Forests are dynamic ecosystems that are constantly exposed to various disturbances, both natural, such as insect pests, fires and drought, and anthropogenic. A key characteristic that determines their ability to survive and recover from these events, is biodiversityThe diversity of life in a forest ecosystem, i.e. biodiversity, fundamentally influences the resilience of forests and their ability to adapt to changing conditions.

Why is biodiversity key to forest resilience?

Biodiversity plays an irreplaceable role in forest resilience and is one of the most difficult ecosystem services to replace.

• Reduces the risk of widespread die-offs: Forests with higher species and functional diversity are less prone to widespread tree dieback. Different tree species respond differently to stress and disturbance, and this effect is more pronounced when species with different characteristics are mixed, such as slow- and fast-growing trees.
• Stabilizes productivity: Higher tree diversity can increase the security and stability of forest production, making it a strategic asset for timber-based forestry. Although productivity may decrease with a higher proportion of slow-growing species, overall stability increases.
• Supports adaptive capacity: Biodiversity is highly valued and supports the adaptive capacity of forests, ensuring the resilience of ecosystems and society as a whole.

The impact of disturbances on biodiversity and possibilities for its enhancement

Increasing natural disturbances, such as insect pests and fires, often make forests younger and more open. This process benefits species that need light to grow, but harms those that depend on old and dense forests. Interestingly, natural disturbances can also enhance biodiversity, as they create opportunities for the introduction of (more) climate-adapted tree species.

What can policymakers and forest managers do to strengthen forest biodiversity and resilience?

Improving forest resilience through biodiversity requires a coordinated approach that includes:

1. Increasing species diversity of woody plants:
   • Supporting a mix of tree species with different functional properties (e.g. deciduous and coniferous species with different drought tolerance and sensitivity to disturbance) to improve recovery from disturbance and adaptation to climate change.
   • Diversification of tree species composition to reduce the risk of widespread losses during extreme weather events.
   • Linking ungulate grazing management with increasing tree diversity.
   • Creating forests with a mix of tree types and structures that support different species to maintain both biodiversity and timber production.
2. Promoting structural diversity:
   • Supporting the development of uneven-aged forests to reduce vulnerability and accelerate recovery from disturbances.
   • Support for leaving dead wood in the forest to increase biodiversity and the water and nutrient cycle.
   • Motivation for advanced natural recovery in forest stands to accelerate recovery after disturbance.
3. Using Disturbances to Enhance Biodiversity:
   • Preserving the heritage of disruptive influences, such as deadwood, advanced regeneration and surviving trees, to support forest regeneration, biodiversity and the provision of habitat for wildlife.
   • Using new cultivation approaches, which mimic the dynamics of disturbances.
4. Re-evaluation of management measures:
   • Usage locally adapted forestry practices.
   • Designation of rest areas with the potential to increase their conservation value over time, serving as "biodiversity islands" in the landscape.
   • Managing game density to support the natural regeneration of species adapted to the site.
5. Financial support and training:
   • Implementation of training programshow to manage forests in ways that benefit biodiversity and increase resilience.
   • Offering financial incentives to support tree species diversity and functional diversity, as well as various aspects of structural complexity.

Trade-offs and the importance of local context

Although increasing biodiversity is key, it is important to be aware of certain trade-offs. Increasing tree species diversity can reduce short-term economic profits from wood production, but at the same time builds long-term stability and resilience of the ecosystem. Intensive management practices can mitigate some of the impacts of disturbances, but they often harm biodiversity and forest multifunctionality. Also, the legacy of disturbances such as dead wood, while beneficial to biodiversity, can increase risks, such as pests or fires.

The regional and local context is extremely important.

Local conditions must determine which measures (e.g. species selection, disturbance prevention) are feasible and effective, as uniform strategies increase the risk of failure. Zoning the landscape can help balance priorities and achieve optimal results.

Biodiversity is an integral part of forests' resilience to disturbances and key to their long-term sustainability. Investing in forest biodiversity is not only an environmental goal, but also a strategic step towards ensuring stable and productive forest ecosystems for future generations. Spring

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