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Environmental information systems
Soil degradation occurs when the state of soil health is so reduced that it affects the ecosystem’s capacity to provide biological productivity or ecological integrity.
In all land cover classes, forest soils are among the least degraded. However, more than 35% of European forest soils are still considered degraded (unhealthy), and this share is likely to increase in the coming years due to the continued implementation of unsustainable land management practices. Key processes that contribute to soil degradation are pollution, compaction, erosion and the loss of soil organic carbon.
ADD INTERACTIVE GRAPH titled: More than 35% of European forest soils are considered degraded, however many other land use classes are doing even worse.
Soil pollutants
Pollution is a major chemical cause of soil degradation. It affects soil quality, tree and vegetation growth, quality of timber products, soil microorganisms, plant communities, wildlife and human society. It has a significant impact on the provision of other forest functions like water resources and recreation.
ADD INTERACTIVE GRAPH titled: Approximately 9.9% of forest soils have an unhealthy polluted (contaminated) status.
Heavy metals
Heavy metals contamination of forest soil is one of the main factors contributing to soil quality decline and loss of biodiversity as it can lead to biotoxicity, disrupting crucial ecosystem functions such as nutrient cycling and decomposition. Human activities are a major influence on the presence of heavy metals in the soil. Industrial activities like mining can increase the soil metal concentrations of cadmium, mercury, and zinc, while agricultural activities, such as using pesticides and fertilizers can increase soil concentrations of arsenic and copper.
Pesticides
The use of pesticides could promote negative impacts on forest plant diversity and the health of wildlife populations, causing far-reaching consequences of soil contamination on forest ecosystems. The use of some chemicals is controlled by country regulations and global conventions. For example, lindane and other forms of hexachlorohexane (HCH) were produced and used as a broad-spectrum insecticide, applied in forestry for defoliation and pest control, and to protect and preserve wood. Lindane and HCH were banned in the EU in 2000, however there are still found contaminating soils across Europe.
Acidification
Forest soils acidification is induced by deposition of nitrogen and sulfur and causes a decline in soil biodiversity. Acidification leads to a decline in sensitive plant species and overall biodiversity, leaving only species that are tolerant to high acid levels. Acidification of the soil was one of the main causes of forest dieback in European forests in the 1980s. Acid rain, containing also nitrate, sulphur and phosphorus molecules, impacted the forests significantly on a global level. The recovery of forest soils is on-going, and while the base cation pools have increased over time, forest ecosystems have far from recovered. Vulnerable soils still have a low resilience to acidification inputs.
Salinisation
Salinisation is the infiltration of soluble salt into the soil, which has a harmful impact on most freshwater-based plant ecosystems. It reduces the fertility and productivity, and can even lead to desertification. This can occur e.g. in arid regions with high evaporation and limited precipitation, in coastal regions where seawater infiltrates soil profiles due to reduced freshwater pressure and rising sea levels, or due to anti-icing and de-icing road treatments. Also putting out wildfires with seawater in absence of sweet water in arid regions will lead to salt input to the soil. While salinisation is considered a significant problem in several European countries, the problem is more connected to agricultural practices and has a reduced impact on forests.
Soil compaction
Soil compaction is the process by which soil particles are pressed closer together, reducing pore space (especially air-filled pores), often caused by machinery, livestock, or foot traffic. Soil compaction harms forest soils by making them dense (high bulk density), which lowers the space for air and water to move through. This leads to more water running off the surface, soil erosion, and areas where water collects too much. These problems make it harder for tree roots to grow, reduce how well forests grow, and disturb hydrology in the area. Compaction usually happens because of heavy machinery and frequent livestock movement, which compress the soil particles and reduce pore space.
Natural processes such as freezing, swelling, and biological activity can help recover the soil from compaction and deformation. However, natural recovery is generally a slow process, taking anywhere from at least 10 years to several decades.
Soil erosion
Soil erosion in forests occurs when the protective plant cover is disturbed, leading to the removal of soil particles by wind, water, or human activities. Undisturbed forests generally produce the least amount of runoff and soil erosion among all land use systems.
Healthy forests play a crucial role in preventing erosion by stabilizing soil with their root systems and absorbing rainfall. However, activities like logging, clearcutting, recreation, construction, and fire can expose the soil to erosive forces. Also, a changing water table of rivers or lakes can result into shoreline erosion. Over time, erosion can decrease soil quality, leading to decreased productivity and diversity of plants, animals and microbes in forest ecosystems. Erosion also disrupts hydrological cycles, reducing water quality and hindering forest regeneration.
Effective forest management practices are essential to minimize soil erosion and maintain forest health and resilience. The majority of European forested areas experience very low soil erosion, with 98.64% showing minimal erosion and only 1.13% having low erosion. Just 0.15% of the area experiences moderate erosion, and 0.07% faces high erosion rates.
INSERT GRAPH WITH Title: Forests typically generate the lowest levels of soil erosion (here expressed as modelled soil loss potential) compared to other types of land use
Loss of soil organic carbon
Soil organic carbon (SOC) refers to the carbon stored in soil as a result of the decomposition of organic matter derived from plants, roots, and microorganisms. SOC represents the largest terrestrial carbon pool, often exceeding the carbon stored in the aboveground biomass such as stems, branches and leaves. Preventing SOC loss is crucial, as it not only supports soil health and fertility but also plays a vital role in the climate regulation function of forest ecosystems.
SOC levels are influenced by natural forces like wind and water, and especially by land management practices. Clear-cutting and whole-tree harvesting lower SOC by removing large amounts of biomass and disturbing the soil, which accelerates carbon loss through erosion and decomposition. This decline in SOC reduces soil health, limiting moisture retention and biological activity. In contrast, practices like stem-only harvesting and maintaining continuous forest cover help retain organic matter and protect soil structure. Improving land use and preserving logging residues can enhance SOC stocks, support soil quality, and help reduce atmospheric CO₂.