Understanding how invasive species cope with novel thermal environments can help clarify the physiological mechanisms supporting establishment and range expansion. Here, we measured resting metabolic rate in captive-bred common waxbills (Estrilda astrild), a successful Afrotropical invader, across ambient temperatures ranging from 11 to 35 °C. We also assessed individual metabolic reaction norms, repeatability, core body temperature and thermal conductance to determine whether birds followed classical thermoregulatory expectations or showed evidence of reduced energetic costs at low temperatures. Metabolic rate showed a non-linear relationship with ambient temperature, with a lower critical temperature at ∼28.9 °C and a second inflection at ∼18.8 °C. Below this second threshold, metabolic rate levelled off rather than increasing linearly as predicted by the Scholander-Irving model. This pattern coincided with lower thermal conductance at colder temperatures and modest reductions in body temperature, suggesting that the deviation cannot be attributed to metabolic downregulation alone. Individuals differed consistently in overall metabolic level, but showed little evidence of consistent differences in reaction-norm slopes. Together, these results suggest that common waxbills may reduce thermoregulatory costs under mild cold exposure through coordinated physiological adjustments, a flexibility that may contribute to their persistence in cooler invaded environments.

The invasive yellow-legged hornet ( Vespa velutina ), listed as a species of Union concern under Regulation (EU) No 1143/2014, has rapidly expanded across Europe since 2004. It impacts human health, biodiversity, and agriculture. Understanding its population dynamics is essential for designing effective management strategies. In recent years, citizen science initiatives have generated large datasets that can support quantitative modelling of the population. We developed an individual-based population model for V. velutina using long-term data from the Vespa-Watch platform in Flanders (Belgium). The model was parameterized using annual counts of nests recorded since 2016. By simulating the life cycle of queens and their contribution to population growth, the model allows us to explore the effects of current management efforts on population development, as well as future population trajectories under different management scenarios across space (at level of Flanders, provinces or municipalities) and various intensities of nest removal. Our results highlight the value of citizen science data alongside the reporting of management interventions for modelling the dynamics of invasive species and for evaluating management strategies. The modelling framework provides a quantitative tool to assess the effectiveness of control measures and supports evidence-based management of V. velutina populations in Flanders and elsewhere in Europe.

Invasive predators are one of several factors contributing to insect decline. Their trophic impacts on native communities remain poorly quantified. The yellow-legged hornet ( Vespa velutina ) is an invasive predator that has rapidly expanded across Europe and is considered a potential threat to native insects, particularly pollinators. However, despite increased research attention, the composition of its diet and its preferences for certain prey remain poorly characterised beyond broad taxonomic categories. In addition, how foraging strategies vary across seasons or habitats remains poorly understood. This information is crucial to help quantify predation pressure on specific insect populations, which is critical for understanding impacts on native pollinators. Here, we investigate the diet of Vespa velutina across Flanders (northern Belgium) using DNA metabarcoding of larval gut contents. Our dataset includes over 4,800 dissected larvae from 224 nests collected between April and October 2025, with samples homogenised at the nest level. Preliminary results reveal a broad prey spectrum across multiple insect groups, dominated by Diptera, Hymenoptera, Orthoptera, and Coleoptera. Although the metabarcoding does not allow quantitative estimates of prey biomass or prey numbers, our results show the species exhibits high taxonomic diversity in its diet including functional groups such as pollinators, parasitoids and decomposers. Notably, Pipiza lugubris and Cheilosia illustrata , two hoverfly species listed as vulnerable on the Flemish Red List (2021), were detected in 3 and 8 nests respectively, confirming V. velutina predation on species of conservation concern. Our results also indicate seasonal shifts in diet composition, illustrating flexible foraging strategies. These high-resolution insights into the trophic ecology of V. velutina help assess its potential environmental impact on native biodiversity.

