Forest health: what did 2024, the wettest year on record, bring?
The annual forest condition survey is part of the international programme ICP Forests, which celebrates its 40th anniversary this year. The Flemish forest condition monitoring network comprises 78 sample plots. We inspect the trees in the monitoring network every year and assess their crown condition according to a fixed protocol. A tree with more than 25% leaf or needle loss is considered damaged.
In 2024, 22.4% of the 1,476 trees surveyed were damaged. Among deciduous tree species, pedunculate oak had the highest proportion of damaged trees Among coniferous tree species, this was Corsican pine. ‘Damaged’ does not mean that a tree is dying. The mortality rate has varied between 0.5% and 1.2% over the last 10 years. In 2024, it was 0.8%. The proportion of trees with more than 60% leaf loss also remained limited to 0.7% in 2024.
For all trees combined, there were only minor differences compared to 2023. The proportion of damaged trees increased by 0.4 percentage points and the average leaf loss by 1.2 percentage points. The proportion of damaged trees increased for pedunculate oak, beech and the group ‘other deciduous tree species’, a collection of less represented species. There was a decrease in damage to American oak, Scots pine and Corsican pine. Various factors explain these short-term differences, such as the occurrence or absence of extreme weather, fungal infection, insect damage and seed production.
2024 was exceptionally wet. Until the end of summer, precipitation in Uccle was above average every month. The high rainfall did not adversely affect the health of the trees in the monitoring network. However, we did notice storm damage in several monitoring plots.
Geert Sioen, Pieter Verschelde
Image above: forest condition monitoring plot in Moerbeke (Heidebos, August 2024)
