Designing conservation networks to ensure connectivity in a changing climate: application to Spanish forests

Aim: Assess the potential effects of climate change on different forest habitats, and outline a climate-wise conservation network to sustain forest connectivity under current and future climates.

Location: Mainland Spain.

Time period: Current and future (2071-2100).

Major taxa studied: Forest species associated with different vegetation types and dispersal abilities.

Methods: We fitted a Random Forest model to predict the distribution of six vegetation types under current and four future climate scenarios. We then assessed forest availability and connectivity for each climate scenario and vegetation type. To define the conservation network we identified the key habitat patches and corridors for dynamic connectivity using multi-temporal habitat availability indices. Finally, we analyzed how much of this conservation network is expected to change due to climate shifts and how this aligns with existing protected areas.

Results: Forests across all vegetation types exhibited substantial northward, eastward, and upward shifts. Forests adapted to cold or wet conditions (e.g., deciduous, mountain conifers, and high-mountain vegetation) declined in area and connectivity. Warm- and dry-adapted forests (e.g., sclerophyllous, subsclerophyllous, and hyperxerophilous vegetation) increased their ranges and connectivity. The increase in subsclerophyllous area tripled in connectivity gain, whereas other vegetation increased area and connectivity at similar rates (differences below 15%). 53% of the proposed conservation network shifted vegetation types. Current protected areas covered 45% of the conservation patches across Spain but less than 7% within the deciduous vegetation type.

Main conclusions: Projected shifts highlight the need for dynamic connectivity analyses to guide effective conservation under changing climates. Forest types exhibited distinct trends, underscoring the need for tailored strategies for each type. The proposed conservation network provides guidance for a proactive enhancement of forest species resilience, and serve as reference for other countries with similar conservation targets, such as the international EU Restoration Law and Biodiversity Strategy.