A balancing act: Principles, criteria and indicator framework to operationalize social-ecological resilience of forests

Biodiversity and Management as Central Players in the Network of Relationships Underlying Forest Resilience

Global change is threatening the integrity of forest ecosystems worldwide, amplifying the need for resilience-based management to ensure their conservation and sustain the services they provide. Yet, current efforts are still limited by the lack of implementation of clear frameworks for operationalizing resilience in decision-making processes. To overcome this limitation, we aim to identify reliable and effective drivers of forest resilience, considering their synergies and trade-offs. From a comprehensive review of 342 scientific articles addressing resilience in forests globally, we identified factors shaping forest resilience. We recognized them into two categories that influence forest responses to disturbances: resilience predictors, which can be modified through management, and codrivers, which are measurable but largely unmanageable (e.g., climate). We then performed network analyses based on predictors and codrivers underlying forest resilience. In total, we recognized 5332 such relationships linking predictors or codrivers with forest attributes resilience. Our findings support the central role of biodiversity, with mixed, non-planted, or functionally diverse forests promoting resilience across all contexts and biomes. While management also enhanced resilience, the success of specific interventions was highly context-dependent, suggesting that its application requires a careful analysis of trade-offs. Specifically, practices like cutting and prescribed burning generally enhanced resilience in terms of tree growth, plant diversity, landscape vegetation cover, and stand structure. In contrast, pest and herbivore control reduced the resilience of plant taxonomic diversity while offering only minimal gains for other variables. Even long-term restoration projects showed clear trade-offs in the resilience of different forest attributes, highlighting the need for careful consideration of these effects in practical management decisions. Overall, we emphasize that a reduced number of predictors can be used to effectively promote forest resilience across most attributes. Particularly, enhancing biodiversity and implementing targeted management strategies when biodiversity is impoverished emerge as powerful tools to promote forest resilience.

Quantifying the impacts of rewilding on ecosystem resilience to disturbances: A global meta-analysis

Rewilding is one approach to restoration that aims at restoring natural self-sustaining ecosystems, allowing natural processes to resume by targeting an increase in trophic complexity, disturbance stochasticity, and dispersal, while minimizing human interventions. These components have also been argued to enhance ecosystem resilience, yet this claim has barely been specifically addressed. We conducted a meta-analysis to explore whether rewilding interventions aimed at increasing biodiversity (i.e., trophic complexity), disturbance stochasticity or connectivity increase ecosystem resilience to future abiotic and biotic disturbances. We integrated two recently developed operational frameworks to address rewilding and resilience and scrutinized the outcomes of 42 case studies (305 observations). We found that, overall, the three abovementioned rewilding components increased resilience of variables related to demography, biodiversity, biophysical characteristics and the disturbance regime characteristics (70% of observations). Yet, this result was influenced by the nature of the disturbance and the resilience approach, with lower success reported for abiotic disturbances (drought and fire) and social-ecological resilience. While interventions targeting only disturbance stochasticity or biodiversity and disturbance stochasticity together showed positive effects, interventions targeting the trophic complexity alone contributed less to system variables related to biodiversity. The most common rewilding interventions, such as domestic and wild herbivore introductions and invasive plant removals, enhanced resilience towards biotic disturbances (i.e., invasions). We also found that some particular resilience contexts (social-ecological systems) lack sufficient observations to allow clear conclusions. Overall, our results empirically demonstrate the predominantly positive effects of rewilding on ecosystem resilience, underpinning the potential of this approach for preparing ecosystems for the uncertain effects of increasing climate change and associated disturbances yet acknowledging some limitations depending on the nature of the disturbance.

Patterns of early post-disturbance reorganization in Central European forests

Disturbances catalyse change in forest ecosystems, and a climate-driven increase in disturbance activity could accelerate forest reorganization. Here, we studied post-disturbance forests after the biggest pulse of tree mortality in Central Europe in at least 170 years, caused by drought and bark beetle (Scolytinae) outbreaks in 2018-2020. Our objectives were to characterize the early state of tree regeneration after mortality, quantify patterns of reorganization relative to undisturbed reference conditions and assess how management and patch size affect forest reorganization after disturbance. We surveyed 1244 plots in 120 patches under managed (salvage-logged, often planted) and unmanaged (deadwood remaining on site, no planting) conditions in Germany. We found that regeneration density on disturbed sites was high (median 11 897 stems ha-1), resulting from a cohort of advance regeneration. Disturbances were strong drivers of change, with indications for resilience on only 36.3% of patches. Reassembly (i.e. a change in species composition) was the dominant pattern of reorganization (61.5%), and Picea abies forests changed most strongly. Post-disturbance management facilitated forest change, particularly promoting a change in species composition. The strength of reorganization increased with patch size. We conclude that the recent wave of tree mortality will likely accelerate forest change in Central Europe.