Forest structural complexity is widely assumed to enhance biodiversity, yet its effects on the physiological condition and health of individual organisms remain poorly understood. We examined how forest structural complexity relates to individual condition and, in turn, to ectoparasite and pathogen occurrence in free-living vertebrates. Across 19 temperate forest plots in Flanders (northern Belgium), spanning a gradient of structural complexity, we sampled birds and small mammals and quantified individual condition using scaled mass index, fluctuating asymmetry, and relative telomere length. Larval ticks were collected from hosts and screened for a broad panel of tick-borne pathogens. Relative telomere length tended to be lower in more structurally complex forests, whereas body condition and fluctuating asymmetry showed no consistent relationship with forest structure. Individuals in better body condition were less likely to carry larval ticks. In contrast, hosts with shorter telomeres were more likely to carry pathogen-infected larvae, consistent with links between cumulative physiological stress and infection susceptibility. No evidence was found for systematic co-occurrence among pathogens within larval ticks. Together, our results indicate that individuals interact with forest structure through multiple, potentially independent physiological pathways, shaping observed patterns of parasite load and tick-borne pathogen prevalence.

Increasing forest structural complexity is a key objective of future-proof forest management, with benefits for biodiversity. However, empirical evidence for generalizable biodiversity-structure relationships across taxa is still limited. We investigated whether structurally more complex forests support greater species richness within individual taxa and higher multidiversity (i.e. a composite diversity metric) across taxonomic and functional groups in 19 mature forest plots in Flanders, Belgium. As one of the most densely populated regions in Europe, Flanders provides a realistic and policy-relevant context to test structure-biodiversity relationships, despite not capturing old-growth forest conditions. Its forests, often dominated by a few tree species and subject to long-term anthropogenic pressures and management, represent a realistic gradient of structural complexity. Structural complexity was quantified using a Structural Complexity Index (SCI), and biodiversity was assessed using a multidiversity index integrating scaled species richness across five taxonomic and seven arthropod functional groups, as well as the species richness of individual groups. Using mixed-effects models and multivariate Bayesian analyses, we tested both direct effects of SCI on biodiversity and the covariation in species richness among groups. Contrary to expectations, SCI was not a consistent predictor of multidiversity, and most groups showed weak or inconsistent responses. These findings might suggest that, within the range of structural complexity currently present in managed forests, structural complexity alone may be insufficient to enhance biodiversity in simplified forests.

Following an incursion of a previously absent invasive alien species (IAS), the window of opportunity for successful eradication is often limited, requiring a rapid and coordinated response. Success depends heavily on the efficient and timely transition from detection to action. Contingency planning is a key component in this process, providing a structured framework for preparedness and action. Unlike long-term management strategies for established invasive populations, a contingency plan ensures that the necessary procedures, resources, and legal mandates are in place before an introduction occurs. These plans define the roles and responsibilities of relevant parties, ensuring seamless cooperation during time-sensitive scenarios. Furthermore, contingency planning is essential for regulatory compliance. For instance, under EU Regulation No 1143/2014, Member States are mandated to act immediately to eradicate species of Union Concern upon detection in new territories. Without prior planning, administrative, legal, or logistical delays can allow a nascent invasive population to expand beyond the point of feasible control. Despite their recognised importance, contingency planning in the context of biological invasions remains limited (Early et al. 2016), and existing plans vary considerably in structure and level of detail. To address this, we conducted a semi-structured review of academic and grey literature to gather a comprehensive and representative cross-section of accessible, international resources on contingency planning. We analysed the implementation of these contingency plans across time, geographic region, and taxonomic group, and identified important recurring elements. Sixty contingency plans were identified, mainly English-language resources from the United States, the United Kingdom and Australia. The majority of these plans target groups of species, most often from freshwater (43%) or marine (28%) environments. An overall increase in the use of contingency plans was observed over time, particularly in recent years. Plans differed considerably in structure and content, highlighting the need for a more uniform and accessible approach. Based on this, we developed a practical guideline for drafting IAS contingency plans. Three possible approaches were identified: a species-specific, group-based or generic plan. For each, the starting point is a main contingency plan checklist that includes the following sections: scope, policy and legislation, roles and responsibilities, anticipation and assessment, preparation, detection and reporting, response, cost and equipment, risks, communication, documentation, and evaluation and revision. This base document can be supplemented with information annexes per taxonomic group or species, depending on the scope of the plan. By providing a standardised framework, these guidelines bridge the gap between theoretical preparedness and actual response. This approach enables authorities to develop comprehensive contingency plans, regardless of the species or geographic region, and reduces the risk of administrative and organisational delays following detection. Ultimately, this guidance serves as an important asset in harmonising international efforts to mitigate incursions of invasive, alien species through organised and effective action.

