Insufficient rain for tree recovery

Eberswalde (June 11, 2025). The dry years of 2018 to 2020 and 2022 left a lasting impact: since then, scientists recorded a significant increase in the level of damage in the annual Forest Crown Condition Survey. Alongside this trend, the proportion of spruce is decreasing. However, there is also good news: Forests are becoming more and more diverse. This is shown by the data from 2024, analysed in the current Forest Crown Condition Report by the Thünen Institute on behalf of the BMLEH. Yet, the challenge remains to reforest the damaged area to guarantee their development into climate-stable mixed forests providing important ecosystem services such as carbon storage or enabling sustainable wood utilisation.

The weather in 2023 and 2024

According to the German Weather Service (DWD), 2023 set a new record. It was the warmest year in Germany since records began. However, in contrast to the previous warm years of 2018 to 2020, it was not characterised by droughts and heatwaves but by warm and humid weather with large amounts of precipitation.

Spring 2024 was once again a record-breaker: It was the warmest spring since weather recording began in 1881. Some regions experienced ample extreme rainfall events, especially in May following heavy thunderstorms. Heavy continuous rain led to dramatic flooding in areas of the Saarland and Rhineland-Palatinate. Oak trees in particular suffered from the late frost in April.

Significant defoliation remains high

Although the weather in 2024 was favourable, it did not turn the trend persisting since 2019 and the proportion of trees with a significant crown defoliation remained at a high level. As in the previous year, 36 per cent of the trees showed a significant defoliation. Defoliation is classed as significant when the defoliation is above 25 per cent. 43 per cent of the trees fell in the warning level (over 10 to 25 per cent defoliation) (previous year: 44 per cent) and only 21 per cent of the trees were without damage signs.

Within the sample, trees older than 60 years show a higher than average defoliation. They are as well more likely to show previous damage and seem to lack the ability to recover. 43 per cent of them show a significant defoliation. By comparison, only 16 per cent of the trees under 60 years of age had significantly defoliated crowns.

Mean defoliation of individual tree species

Compared to the previous year, the researchers found a slight improvement in the average defoliation of spruce and the so-called 'other broadleaved species' such as ash, birch, alder, and others. The proportion of moderately damaged spruce trees decreased from 28.6 to 27.2 per cent. The defoliation of 'other broadleaved species' decreased from 26 to 23.6 per cent. The apparent improvement of spruce could, however, also be an effect of the widespread spruce mortality as dead trees are being replaced by young ones.

Pine and beech showed roughly the same level of average defoliation in 2024 as in the previous year: 22.5 per cent for pine and 28.5 per cent for beech. Pines had the best average crown condition among the species groups analysed, even though their condition has deteriorated significantly since 2019.

Oaks also fared considerably worse. The proportion of trees with medium defoliation increased from 27.6 per cent to 29.3 per cent. The proportion of so-called 'other conifers' such as larch, Douglas fir, and silver fir also increased - from 22.7 per cent to 25.3 per cent.