modern conservation practice is undergoing an operational paradigm shift away from static preservation approaches that safeguard specific species or historical habitat states toward dynamic conservation strategies that restore self-sustaining natural processes. Because initiatives rooted in open-ended restoration, forward-looking restoration, and rewilding establish conditions for self-organizing ecosystems that evolve toward unpredictable future states, standardizing measurable and generalizable indicators remains an unresolved operational hurdle for conservation managers charged with tracking dynamic interventions.

The published protocol responds directly to practical monitoring dilemmas highlighted through collaborative engagements with Danish conservation practitioners, including land managers from the Aage v. Jensen Naturfund who oversee diverse habitat networks across Denmark. These practitioners identified a substantial knowledge gap in existing guiding, monitoring, and reporting frameworks, emphasizing that current tools rarely accommodate the inherent stochasticity, natural disturbances, and non-linear trajectories characteristic of self-organizing ecological systems. While established conceptual frameworks, such as the two-pillar model proposed by Torres and colleagues, define rewilding progress in terms of decreasing human forcing of natural processes and increasing ecological integrity, the authors note that these high-level theoretical constructs are not directly translatable into standardized field observations. Earlier quantification efforts have examined varied dimensions including trophic complexity, landscape metrics, ecosystem structure, and biophysical processes, yet the practical field indicators required to validate these concepts remain ambiguous, hindering consistent reporting, goal setting, and evidence-based nature management.

To bridge the divide between theoretical restoration concepts and field-level monitoring, the planned systematic map establishes strict eligibility criteria structured around population, intervention, comparator, and outcome parameters defined under the Collaboration for Environmental Evidence Guidelines. The geographic population encompasses natural areas located within temperate climate zones delineated by the Köppen-Geiger climate classification system, explicitly including boreal and Mediterranean zones due to their comparable ecological conditions and extensive literature bases, while strictly excluding tropical, polar, desert, and alpine ecosystems to maintain analytical tractability. The eligible interventions comprise active restoration or spontaneous re-establishment of core natural dynamics, specifically targeting process restoration involving herbivory and browsing regimes, hydrology and water level fluctuations, natural or prescribed fire disturbances, and forest gap dynamics. Eligible comparators must provide explicit temporal or spatial contrasts, requiring before-and-after monitoring, control-and-impact contrasts, or integrated before-after-control-impact experimental designs.

The methodological framework details an exhaustive multi-stage search strategy across international bibliographic indexing services, academic dissertations, and specialized grey literature repositories to ensure comprehensive evidence retrieval. The primary bibliographic search interrogates Web of Science Core Collection across all citation indices using topic terms, Scopus across titles, abstracts, and keywords, and Agricola via the Ovid interface using keyword fields. Preliminary search executions conducted during protocol development yielded 3,852 candidate records in Web of Science, 3,032 records in Scopus, and 1,306 records in Agricola, resolving to 5,232 unique articles after systematic deduplication. To prevent academic publication bias, the investigators will search ProQuest to identify relevant doctoral dissertations and query Google Scholar through Publish or Perish software, screening the first 200 ranked entries against a condensed search string that captures rewilding, disturbance, and biodiversity terms, with scheduled annual search updates on the first of January.

Recognizing that substantial empirical documentation of dynamic nature management resides outside commercial academic journals, the protocol specifies targeted grey literature screening across twenty-six governmental, academic, and non-governmental organizational platforms. This institutional search encompasses international and regional bodies across Europe, including Dutch organizations such as Ontwikkeling en Beheer Natuurkennis, Staatsbosbeheer, Natuurmonumenten, and ARK Rewilding, alongside European initiatives such as Rewilding Europe and EU-LIFE projects. The search protocol incorporates Danish bodies such as Aage v. Jensen Naturfund, Saksfjed Wilderness, Naturstyrelsen, and the DCE National Centre for Environment and Energy, alongside Norwegian institutional repositories including the Bergen Open Research Archive, the Norwegian Institute of Bioeconomics, the Norwegian Institute of Nature Research, the Norwegian Environment Agency, NTNU Open, UiO DUO, the Norwegian University of Life Sciences, and UiT Munin. Swedish repositories include the Swedish University of Agricultural Sciences, the Swedish Environmental Protection Agency, and Skogforsk, while Spanish holdings incorporate CSIC, Estación Biológica de Doñana, MITECO, Organismo Autónomo Parques Nacionales, and CREAF.