Abstract Biological invasions are a major driver of global change, reshaping ecosystems and threatening biodiversity worldwide. Anticipating where invaders will establish and where they will exert the strongest ecological impacts are key challenges for early detection and targeted management. Although Species Distribution Models (SDMs) are widely used to forecast biological invasions, they often provide uncertain estimates of establishment ranges and limited insight into invader performance, making it difficult to anticipate ecological impacts. Here, we address these limitations by integrating physiological information on invader performance with SDMs to identify regions of high invasion risk. Using the brown alga Rugulopteryx okamurae, one of the most prominent marine invaders in Europe, we first test alternative hypotheses of northern establishment limits: (i) a cold-survival constraint driven by winter temperatures and (ii) a growth constraint derived from the species’ thermal performance. To identify the more likely scenario, we combine cold-tolerance experiments with seasonal growth comparisons between the invader and a native macroalga Dictyota dichotoma , whose established distribution allows physiological performance to be directly related to realised presence. Finally, we project seasonal growth of the invader across the predicted establishment range as a proxy for biomass accumulation and potential ecological impacts. Our results indicate that northern limit in Europe will be more likely constrained by winter survival rather than growth, extending the potential establishment range of Rugulopteryx to mid-Norway. In contrast, the highest impacts are likely to remain concentrated in southern Europe, where thermal conditions sustain high year-round growth. Overall, our approach illustrates how understanding the physiological response of invaders to their environment can improve the interpretation of SDM outputs and help identify areas at greatest risk of impact within their potential establishment range.

Ring-necked parakeets (Psittacula krameri) are among the most successful avian invaders in Europe. Since their establishment in the 1970s, populations have expanded across the continent, with urban areas serving as primary strongholds. Despite growing concern over their ecological impacts, including competition with native cavity-nesting species and agricultural damage, fine-scale information on how breeding individuals use urban landscapes remains limited. Understanding space use and habitat selection during the breeding season is essential for predicting further range expansion and informing management strategies. Here, we present the preliminary results of an ongoing GPS telemetry study investigating the spatial ecology of breeding ring-necked parakeets in the city of Antwerp, Belgium. Individual parakeets were captured at breeding sites using mist nets deployed near active nest cavities. Birds were fitted with lightweight solar-powered GPS transmitters (~5 g) attached via Teflon harnesses. Tags were programmed to record locations throughout the breeding period (April–June), which mainly corresponds to the chick-rearing period. Concurrent with the telemetry work, we conduct standardized field observations at sites identified from GPS fixes and at matched comparison sites across the urban landscape. At each site, we record resource availability through systematic surveys of the nearest trees and their phenological state, and collect focal behavioral observations of foraging parakeets. This links individual movement patterns to fine-scale habitat characteristics and food resource availability. Our analysis characterizes the relationship between urbanization gradients and space use, specifically determining the extent to which home range size and foraging selectivity vary across different habitat configurations. We examine how the concentration of food resources influences the trade-off between commute distances and quality of foraging sites.

