This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Old-growth forests are some of Europe's most valuable natural ecosystems, but they are also among the most threatened. Their role in conserving biodiversity, regulating the climate, preserving cultural heritage and supporting people's well-being is invaluable.
According to a rough estimate, only around 3% of Europe's forests meet the criteria for primary or old-growth forests, and their extent continues to decline rapidly in Northern Europe. The importance of old-growth forests for biodiversity is linked to their structural diversity and the ecological processes that have developed over long periods. Dead and old trees, as well as deadwood, provide habitats for many species.
Fungi, lichens, mosses, deadwood-dependent insects and many cavity nesters are particularly reliant on the conditions typical of old-growth forests. In naturally developed boreal forests, tree stand structure can vary considerably. Younger trees may make up a large part of the canopy, even where the forest also contains many old trees and shows ecological processes characteristic of old-growth forests.
"In Finland, the mandatory criteria for old-growth forests set by the government emphasize the average age of the dominant tree stand and the total volume of deadwood per hectare," says Mikko Mönkkönen, professor of applied ecology at the University of Jyväskylä. "These criteria alone are not particularly effective for identifying old-growth forests. Deadwood volume varies considerably between forest types and geographical zones, as well as according to the forest's disturbance history, making it difficult to establish precise volume thresholds.
The key to identifying old-growth forests is to view the forest as a whole and consider the overall picture formed from a range of characteristics." The EU Biodiversity Strategy for 2030 and the EU Forest Strategy for 2030 require member states to define, map and strictly protect all remaining primary and old-growth forests. The Renewable Energy Directive (RED III) also prohibits logging in such forests. The EU Restoration Regulation does not explicitly mention old-growth and primary forests, but it prohibits the deterioration of habitat types in good condition as defined in the Habitats Directive.
The criteria for old-growth forests proposed by the research group help assess the condition of forest habitats. According to the European Commission's guidelines, a forest stand is considered an old-growth forest if it meets all three main indicators and at least two of the four complementary indicators. The three main indicators are native tree species, deadwood and old trees, while complementary indicators are natural regeneration, structural diversity, habitat trees and indicator species.
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