Protected areas (PAs) are a core strategy for meeting the global 30×30 conservation target of protecting 30% of lands and waters by 2030. Yet expanding PA coverage alone will not secure biodiversity if these areas remain isolated. Given that most species often require movement among habitat patches, ensuring connectivity across landscapes is therefore essential for PAs to function as an effective ecological network rather than as isolated units.
PAs differ widely in their level of legal protection, management goals, and allowable human activities. Strict PAs aim to conserve biodiversity with minimal disturbance, but they are typically limited in extent.
Prima, M.C., Oliveira‐Cruz, L., Miele, V., Si‐Moussi, S., Rouveyrol, P., Suarez, L. and Thuiller, W. 2025. Multilayer network analysis reveals connectivity synergies between protected area levels across various taxonomic groups. Conservation Letters 18(5): e13148. DOI: 10.1111/conl.13148.
In contrast, non-strict PAs cover much larger regions and can facilitate movement, yet they permit more human use and may offer lower habitat quality. A key question for conservation planning is whether these different protection levels can complement each other and collectively enhance functional connectivity for a wide range of species.
A recent study addressed this question by assessing connectivity across metropolitan France for 397 species of vertebrates, invertebrates, and plants. The authors used species distribution models to map suitable habitat, then applied the Omniscape algorithm to model ecological continuities that represent potential movement pathways. Species were grouped based on shared ecological traits, habitat needs, and dispersal capacities.
The researchers then constructed spatial networks linking PAs that were both within ecological continuities and located within species specific dispersal distances. Separate networks were built for strict PAs alone, non-strict PAs alone, and a combined multilayer network that integrated both.
The results showed that non-strict PAs, including regional natural parks and Natura 2000 sites, provided the majority of connectivity because they are more numerous and cover a much larger area than strict PAs. However, strict PAs still played an important role when considered within the multilayer network. The combined network revealed a strong synergy in which non-strict PAs facilitated access to high quality habitat within strict areas.
This effect was particularly notable for mammals and birds, which showed higher connectivity across protection types. Connectivity for insects, amphibians, reptiles, and plants remained comparatively limited, largely due to shorter dispersal distances or narrower habitat requirements.
These findings reinforce the need to view PAs as interconnected components of a broader conservation landscape. Achieving 30×30 targets without attention to connectivity will fail to support long term species persistence, especially under accelerating climate and land use change. Conservation strategies should integrate strict and non-strict PAs with corridor design, restoration, and land management practices that increase matrix permeability.
More broadly, the study demonstrates the value of multilayer network analysis for evaluating how different categories of PAs interact. This approach provides actionable insight for designing protected area networks that are cohesive, resilient, and capable of sustaining biodiversity into the future.
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