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.