# Habitat Loss and Other Threats to the Survival of _Parnasius apollo_ ([PERSON], 1758) in Serbia
## 4 Discussion
Our findings confirm that the presence of _Parnassius apollo_ at the studied sites is not determined by elevation per se [4], but rather by habitat structure and microclimatic conditions. The species inhabits dry, rocky limestone habitats well below the alpine zone, consistent with its ecological preferences in other parts of its range [68; 70]. This supports the view that conservation efforts should prioritize the preservation of open habitats maintained by traditional land-use practices [104], rather than relying solely on altitudinal classification. While often considered endangered in Western Europe, _P. apollo_ remains locally abundant in parts of Eastern Europe and Central Asia, suggesting that Western populations represent subperipheral, fragmented remnants of a much broader distribution range [105]. In addition to succession and thermal stress, metal contamination represents a significant threat. Historical research in Finland linked atmospheric deposition of metal dust from mining to the decline of _P. apollo_, with population recovery following emission reductions [26]. A similar pattern is observed in Serbia: elevated metal loads were detected near mining-affected regions such as Mount Stol and Kopaonik, where butterfly populations are absent, further supporting the role of environmental contamination in population collapse. One of the most acute disturbances documented is the wildfire that occurred on Mount Stol in August 2024. Post-fire assessments using spectral indices (BAI, NBR, NBR2) revealed extensive vegetation loss and spatial heterogeneity in burn severity. While wildfires are ecologically natural in many systems, in already degraded landscapes they act as amplifiers of succession and habitat instability [70]. In the absence of grazing, burned areas are rapidly colonized by aggressive shrubs, locking habitats into late-successful states unsuitable for _P. apollo_[67; 70]. This study underscores the combined influence of multiple biotic and abiotic drivers in shaping the extinction trajectory of _P. apollo_. While each mechanism was assessed individually (e.g., grazing abandonment, climate stress, mining pollution, fire disturbance), their ecological effects were interpreted cumulatively based on spatial and temporal overlap observed in the field and supported by remote sensing and site-specific data. Although formal statistical interaction terms were not included in this study, the co-occurrence of multiple stressors at critical sites suggests additive/synergistic effects on habitat degradation. For instance, climate warming not only imposes physiological stress but also intensifies the effects of drought, shrub encroachment, and fire susceptibility. These combined pressures are more likely to trigger local extinctions than any single factor alone. The findings therefore support a multifactorial framework in interpreting insect decline and stress the importance of integrating multiple causal dimensions in conservation planning [58; 61; 62]. Effective conservation must therefore adopt an integrated approach. Reintroduction programs, as demonstrated in Pieningy National Park, have shown limited success when conducted in isolation from habitat restoration [52; 63]. Traditional pastoralism, once perceived as outdated, now emerges as an essential ecosystem service. Without reestablishing extensive grazing and managing vegetation succession, even remaining Serbian populations are at imminent risk of extinction within the next decade. Although this study focused on _P. apollo_, several other butterfly species, such as _Scolitantides orion_, also depend on open, seric habitats and similar larval host plants [106]. During the course of fieldwork, _S. orion_ was recorded in considerable numbers at Site 1, indicating the presence of a stable and locally well-established population. The species was frequently observed in habitats dominated by _Sedum album_, which serves as its primary larval host plant. Monitoring the responses of _S.