Worldwide, illegal wildlife killings and habitat destruction cause ecological damage, leading to substantial losses in biodiversity and ecosystem services, impacting both nature and people. Legal regulations mandate the restoration of damaged nature, yet restoration “in natura” is often impossible and determining fair compensation in court remains challenging due to a lack of standardized valuation methods for species and habitats, as well as clear and transparent guidelines for their application. This paper presents a research process where judges, legal experts, and ecologists collaborated to develop a practical and transparent method for calculating indicative financial compensation amounts for damage to vertebrate species, which was piloted in Flanders, Belgium. Our approach integrates the IPBES assessment on diverse values and valuation of nature, moving beyond purely instrumental or intrinsic values to encompass plural values that reflect the complex relationships between nature and people. The resulting “BIOVAL” method and indicative list of compensations provide a robust, science-based instrument for court rulings, helping to bridge the expertise gap faced by judges and enabling more efficient and equitable compensation claims. Developed through co-creative workshops with legal professionals, the BIOVAL method balances conceptual rigor with real-world applicability, aiming to ensure legitimacy and acceptance within the legal system. This innovative approach offers a replicable template for constructing compensation lists in other jurisdictions, promoting justice and ecosystem conservation based on recognition of the plural values of nature.

Ticks play a significant role in the transmission of various pathogens, impacting both human and animal health. Understanding the factors influencing tick feeding preferences is crucial for mitigating the risk of tick-borne diseases. This study investigates the blood preference of Ixodes ricinus nymphs, focusing on host species, stress hormone levels (glucocorticoids), and the presence of Borrelia burgdorferi s.l. bacteria. We conducted three series of in vitro experiments using a setup where individual blood drops (15 μl) were placed on filter paper over a 37 °C plate. Ticks were placed in the center, and their movements were tracked for 2 min to record preferences. The first experiment tested preferences for blood from different hosts (mouse, bird, sheep). The second examined the role of stress hormones by offering blood with varying levels of added cortisol and corticosterone (0, 10, 100, 1000 ng/ml). The third experiment investigated the potential influence of Borrelia infection, combined with elevated stress hormone levels, on blood preference. Our results show that I. ricinus nymphs preferred blood without added glucocorticoids and, in mice, blood with Borrelia infection. No clear preference for a specific host species was observed. These findings offer insights into how host physiological state may affect tick host selection, even though I. ricinus may not always have the opportunity to choose between hosts. Future studies should explore these interactions in more biologically relevant models to better understand the dynamics of tick attachment and feeding. Unraveling these mechanisms could aid in developing new strategies to control tick-borne diseases.

The Anthropocene is characterised by a continuous human-mediated reshuffling of the distributions of species globally. Both intentional and unintentional introductions have resulted in numerous species being translocated beyond their native ranges, often leading to their establishment and subsequent spread - a process referred to as biological invasion. Biological invasions are associated with profound changes in the composition, structure, and functioning of recipient ecosystems, plus substantial financial losses and disruptions to society, culture, and human well-being. These ecological, economic, and socio-cultural impacts are interrelated, ubiquitous, and detrimental, yet they are often subjectively perceived or inaccurately quantified. Persistent knowledge gaps remain, however, which limit our understanding of the complex and multifaceted causes and mechanisms of invasion impacts. To overcome these gaps and comprehensively capture all related facets pertaining to the nature and diversity of invasion impact, this scoping review of academic studies, grey literature, and expert reports provides a conceptual model for interpreting invasion impacts, structured around three interrelated pillars: impact domains, challenges in the study of impacts, and available risk- and impact assessments. We initially explore the various mechanisms and consequences of ecological, economic, and socio-cultural invasion impacts and their temporal dynamics, substantiating these with relevant empirical examples. We then review common challenges and fallacies in studying invasion impacts, including context specificity and inter-comparability of impact magnitudes, challenges associated with quantifying non-ecological impacts, and research biases, before synthesising how risks are analysed and impacts assessed, and how these assessments ultimately inform management decisions. Our review underscores the multifaceted and complex nature of invasion impacts, and that effectively addressing biological invasions requires more than isolated, reactive interventions; it calls for globally coordinated, proactive action underpinned by reliable scientific knowledge, sincere political commitment, and broad public engagement. Drawing on nearly a century of literature and global expert contributions, this work offers a comprehensive, nuanced, and timely overview of the potential consequences of biological invasions, providing a valuable foundation for informing future research directions, management interventions, and policy development.

