Not just dead wood: Why forests need their old and decaying trees

Daria Kononenko on 22 May, 2025

If we ask you to think of a healthy forest, you might picture tall, straight trees, green canopies, and neat trails. But some of the most valuable parts of a forest aren’t so perfect – they’re cracked, hollow, decaying, and lying scattered on the ground. These are deadwood and habitat trees – and they’re biodiversity hotspots, providing shelter and food for a wide variety of species that are essential to forest health. 

Habitat trees and dead wood offer a large variety of microhabitats supporting biodiversity, and may be threatened by harvesting in managed forests (inspired by Bütler et al. 2020, Humphrey and Bailey 2012). Source: Muys, B. et al. (2022), Forest Biodiversity in Europe, From Science to Policy 13, European Forest Institute, p.34. https://doi.org/10.36333/fs13

Why standing snags and fallen logs matter for ecosystems 

Deadwood is far from lifeless. Insects, fungi, mosses, lichens, birds, bats, and small mammals all depend on them at different stages of decay. Some beetle species lay their eggs only in old rotting logs. Mosses and lichens often grow on declining trees and shrubs, as well as on stumps and snags. Deadwood provides a nutrient-rich surface that supports their growth over time. 

Fungi are uniquely capable of breaking down lignin – the tough material that gives wood its strength and rigidity. In doing so, they unlock and return long-stored nutrients from the tree back into the soil.  

Habitat trees are living or dead standing trees that offer similar benefits. Often old and marked by natural damage, they may have dead branches for some birds to roost and watch for prey, peeling bark, or cavities, where woodpeckers and owls nest. Cracks, crevices, and notches also create vital microhabitats – this is where many other species find shelter, breed, or escape predators. Across the seasons, habitat trees offer plenty to eat – nectar, pollen, fruits, seeds, leaves, and even wood and leaf litter.  

How TRANSFORMIT is making space for life 

Dead and damaged trees have long been treated as waste – something to be cleared away. But in many managed forests, especially those with short rotation cycles, deadwood and habitat trees are already in short supply. Yet these natural elements are vital for biodiversity, providing food, shelter, and breeding grounds for countless species. This makes their integration a crucial part of sustainable forest management. 

With the TRANSFORMIT project, we’re putting this into practice. Here’s how: 

  • In our Living Labs, serving as real-world examples of integrative forest management (IFM), we are implementing practices that balance productive forestry and biodiversity conservation 
  • Creating practical, evidence-based IFM guidelines and indicators to address multiple forest management goals – from biodiversity conservation and resilience to climate change mitigation and community benefits 
  • Showcasing innovative tools such as decision support systems, forest modelling, and interactive digital twins to help improve forest management and decision-making 
  • Running workshops, webinars, and training sessions to spread knowledge and promote IFM practices across Europe and beyond 

Dead and decaying trees aren’t forest waste – they are key to keeping forests alive, diverse, and resilient. Leaving them in the forest supports our woodlands to be home to diverse species and cope with increased disturbances, whether from climate change or human activity.