Forests are exposed to multiple pressures that often act together and exacerbate impacts on biodiversity: habitat changes, climate change, overexploitation, invasive alien species and pollution or nutrient enrichment. As a result of increasing, or merely stabilized but ongoing, pressures, forest ecosystem condition in Europe continues to decline, and is considered ‘Degraded’ according to the EU ecosystem assessment.

Habitat changes

The pressure from conversion of forested land to land for other uses has decreased substantially across Europe, and on average forest cover is increasing according to the EU ecosystem assessment. Changes in forest area, as defined by the net changes in Corine Land Cover 2000-2018, show that there are several localized regions within Europe where forested area is decreasing.

Sources:Corine Land Cover Changes (CHA) 2012-2018 provided by European Environment Agency (EEA) and Copernicus Land Monitoring ServiceExtracted from Land cover and change statistics 2000-2018 provided by European Environment Agency (EEA)
Administrative Units/Statistical Units provided by GISCO Eurostat; © EuroGeographics for the administrative boundaries

While forest area is increasing, the EU ecosystem assessment found a 35% decadal increase of tree cover loss in the period between 2001 and 2018. This information is derived from Global Forest Change dataset, which enables assessment on finer spatial and temporal scales. It thus provides complementary information on forest dynamics over time, compared to the net change in forest area measured in by Corine Land Cover 2000-2018.

Forest fragmentation impacts ecological processes, such as habitat provision, gene flow, pollination, and wildlife dispersal. At a European level, almost two third of the forests form continuous areas larger than 100 000 ha (i.e. without considerable separation by other land uses). However, there is considerable variation across Europe, as in Central-West Europe continuous large area forests make up only one third of the share of forests there. This can negatively impact some species that require large continuous forest areas for habitat or for vital populations. Large areas also allow large scale natural processes to create diversity in forest composition, structure and habitat for species. The trend between 2000-2018 was stable.

Forest patch size

Forest patch size is important for nature. Large contiguous forest areas provide connectivity between areas, which supports species dispersion, gene flow and genetic adaptation. These are essential processes for viable populations and for species range shifts in adaptation to climate change. Forest fragmentation is the breaking up of larger, contiguous, forested areas into smaller patches of forest.

Forest fragmentation is likely to negatively affect forest species richness and such as wide-ranging predators

 

Climate change

Pressures from climate change on forests are increasing. The effective rainfall – the amount of precipitation added and stored in the soil – is declining, and this decline is most pronounced in the Mediterranean region but also in other parts of Europe.

Climate change accentuates previously hidden vulnerabilities from invasive alien species and pests, pollution and diseases. It affects forest fire regimes, leading to conditions under which the extent and intensity of forest fires in the EU will increase in the next years. The ability of species to disperse to new habitats with suitable climates in the face of climate change is reduced by forest fragmentation.

Abiotic damage caused by storms, forest firest or other causes in EU28

 

Invasive Alien Species

Invasive alien species are non-native plants, animals, pathogens and other species that may cause harm to the native biodiversity and ecosystems of Europe. Dense stands of invasive alien trees lower biodiversity.

Invasive alien species can also lead to high economic and health costs. Such examples include:

  • Insects that bore into the bark and wood of living trees may kill healthy trees, which in turn can alter ecosystem structure and function. Over one hundred invasive alien insect pests of woody plants have been introduced in Europe. Anoplophora glabripennis (Asian long-horned beetle) is one of the most dangerous, killing deciduous trees.
  • Ophiostoma novo-ulmi (Dutch elm disease) is a fungal pathogen that is highly contagious and lethal to European elms.
  • Cryphonectria parasitica (chestnut blight fungus) is another example of a fungus that has devastated large plantations of sweet in southern Europe.

The European Alien Species Information Network (EASIN) includes information on some 14,000 alien taxa in Europe and facilitates timely notifications of invasive alien species of Union concern as required by the EU IAS Regulation 1143/2014. Almost half of the forest ecosystem extent is affected by invasive alien species, as calculated in the EU ecosystem assessment. The widespread distribution of invasive alien species across almost half the European forest cover is particularly concerning since certain species are at higher risk of becoming invasive with climate change.

longhorned-beetle.jpg

Asian longhorned beetle boring into a tree. By R. Anson Eaglin - CC

chestnut-fungus.jpg

Chestnut blight fungus. By Joseph OBrian CC



Pressure on forests from Invasive Alien species

Source:
Mapping and Assessment of Ecosystems and their Services:

Fig. 4.2.9 of MAES assessment. This is the pressure by the 49 invasive alien species of Union concern on forests. Dark grey indicates forests where invasive alien species are not reported

The IUCN European Red List of trees recognizes about 150 invasive alien tree species in Europe. Dense homogenous stands of invasive alien trees pose serious risk to forest habitat types protected by Article 1 of the Habitats Directive. Robinia pseudoacacia (black locust) is the most commonly reported invasive alien species covering more than 1.4 M ha. Ailanthus altissima (tree of heaven) is another frequently reported invasive alien tree species. In spite of its modest coverage, it is considered as very aggressive due to its fast-spreading and toxicity. Many other invasive alien tree species are black-listed or controlled in Europe, including Acer negundo, Acacia spp., Prunus serotina, and Quercus rubra.

Forest condition variable account for EU28 (spatially averaged values)

Condition group

Condition class

Descriptor

Units

Opening stock (2010)

Closing stock (2020 - projected)

Change (% per decade)

Confidence

No results

Source: Extracted from Accounting for ecosystems and their services in the European Union (INCA) - 2021 edition published by EUROSTAT