European inventory signals vulnerability of forest stocks

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Jan van Staalduinen, Friday 9 January 2026

210 sec

Climate change puts regeneration of European forests under pressure

Biodiversity and vitality of forests are closely linked to the success of regeneration. Young trees in particular are struggling due to prolonged dry and very warm summers, which are occurring more frequently as a result of climate change. This worrying trend emerges from an inventory carried out in eleven European countries. Gert-Jan Nabuurs, professor of European Forests at Wageningen University & Research (WUR), explains where the problems lie and what is needed to reverse the trend.

Gert-Jan Nabuurs (WUR)

WUR is one of the forest inventory institutes in eleven EU countries involved in the periodic inventory. 'It is a legal obligation to do this once every five to ten years, and I fully support that,' says Nabuurs. 'For forest managers, policymakers and other stakeholders, it is crucial to have insight into health status and trends. A large-scale, periodic inventory provides the data and insights needed to develop policy and adjust course where necessary.'

Large-scale inventory

Almost all EU countries carry out such an inventory. Forests are measured in small plots, totalling around 500,000 plots. For this study, data on young trees from 95,000 plots in eight countries were used. These forests are under heavy pressure from climate change. Of the total European forest area of around 165 million hectares, approximately 300,000 hectares have been lost in recent years due to forest fires alone.
Nabuurs: 'That amounts to 0.15 percent. It may seem small, but the scale and impact of forest fires are increasing rapidly, mainly due to prolonged warm and dry summers. The impact is much broader than fires alone. Forests changing is normal. What is worrying is that we are seeing an acceleration in the wrong direction.'

Modelling

Forest regeneration, the process by which new trees establish and begin to grow, is crucial for future forest structure, biodiversity, growth and resilience. When new trees start growing, this marks the beginning of an important process. This phase is decisive for the future forest. To make forest regeneration at European scale more predictable, scientists are working on modelling the ecological processes that drive regeneration. 'Existing approaches are often based on the locations where species are currently found,' says the professor. 'In light of the increased dynamics caused by climate change, that is no longer sufficient to keep our forests diverse, vital and resilient.'
The researchers, within the WUR team particularly PhD candidate Louis König, analyse how climate and weather conditions affect regeneration and how this influences current forest structure using a dedicated model. The model predicts which species will grow where, how many young trees will emerge and in which forest types they thrive. According to Nabuurs, the development of this predictive model, fed by extensive datasets, is an important step towards sound long-term forest management.

Climate is crucial

The analysis shows that climatic conditions are very important for the success of young trees. Forest regeneration is successful under stable climatic conditions and with ample rainfall. Under the extreme weather conditions seen more frequently over the past ten years, especially prolonged high temperatures and drought in spring and summer, natural regeneration comes under pressure. The analysis also shows that broadleaf species have better chances at slightly higher-than-average temperatures, which also demonstrates their adaptive capacity.
#PGrafiek bosverjonging

'One extreme drought period can cause certain species to disappear completely; that determines that part of the forest for decades'

Regenerating mixed forests

Nabuurs: 'The composition of young trees is highly dependent on the composition of the old forest. This is worrying, because a large part of European forests consists of only one conifer species, such as Norway spruce. The adaptive capacity of these trees is usually lower than that of broadleaf species. Mixed forests showed more regeneration. From the data we learn that current drought not only reduces growth in mature trees, but particularly affects the small, younger trees. One extreme drought period can cause certain species to disappear completely; that determines that part of the forest for decades.'

Pilots in the Netherlands and monitoring

The model and its predictions allow long-term management to be better guided. Forest management in Europe will need to create more space for broadleaf species and mixed forests. This requires good knowledge of management practices and of which species are likely to perform well at a given location in the future.
The professor says it is encouraging that a European Forest Monitoring Law had been under consideration, aimed at improving cross-border coherence. 'National data are not yet shared structurally, and that would be desirable,' he says. 'There are already contacts with the wood-processing industry, which is also an essential link in this story. After all, a large proportion of forests are production forests. However, the Forest Monitoring Law was rejected by the European Parliament and the member states on 20 October last year. Partly in response, since 2024 we have been working on better organising the inventory institutes. We are now united in an association called ENFIN (European National Forest Inventory Network).'
In the Netherlands, a programme of climate pilots funded by the Ministry of LVVN has been running since 2018 at Wageningen Environmental Research. These pilots involve planting fewer Scots pines and more broadleaf species such as aspen and pedunculate oak. Erik Roest leads this programme.

Message for nurseries

Asked about the contribution the Dutch tree nursery sector could make to improving forest vitality and biodiversity, Nabuurs replies: 'Ensure a broad assortment with somewhat more southern species. The variety list also contains information on regions of origin. Heat-loving species are slowly shifting northwards; they will need to be planted more often to maintain good regeneration and sufficient biodiversity. Demand for conifers from forestry will probably decline. I say this as a scientist; I am less familiar with the commercial side. So don't move too fast, but be aware that changes are under way.'

Change in composition

The graph above shows the change in composition of young trees as maximum monthly temperature increases in Central Europe. For example: top row: 'Norway spruce'. A shift from 15 to 20 degrees already results in a change in forest regeneration from mainly spruce and birch to a much more mixed regeneration of spruce, birch, beech and other broadleaf species. In a monoculture (bottom row), regeneration remains much more limited to a single conifer species, with Norway spruce and Scots pine dominating.

This article was previously published on 29 January 2026 on the Boom](https://www.boom-in-business.nl/article/52462/europese-inventarisatie-signaleert-kwetsbaarheid-bosbestanden]Boom) In Business website.

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