Land-use change and climate change are reshaping ecosystems across Europe, where traditional low-intensity land-use practices once maintained open habitats rich in biodiversity. Specialist species, such as the Apollo butterfly (Parnassius apollo), which depends on semi-open, sunny habitats with its larval host plant, orpine (Hylotelephium telephium), and nearby nectar plants, are especially vulnerable. In Finland, the Apollo butterfly has declined severely, yet its outer archipelago population have long been considered a national stronghold for the species. This thesis combines the use of long-term monitoring, habitat analyses, restoration experiments, and social surveys to assess ecological and social dimensions of Apollo conservation in the southwest Finnish archipelago.

First, I compared historical survey data (1997, 1999–2003) with recent data (2019–2020) to quantify possible changes in the Apollo butterfly occupancy and host plant abundance. Occupancy declined from ~75% of islands to ~20%, despite stable host plant abundance, suggesting that other factors, such as habitat quality and demographic constraints, now play stronger roles in shaping the butterfly’s persistence than host plant abundance alone. Second, I surveyed 327 rocky outcrops in the coastal population. Occupancy was linked to host plant abundance, lower tree volume, higher elevation, and proximity to nectar patches, but not patch size or connectivity, showing that in dense habitat networks, habitat quality currently outweighs spatial configuration. Third, I evaluated restoration outcomes on 49 islands where junipers were cleared and burned. Occupancy continued to decline even after management. The population may have declined too much for habitat improvements to lead to colonisation in the short term. Vegetation, however, responded quickly: restored sites gained plant species richness, shifted toward nectar-rich communities, and showed higher functional diversity, thereby presumably supporting butterflies and other insects. The results indicate a lag between vegetation recovery and the butterfly response. Finally, a survey of 230 residents, visitors, and landowners in SW Finland showed that pro-environmental values predicted support for ecological management. However, support was weaker for local interventions such as juniper removal or conservation of the Apollo butterfly.

Together, these results show that Apollo conservation requires maintaining critical resources, open habitats, and stakeholder engagement. This thesis integrates ecological monitoring, restoration, and social acceptance, offering a holistic perspective on conserving an emblematic butterfly in a changing archipelago.