Forests are more than collections of trees – they are living systems shaped by time, disturbance, and the countless microhabitats that sustain biodiversity. A new WILDCARD study titled “Beyond management: Proforestation enriches tree-related microhabitat diversity, but forest types determine their composition across Mediterranean and Alpine forests” sheds light on how allowing forests to grow naturally over long periods can significantly enhance their ecological complexity.
The research explored the effects of proforestation – the practice of allowing existing forests to continue growing naturally with minimal or no logging and limited human intervention – across three contrasting forest categories ranging from Mediterranean oak systems to Alpine coniferous and mountainous beech forests. By comparing actively managed stands with forests abandoned for more than 20 and more than 60 years, the study examined how time since abandonment (TSA) influences the development of tree-related microhabitats (TreMs).
TreMs include small but ecologically critical features such as cavities, cracks, bark loss, dead branches, fungal conks, and insect galleries. These structures provide habitat, shelter, and feeding resources for a wide variety of organisms including birds, bats, insects, fungi, and plants. As indicators of forest structural complexity, TreMs are increasingly used in biodiversity monitoring and forest conservation planning across Europe.
The results of the study revealed a clear pattern: in most forest types, longer periods without management promoted greater richness and abundance of TreMs. The strongest effects were observed in Alpine coniferous forests and mountainous beech forests, where unmanaged stands accumulated more deadwood and supported a broader diversity of microhabitats linked to ageing and natural decay processes.
Results of TSA effects on TreM indices across three forest categories:
However, the study also demonstrated that there is no universal trajectory of forest recovery. Mediterranean thermophilous deciduous forests (forests found in relatively warm Mediterranean climates that are dominated by trees which lose their leaves seasonally) showed a weaker response to abandonment, suggesting that structural ageing processes occur more slowly in these systems. The researchers propose that oak-dominated Mediterranean forests may require much longer timeframes – potentially over 90 years without management – before strong old-growth characteristics fully emerge.
Importantly, the research moved beyond simply counting microhabitats. It also investigated how TreM composition changes over time. The findings showed that proforestation not only increases the number of microhabitats but gradually reshapes the entire assemblage of ecological structures present within a forest. Long-abandoned stands increasingly hosted TreMs associated with decomposition, senescence (gradual biological ageing process of an organism or its tissues), and standing deadwood, while some microhabitats linked to active forestry operations became less common.
At the same time, responses varied strongly depending on local conditions, forest history, topography, and tree species composition. Certain TreMs, such as insect galleries and exposed sapwood, increased mainly where standing dead trees accumulated, while others were more influenced by silvicultural disturbance or terrain characteristics. This highlights the importance of understanding forest dynamics within their ecological context rather than applying one-size-fits-all management assumptions.
The study offers important implications for biodiversity-oriented forest planning. As Europe seeks effective nature-based solutions for climate mitigation and ecosystem restoration, proforestation emerges as a valuable strategy not only for carbon storage but also for enhancing habitat diversity and ecological integrity. Integrating long-term unmanaged stands into forest landscapes can help create the structural conditions required by many specialised species that depend on old-growth characteristics.
Ultimately, the research reinforces a simple but powerful message: when forests are given time, they develop complexity that management alone cannot easily reproduce. Protecting existing forests and allowing natural processes to unfold may therefore play a central role in safeguarding biodiversity across both Mediterranean and Alpine ecosystems.
Reference: Marcoz, G., Tomao, A., Bitunjac, D., Boscutti, F., Duvaltier, C., Marjanović, H., Orzan, L., Piazza, N., & Alberti, G. (2026). Beyond management: Proforestation enriches tree-related microhabitat diversity, but forest types determine their composition across Mediterranean and Alpine forests. Forest Ecology and Management, 614, 10.1016/j.foreco.2026.123827
Featured image and photo by Guido Marcoz
