Over the past decades, both the total forest area and the standing volumes have increased. More forests are now allowed to grow into older development stages, which have positive effects on forest biological diversity. Afforestation programmes as well as decreasing grazing pressure lead to large‑scale conversion of mainly former agricultural land.
Nevertheless, afforestation may also threaten existing biodiversity values in some localities, such as peatland when it is combined with draining. Animals and trees are both under threat So far, Europe's efforts in halting biodiversity loss in forests has had mixed results. According to IUCN, 11 mammal species depending on forest in some stage of their life cycle should be considered as threatened, including the 'critically endangered' Bavarian vole, Microtus bavaricus and Iberian lynx, Lynx pardinus. In the case of forest birds, common populations show a decline in north and south Europe, while they are largely stable in the West and East.
Managed forests in Europe are increasingly becoming more diverse, often with a mixture of coniferous and broadleaved tree species. On the other hand, concerns are raised over the genetic diversity of the commercially important trees, especially in connection with the widespread transfer of tree genetic material between countries and regions.
The rate of introduction in recent decades of really problematic alien species known as 'worst invasives' has been less dramatic in forest ecosystems than in other ecosystems. Although European forestry is largely based on native tree species, deliberately introduced tree species are important in some countries. Countries classify only a minor part of the area covered by introduced forest tree species as occupied by invasive trees. One of the countries reporting substantial areas occupied by invasive tree species is Italy.
Climate change will affect biological diversity
Climate change will add to increased abiotic and biotic disturbances, including drought, salinification, increased spring and autumn frost risk, and insect and pathogen damage. The changes will also effect the biology, phenology, growth and distribution of species and the species composition of forests in Europe. Changes in the frequency and degree of extreme climatic events (such as droughts and floods) may have a greater effect on forest ecosystems than the changes in the projected average climate. The effects of climate change have to be approached through adaptation measures such
as ensuring connectivity to facilitate migration of species.