Forests provide crucial habitats for nature and people, but also harbour organisms, such as ticks, that can act as vectors for pathogens. Understanding how forest management practices influence host-parasite-pathogen interactions is essential for promoting both forest biodiversity conservation and nature's contributions to people. This study investigates the complex relationships between forest structural complexity, body condition, and tick infestation probability in a common forest bird, the great tit (Parus major), across 19 forests in the Flemish Ardennes, Belgium. Using Structural Equation Modeling (SEM), we first integrated multiple phenotypic health proxies into a single overall condition index. Subsequently, we assessed how variations in forest structural complexity impact the condition of forest birds and their chances of contracting ticks. Our findings showed that birds in better physiological condition, as indicated by lower levels of cellular stress, were more likely to carry ticks. This may be due to ticks preferring healthier and more nutritious hosts and/or condition-linked differences in bird behaviour (e.g. foraging), resulting in higher contact rates with ticks. While forest structural complexity did not significantly affect the birds' overall body condition, it was responsible for an increased tick infestation probability. Specifically, forests with higher structural complexity were associated with increased densities of questing nymphs, thereby elevating the risk of tick infestation in birds. This study highlights the multifaceted role of forest structural complexity in shaping host-parasite dynamics. These insights are valuable for developing forest policies that balance the enhancement of ecological health with the mitigation of health risks posed by tick-borne diseases.

Forest structural complexity influences arthropod communities by shaping habitat availability, microclimatic conditions, and resource distribution. However, the extent to which structural complexity and specific structural components drive arthropod abundance and biomass remains poorly understood in temperate forests. This study examined how local and landscape-scale forest characteristics influence arthropod communities across vertical strata (forest floor (FF), herb layer (HL), and shrub layer (SL)) in 19 temperate deciduous forests in Belgium, dominated by pedunculate oak, European beech, or Canadian poplar. At the local scale, we assessed dominant tree species identity, overall forest structural complexity, and its components (vertical and horizontal structure, woody layer, herbal layer, and deadwood). At the landscape scale, we evaluated forest area, edge length, forest cover, and vegetation greenness (normalized difference vegetation index (NDVI)). Contrary to expectation, arthropod biomass and abundance did not consistently increase with higher structural complexity. Instead, woody layer complexity, dominant tree species, and NDVI emerged as key drivers, with effects varying by context and stratum. Arthropod abundance and biomass were the highest in oak- and poplar-dominated forests and the lowest in beech forests, likely due to differences in litter quality, microhabitat availability, and understory development. Woody layer complexity positively influenced forest floor arthropods in poplar forests but had a negative effect in oak forests. At the landscape scale, NDVI unexpectedly showed negative relationships with arthropod abundance across strata and with arthropod biomass in the herb layer, likely reflecting dense canopy suppression of understory productivity. Arthropod biomass on the forest floor increased with forest cover, while abundance in the shrub layer decreased with forest cover but increased with forest area. These findings highlight the complex interplay between forest structural attributes, dominant tree species, and landscape factors in shaping arthropod communities. By identifying the key drivers of arthropod abundance and biomass, this study contributes to a better understanding of biodiversity patterns in temperate forests and their ecological dynamics.

This study examines the ecophysiological responses of common waxbills to temperature variation in Portugal. We measured body condition and basal metabolic rate (BMR) during summer and winter across two regions in Portugal. Body condition was negatively correlated with temperature, while the relationship between BMR and temperature varied seasonally. In summer, BMR decreased with increasing temperature, but in winter, it remained low and stable, indicating physiological adjustments to seasonal changes.

Scientific meetings, conferences and publications are crucial for advancing knowledge and collaboration, but geopolitical tensions and territorial disputes can hinder the free exchange of ideas, especially when presented maps depict contested borders. These challenges threaten the integrity of scientific discourse and can cause discomfort among researchers. To address this, we recommend guidelines for event organizers, researchers and publishers to minimize geopolitical sensitivities, by omitting borders when unnecessary, relying on natural features like mountain ranges, watersheds or climatic regions, and using the United Nations geoscheme. By fostering open dialogue and adhering to international standards, these measures can help protect scientific independence, promote unbiased communication, and maintain focus on research in politically sensitive contexts.

