Vetnews | Maart 2026 12 « BACK TO CONTENTS In a landscape-scale conservation strategy using multiple small reserves, two critical factors come into play: the adaptive capacity of pathogens and the connectivity between patches [36,37]. It is worth pointing out that pathogen adaptation is always challenging to forecast and can take many different forms. Nevertheless, the likelihood of pathogen adaptation (i.e., increased transmission in this case) is linked to its adaptation potential, which is the quantity that could be directly measured (e.g., pathogen mutation rate, pathogen substitution rate, etc.). When inter-patch connectivity is low, patch sizes are reasonable, and pathogens adapt quickly to their environment, this approach can foster local pathogens’ adaptation. In other words, each patch would host its own strain (i.e., a genotype), leading to low pathogen diversity at the patch level but high diversity across the entire region. Pathogen transmission would likely be high within individual patches, but low between them [38,39]. While the pathogen hazard remains high due to its wide geographical distribution, the risk of widespread transmission would be more contained. On the other hand, if a pathogen adapts more slowly to its environment, we would expect a mosaic of ‘hot’ and ‘cold’ spots of adaptation [40]. In hotspots—where pathogens are well adapted— transmission would be high. But in cold spots, where environmental changes outpace pathogen adaptation, transmission would be low, possibly even leading to local pathogen extinction. Compared to fast-adapting pathogens, this scenario would see a decrease in overall transmission and pathogen diversity at the landscape level. As a result, both the hazard and the risk of the remaining pathogens would likely be lower. These impacts can be significantly influenced by increasing patch connectivity. When patches are fully connected, the dynamics resemble those of a single large population, where high pathogen adaptation and transmission are favoured—though predicting exact outcomes becomes more challenging (see Table 1). On the other hand, with low or intermediate connectivity, pathogens may struggle to adapt due to conflicting pressures between local and regional environments [38]. This tension limits a pathogen’s ability to thrive in both contexts, potentially resulting in a global reduction in both hazard and risk. However, if connectivity becomes too strong, it can create a complex mosaic of adaptive responses, especially under high genetic drift, making patterns of pathogen adaptation difficult to predict. To leverage this type of conservation strategy for reducing pathogen transmission, it is essential to strike the right balance— determining the ideal patch size and connectivity level to maintain this local-regional adaptation conflict. Doing so could help minimise transmission levels [22] and offer a clear benefit in terms of the hazard-risk trade-off. Such a threshold, when identified, can become a key tool to develop win-win strategies between biodiversity protection and human health. This approach contrasts with the design of traditional large reserves, which are often based on specific conservation needs, such as protecting biodiversity hotspots or preventing areasensitive species loss. While large reserves may offer ecological benefits, they often result in high species and pathogen richness, making their impact on pathogen circulation harder to predict. These areas might target Key Biodiversity Areas (KBAs), but due to the diversity of host communities within and between KBAs, the effects on pathogen dynamics remain uncertain. Some conservation strategies focus on specific species, like keystone species, to maintain high species richness. In these cases, the outcome for pathogen transmission depends heavily on the makeup of surrounding animal communities— particularly the ratio of competent versus non-competent species in the ecosystem. Similarly, focusing on flagship species may boost conservation efforts but have little impact on pathogen dynamics unless that species plays a pivotal ecological role. Translocation strategies are also unlikely to affect pathogen transmission unless they significantly alter the structure of animal communities. In summary, developing large reserves to mitigate zoonotic risks may produce highly variable results, making it a less reliable option for protecting human health from zoonoses. Figure 1. Examples of dilution and amplification effect. The competence (number of circles) and abundance (number of individuals per species) within animal communities, and their influence on pathogen transmission. Both ecosystems show a perfect positive (Ecosystem A), null (Ecosystem B) and negative (Ecosystem C) correlation between competence and abundance of each species (species 1 to 9). A dilution effect is expected in Ecosystem A, an amplification effect in Ecosystem C, while no impact on pathogen transmission is expected in Ecosystem B. Leading Article Leveraging Small Biodiversity Reserves to Prevent..... <<< 11
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