Shaping and enhancing resilient forests for a resilient society

The world is currently facing uncertainty caused by environmental, social, and economic changes and by political shocks. Fostering social-ecological resilience by enhancing forests' ability to provide a range of ecosystem services, including carbon sequestration, habitat provision, and sustainable livelihoods, is key to addressing such uncertainty. However, policy makers and managers currently lack a clear understanding of how to operationalise the shaping of resilience through the combined challenges of climate change, the biodiversity crisis, and changes in societal demand. Based on a scientific literature review, we identified a set of actions related to ecosystem services, biodiversity conservation, and disturbance and pressure impacts that forest managers and policy makers should attend to enhance the resilience of European forest systems. We conclude that the resilience shaping of forests should (1) adopt an operational approach, which is currently lacking, (2) identify and address existing and future trade-offs while reinforcing win-wins and (3) attend to local particularities through an adaptive management approach.

Resilience and vulnerability: distinct concepts to address global change in forests

Resilience and vulnerability are important concepts to understand, anticipate, and manage global change impacts on forest ecosystems. However, they are often used confusingly and inconsistently, hampering a synthetic understanding of global change, and impeding communication with managers and policy-makers. Both concepts are powerful and have complementary strengths, reflecting their different history, methodological approach, components, and spatiotemporal focus. Resilience assessments address the temporal response to disturbance and the mechanisms driving it. Vulnerability assessments focus on spatial patterns of exposure and susceptibility, and explicitly address adaptive capacity and stakeholder preferences. We suggest applying the distinct concepts of resilience and vulnerability where they provide particular leverage, and deduce a number of lessons learned to facilitate the next generation of global change assessments.

Urban landscape sustainability in karst mountainous cities: A landscape resilience perspective

In the context of the rapid progress of global urbanization, the massive encroachment of social landscapes into ecological and productive landscapes has led to a series of environmental problems. Furthermore, analyzing the landscape resilience could effectively reveal the sustainable development ability of the urban landscape. This study establishes a social-ecological productive landscape resilience (SEPLR) evaluation system and reveals trade-offs and synergies between different landscape types and resilience. Finally, this study provides landscape management zonings based on the spatial and temporal dynamic characteristics of landscape resilience and subsystem resilience. The findings showed that: (1) The CUAG has significant landscape heterogeneity and change drastically, which is mainly manifested by the massive encroachment of social landscape into productive landscape. (2) The SEPLR of CUAG decreased slightly by 0.75 % over the decade, with significant changes of spatial distribution. (3) The comprehensive remediation areas and social development areas are the dominant management zones. The findings could be incorporated into the decision-making of land use trade-off development in CUAG to promote the coordinated development of social-ecological productive systems and improve the sustainability of urban landscape.

The interacting effect of climate change and herbivory can trigger large-scale transformations of European temperate forests

In many regions of Europe, large wild herbivores alter forest community composition through their foraging preferences, hinder the forest's natural adaptive responses to climate change, and reduce ecosystem resilience. We investigated a widespread European forest type, a mixed forest dominated by Picea abies, which has recently experienced an unprecedented level of disturbance across the continent. Using the forest landscape model iLand, we investigated the combined effect of climate change and herbivory on forest structure, composition, and carbon and identified conditions leading to ecosystem transitions on a 300-year timescale. Eight climate change scenarios, driven by Representative Concentration Pathways 4.5 and 8.5, combined with three levels of regeneration browsing, were tested. We found that the persistence of the current level of browsing pressure impedes adaptive changes in community composition and sustains the presence of the vulnerable yet less palatable P. abies. These development trajectories were tortuous, characterized by a high disturbance intensity. On the contrary, reduced herbivory initiated a transformation towards the naturally dominant broadleaved species that was associated with an increased forest carbon and a considerably reduced disturbance. The conditions of RCP4.5 combined with high and moderate browsing levels preserved the forest within its reference range of variability, defining the actual boundaries of resilience. The remaining combinations of browsing and climate change led to ecosystem transitions. Under RCP4.5 with browsing effects excluded, the new equilibrium conditions were achieved within 120 years, whereas the stabilization was delayed by 50-100 years under RCP8.5 with higher browsing intensities. We conclude that forests dominated by P. abies are prone to transitions driven by climate change. However, reducing herbivory can set the forest on a stable and predictable trajectory, whereas sustaining the current browsing levels can lead to heightened disturbance activity, extended transition times, and high variability in the target conditions.