Research exists to make an impact. It is not necessarily aimed at profit, but seeks to meet societal, environmental and/or cultural needs, while also generating and sharing new knowledge. Sometimes this knowledge has a direct application; other times, it serves curiosity. This blend gives research its vitality. Yet research is typically packaged into short-lived projects. They begin with a question or funding call and end when resources run out. The tension is clear: the specific questions may be time-bound, but the value of the knowledge, data and tools is not. Too often, outputs lose visibility and become hard to reuse. There is also a tension between internal project coherence and broader alignment with institutional strategies, collaborators and policy frameworks. Trade-offs are inevitable between speed and sustainability, innovation and standardisation, and serving current needs versus preparing for future ones. This interplay between the ephemeral and the enduring is central to the sustainability and value of research. Our reflections draw on several recent projects. The Belgian TrIAS project (2017–2021) built open data pipelines for science and policy and designed its workflows with reuse in mind. These were not one-off solutions but adaptable foundations. Later projects such as B-Cubed (2023–2026), LIFE RIPARIAS (2021–2026), GuardIAS (2025–2027) and OneSTOP (2025–2028) build on this base (Katsanevakis 2024, Groom 2025). While their objectives differ, all shared a concern for durability. They reuse methods, extend infrastructures, and align with open standards. Durability is never accidental. It requires researchers to consider sustainability from the outset. Datasets are published under CC0, software under open-source licenses, and publications under CC-BY. To endure, research outputs must be embedded in open, stable and widely used infrastructures, such as GBIF, Zenodo, GitHub, Wikidata. These platforms increase visibility and allow others to build upon prior work. Standards are equally essential. The frameworks developed by Biodiversity Information Standards (TDWG) and others enable interoperability, so data from different sources can be combined, compared and reused (Hardisty and Roberts 2013). We’ve learned to design workflows for reuse. For example, the WiSDM species distribution modelling workflow developed in TrIAS has been picked up in OneSTOP and GuardIAS (Davis et al. 2024). This reuse saves effort but also builds continuity as each project leaves a trail others can follow. Furthermore, when tools are co-developed, they are more likely to be maintained and adapted. Communities of practice allow knowledge and lessons to flow from one project into the next. Some of the most lasting outcomes of research are the relationships it creates. Durability requires deliberate choices. Openness, interoperability and relevance ensure that research lives beyond its funding cycle. Aligning with standards, designing for reuse, and investing in shared infrastructure all help secure this. Communication is part of this, including clear documentation, identifiers, and presentation or contextualization that make outputs understandable and trustworthy. The real lesson is that long-term impact doesn’t come from isolated brilliance, but from embedded, reusable, shareable work. Funders, institutions and researchers all have a role to play in making this shift, and if we succeed, even short projects can leave lasting legacies.

Long-distance endurance flight in migratory birds requires numerous physiological adaptations. Maintaining the necessary physiological machinery may require increased energy expenditure, which could manifest as an elevated basal metabolic rate (BMR). Comparing the BMR of long-distance migrants and residents using global BMR datasets is complicated by the fact that data for migrants typically come from higher latitudes and colder regions than those for nonmigrants. Separating the effects of ambient temperature (Ta) and migratory tendency on BMR is challenging because of the well-documented high phenotypic plasticity of avian BMR, which is reflected in the negative relationship between BMR and Ta. We hypothesized that tropical migrants would have a higher BMR than residents because of the cost of maintaining a more enduring and/or flexible physiology. Additionally, according to the climatic variability hypothesis (CVH), BMR plasticity should be greater in regions with more variable climates. To test these hypotheses, we measured BMR in 130 sedentary species and 25 migratory species from two remote areas in Vietnam that differ in climate. As expected, we found that in both sites, migrants on their wintering grounds maintained a higher mass-independent BMR compared with tropical residents. Moreover, the BMR of wintering migrants was not lower than their BMR on their breeding grounds. Sedentary species inhabiting a milder and more stable climate had lower BMR than those in colder and more variable environments. The individual long-term repeatability of BMR in the milder climate was higher than that in the area with a more variable climate, which is consistent with the CVH.

