Forest diversification

Climate resilience Forest Diversification Pests

Our forests are dynamic and valuable ecosystems, offering a multitude of often underestimated benefits. Faced with the growing challenges of climate change, soil erosion, and biodiversity loss, forest diversification is emerging not only as a vital ecological strategy but also as a fundamental economic and social lever for our territories (MASAF, 2022). This article aims to shed light on this concept, its concrete benefits, and its challenges.

What is forest diversification?

Forest diversification goes far beyond the simple presence of several tree species. It is a global approach that seeks to increase variety at all levels of the forest ecosystem:

Species diversity : This involves planting and promoting a wide range of tree species (deciduous, conifers, native, adapted to local conditions) rather than monocultures (Leitgeb et al., 2016).
Structural diversity : This involves creating forests with trees of varied ages and sizes, different vegetation strata (trees, shrubs, herbaceous plants), and the presence of deadwood (standing and on the ground). Deadwood is part of the natural forest cycle and is crucial for conservation (WSL, 2019). For example, senescence islands in Switzerland, where trees are left until they completely decompose, aim to favor species dependent on old trees and deadwood, with a minimum presence of 50 m³/ha of standing and ground deadwood as a quality criterion (Canton de Vaud, n.d.).
Genetic diversity : Ensuring genetic richness within tree populations is crucial for their ability to adapt to future changes, particularly drought and diseases (Matras, 2013). The conservation and management of forest genetic resources are a vital component of sustainable forest management (Barbera et al., 2024).
Functional and landscape diversity : This concerns the variety of ecological roles performed by the different species and structures, as well as the richness of the forest landscapes themselves, sometimes integrating agroforestry elements (MASAF, 2022).

Why diversify ? The multiple benefits for our territories

Forest diversification provides essential ecological, economic, and social benefits, particularly for ground workers :

Strengthening resilience to climate change

Diversified forests are more stable and more resilient to disturbances (droughts, pests, diseases, fires). The Italian National Forestry Strategy aims to increase the resilience of forests to climate change (MASAF, 2022). Promoting mixed forests allows species to react in various ways to climate stress, thus increasing their resistance to climate change-related disturbances (González Díaz et al., 2020). Active forest management, focused on sustainability and climate resilience, ensures healthy and stable forests (Österreichischer Waldbericht, 2023). The Austrian forest inventory 2016/2021 confirms that the trend towards more broadleaves strengthens biodiversity and climate adaptation (Österreichischer Waldbericht, 2023).

Improvement of ecosystem services

Carbon storage and climate mitigation : The integration of complementary species in mixed forests can increase their productivity and carbon sequestration compared to monocultures (González Díaz et al., 2020). The FRL (Forest Reference Level) for Italy foresees storage of more than 19 million tons of CO2 equivalent per year (MASAF, 2022). In 2022, more than 2.85 million trees were planted in Italy, generating ecosystem services worth more than 23 million euros per year (Legambiente, 2023).
Soil protection and water regulation : Forest plantations in Spain have contributed to protection against soil erosion processes in deforested soils (González Díaz et al., 2020). In Switzerland, forests significantly reduce runoff after rainfall, thus improving water regulation (ISPRA, n.d.). Agroforestry systems also contribute to the protection of drinking water by reducing the loss of nitrates and phosphorus in groundwater (Kay et al., 2019). Forest soil is a vital habitat for many organisms and plays a key role in the water cycle (Walser et al., 2021).
Biodiversity conservation : Forest areas where any intervention is avoided favor the conservation of species dependent on old trees and deadwood (Canton de Vaud, n.d.). Forest conservation and restoration are adaptation and mitigation options identified by the IPCC (Barbera et al., 2024). Nearly 40% of species in Switzerland live in or depend on forests (Rapport forestier 2025, 2025). The creation of forest reserves, senescence islands, and habitat trees is a key measure (Canton de Vaud, n.d.; Rütler et al., 2020).

Economic and social opportunities

Valuation of forest products : It is important to value the multifunctional role of forests, including their productive use and their contribution to the circular bioeconomy (Barbera et al., 2024). The recycling of post-consumer wood in Italy, for example, makes it possible to produce panels for furniture, thus avoiding the consumption of virgin wood and reducing CO2 emissions (Barbera et al., 2024).
Agroforestry : The integration of trees into large-scale cropping systems offers benefits for biodiversity, nutrient storage, soil fixation, and the creation of new habitats for pollinators and auxiliary species (Kay et al., 2019).
Tourism and leisure : Forests contribute to public appeal and recreational and economic value (Revitalisering Nederlandse Bossen, n.d.). The increase in urban green spaces can delay the onset of health problems, particularly cardiovascular issues, by up to five years (Barbera et al., 2024).

Challenges and courses of action for ground workers

Despite these advantages, forest diversification faces several challenges, but also opportunities for direct intervention:

Fragmentation and degradation : Urban and agricultural expansion has led to deforestation and fragmentation of forest habitats (Barbera et al., 2024; WWF/Adena, 2009).
Lack of management and planning : In Italy, only 18% of the forest area is managed according to plans and the level of certification is low (MASAF, 2022). This hinders the ecological transition (Barbera et al., 2024). Forest fires, whose frequency and severity are increasing, are a major threat, often aggravated by fragmented management (Barbera et al., 2024; González Díaz et al., 2020; Grupo Siero, 2018).
Soil compaction : The use of heavy machinery can damage the structure and fertility of forest soils, as evidenced by significant increases in bulk density and reductions in porosity after the passage of vehicles (Lüscher et al., 2015). Compaction affects the structure of soil microbial communities (Frey et al., 2009, cited in Lüscher et al., 2015).

Your role is crucial to reverse these trends and promote diversification:

Soil protection during forestry work : Systematic planning of skidding trails is essential (Lüscher et al., 2015). The choice of machinery must be adapted to the soil's sensitivity to compaction, by reducing the load per wheel and increasing the contact area through the use of wide tires or half-tracks (Lüscher et al., 2015). It is recommended to avoid working on wet soils and to stop using machinery if type 3 ruts (ecological soil damage) appear (Lüscher et al., 2015). The use of branch mats is also recommended to transfer traction forces and limit pressure points on the soil, thus allowing for faster soil regeneration (Lüscher et al., 2015). Information systems such as ProFor can help assess soil trafficability before operations (Lüscher et al., 2015).
Active restoration and agroforestry : Active restoration, based on human intervention, can accelerate the recovery of degraded ecosystems (González Díaz et al., 2020). The conversion of unproductive agricultural land into agroforestry systems is encouraged (Kay et al., 2019; Barbera et al., 2024).
Cooperation and planning : The fragmentation of private forest properties in Switzerland, where most owners have small areas, makes cooperation essential for economically viable management (Thomas et al., 2019). Cooperations improve efficiency and profitability, and their number has increased significantly in Switzerland (Thomas et al., 2019). Support for forest certification initiatives (PEFC, FSC) and the promotion of mandatory forest planning are crucial for sustainable practices (Barbera et al., 2024; MASAF, 2022).
Participation in local policies : Forest diversification is not just an ecological theory; it is a concrete practice that requires patience, determination, and a long-term vision. By adopting these principles, we collectively contribute to healthier ecosystems, stronger rural economies, and a more resilient future in the face of climate challenges.

References

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This page has been written for the NBSOIL project, with the financial help of the European Union, with the help of the Centre National d'Agroécologie, of Ver de Terre Production and of Neayi