Language parameters for the systematic map have been configured to support linguistic breadth across the grey literature while maintaining rigorous standards across peer-reviewed bibliographic outputs. While formal bibliographic database searches are restricted to English-language journal articles and review papers, the grey literature search across organizational websites and web-based search engines evaluates documentation published in English, Spanish, Danish, Norwegian, Swedish, Dutch, and German. Review articles identified through these searches will not be incorporated directly into the systematic map as primary evidence units; instead, their reference lists will be examined systematically to trace additional eligible primary field studies. Preliminary validation procedures confirmed the sensitivity and precision of the retrieval strategy, demonstrating that the formulated search strings successfully retrieved all predefined benchmark articles during pilot verification across Web of Science, Scopus, Agricola, and Google Scholar.

Article screening will follow a structured dual-reviewer workflow managed through the COVIDENCE software environment to ensure procedural transparency and minimize individual selection bias. Following automated and manual deduplication, all identified records will undergo title and abstract screening against predefined inclusion criteria, with reviewers instructed to resolve borderline ambiguities through inclusion to enable full-text appraisal. Consistency among the review team will be calibrated prior to full screening by conducting an independent pilot review of 50 randomly selected studies across approximately six team members, calculating Cohen’s kappa coefficients to ensure inter-rater agreement exceeds the accepted threshold value of 0.6. Following this pilot, title and abstract screening as well as subsequent full-text evaluations will be executed independently by two reviewers, with disagreements resolved through consensus discussions or adjudicated by an independent third reviewer via majority vote.

The study protocol outlines a dedicated validity assessment process to evaluate risk of bias across all primary empirical studies that successfully pass full-text eligibility screening. Each included study will undergo structured critical appraisal using the standardized critical appraisal tool issued by Environmental Evidence, which evaluates study design, experimental execution, and potential sources of systematic error. Based on this formal evaluation, primary studies will be classified into high, medium, or low susceptibility to bias, with the protocol mandating the total exclusion of studies categorized as exhibiting high susceptibility to bias from the final evidence synthesis. Appraisals will be conducted independently by two reviewers, resolving differing assessments through consensus meetings or the decisive input of a third reviewer, while strict procedural independence rules prevent any author from reviewing or appraising their own research publications.

Reviewers will systematically code metadata describing the monitoring period, sampling start and end dates, sampling frequency, and total time elapsed since restoration interventions or spontaneous development commenced. The data extraction template records specific ecosystem categories, including terrestrial habitats and aquatic-terrestrial ecotones such as forests, grasslands, heathlands, dunes, peatlands, and riparian zones, while excluding purely marine or strictly aquatic systems. Coded parameters will document study designs across before-and-after, control-and-impact, and BACI configurations, implemented restoration actions, underlying ecological drivers, observed direction of response, exact geographic coordinates or locality centroids, plot dimensions, sampling configurations, spatial scale spanning local to global extents, and detailed historical land-use baselines.

Synthesizing these extracted parameters, the systematic map will structure biodiversity outcomes across four primary metric domains: spatial metrics, functional traits and functional guilds, structural indices, and species composition measurements across diverse taxonomic groups. The planned synthesis will map recorded metrics across plants, birds, insects, fish, terrestrial invertebrates, reptiles, amphibians, fungi, and microorganisms, while incorporating technological monitoring tools such as satellite imagery, LiDAR, environmental DNA, and automated image detection. Conforming strictly to the ROSES reporting standards, the resulting systematic map will combine narrative synthesis with geographical distributions, ecosystem matrices, and process-specific evidence clusters to pinpoint critical empirical knowledge gaps. By pairing this structural mapping with time-and-cost assessments for individual monitoring approaches, the authors aim to deliver a practical decision-support guide for conservation managers evaluating dynamic restoration across temperate landscapes.

Subject of Research: Systematic map protocol for biodiversity metrics in dynamic temperate ecosystem restoration

Article Title: What evidence exists for the impact of restoration of natural processes on biodiversity in temperate ecosystems: a systematic map protocol

Article References: Bouma, K., Villalva Aguilar, P., Haugum, S. V., Madsen, B., Treier, U. A., Normand, S., Rahbek, C., & Heilmann-Clausen, J. (2025). What evidence exists for the impact of restoration of natural processes on biodiversity in temperate ecosystems: a systematic map protocol. Environmental Evidence, 14(1), Article 18. https://doi.org/10.1186/s13750-025-00373-6

Image Credits: AI Generated

DOI: 10.1186/s13750-025-00373-6

Keywords: systematic map protocol, rewilding, biodiversity metrics, temperate ecosystems, ecological restoration, Environmental Evidence, nature management, conservation monitoring, evidence, exists, impact, restoration