Nature-based solutions (NbS) are emerging as promising strategies for addressing societal and environmental challenges, striving to transform cities into more resilient and sustainable environments. NbS harness nature and ecological processes to provide multiple benefits and while supporting biodiversity. Although urban greening is widely promoted through NbS, evidence on their effectiveness in supporting biodiversity remains limited. A key challenge is determining optimal implementation levels to maximize biodiversity gains, as most studies simply compare presence versus absence of NbS. To address this gap, we conducted a metropolitan-scale survey of over 1, 000 sites across four NbS types-street trees, urban green spaces, green roofs, and water sites-analyzing dose-response relationships between natural elements and urban bird diversity. Our findings reveal predominantly non-linear biodiversity responses, suggesting that 'more is not always better' and that effectiveness depends on ecological context. Tree cover, vegetation complexity, and bank vegetation emerged as key positive drivers of bird diversity, yet their benefits often peaked at intermediate levels. Street trees supported bird diversity up to ∼30 % cover, after which increases were marginal. In green spaces, species richness was highest at moderate levels of tree and shrub cover, emphasizing the importance of structural heterogeneity. Water sites with naturalized banks had significantly higher bird diversity than artificial water bodies, while green roofs contributed minimally to avian biodiversity. Altogether, these results demonstrate that NbS must explicitly integrate biodiversity objectives. Maximizing biodiversity benefits requires developing and implementing NbS designs that account for non-linear biodiversity responses and biodiversity thresholds, and consider the regional ecological context.

More and more forest management focuses on increasing structural complexity to improve environmental conditions for biodiversity and forest functioning. However, it remains uncertain whether animal populations also benefit from increased forest structure. Small mammals are key reservoirs for zoonotic diseases, so understanding how forest structure changes their condition and how this, in turn, affects infection dynamics is critical for animal and human health. This study examined relationships between forest structural complexity, individual body condition (scaled mass index (SMI) and telomere length), pathogen prevalence, and tick load in bank voles and wood mice across 19 forest plots in northern Belgium, representing a gradient of structural complexity. Results showed that higher forest complexity, especially with more dead wood and a well-developed herb layer, increased small mammal abundance. Density varied by tree species, with highest abundances in oak and lowest in poplar forests. In addition, body condition improved with structural complexity; SMI increased with woody layer complexity in wood mice and with dead wood availability in bank voles. No clear relationship between telomere length and forest complexity was observed. The relationship between body condition and pathogen prevalence was species- and pathogen-specific. Small mammals in better body condition were more likely to host Borrelia burgdorferi (causing Lyme disease), particularly in complex forests, indicating a higher infection risk with increasing structural complexity. Forest management practices that aim to enhance forest structure and biodiversity may thus inadvertently increase zoonotic disease risk and should take these findings in consideration to minimize the risk for human health.

Biological invasions and climate change are two of the most pressing drivers of biodiversity loss worldwide. Anticipating where invasive species are likely to establish, as well as the potential impact of climate change on their range expansion, is essential for early detection and targeted management. In this study, we use a mechanistic species distribution model (SDM) to evaluate the current and future areas at risk of invasion by the common waxbill ( Estrilda astrild ), a widespread avian invader. Our model accurately predicts the species’ current range in Iberia and identifies additional climatically suitable areas, particularly in southern and western Europe. Under warming scenarios of +2 °C and +4 °C, suitable areas expand northwards, with over two-thirds of Europe classified as suitable under the most extreme scenario. These results suggest that the species is already operating near the cold limits of its thermal niche in parts of its invasive range, and that rising temperatures may remove these constraints, allowing expansion into previously unsuitable areas. Our findings demonstrate the power of mechanistic models in identifying regions at risk of colonisation and underscore the importance of early intervention and targeted monitoring in areas projected to become suitable. ### Competing Interest Statement The authors have declared no competing interest.