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Forest condition

Last update of indicator20.12.2021

Indicator definition

This indicator assesses the condition of forest ecosystems and its development based on the proportion of defoliated trees in the levels of damage 2 – 4 (defoliation more than 25%) and 3 – 4 (over 60% – strongly damaged trees), both in total and separately for coniferous and broad-leaved trees.




Related policy documents and targets

Climate Change Adaptation Strategy of the Slovak Republic - Update (2018)
Design of adaptation measures in forestry:

  • Appropriate integration of adaptation measures into the concept of stand reconstruction and management of calamity situations in areas with degraded forest condition and persistent pest calamities (Orava, Kysuce, Spiš)
  • Optimise forest research and monitoring practices in the light of climate change risks and other forest management priorities, and adapt forest planning and management to the needs and results of research and monitoring
  • Build demonstration facilities for adaptation of forest plantations to climate change.


Concept of Agricultural Development of the Slovak Republic 2013 – 2020 (2013)

Ensuring sustainable forest management - Ecological aspect of sustainable forest management

Priority tasks:

  • To promote the conservation and sustainable use of genetic resources of forest trees (ensuring sufficient quantity and conservation of genetic resources of forest trees, to support the establishing of new and protection of existing sources of genetic resources of forest trees, especially in areas damage by harmful agents)
  • To restore the functions of forests in areas affected by disasters, and increasing the stability of forest stands.


Action plan of the National Forest Programme of the SR for the period of 2015 – 2020 (2015)

Strategic goal 2: Improvement and protection of the environment

Priority 5: To increase forest protection

Framework target (2.10): Creating the effective system of creation, financing and implementation of projects of remedial measures in forests aimed at the prevention and renewal of the forest potential after calamities caused by harmful agents

Framework target (2.11): Creating and financial ensuring of the effective system of forecasting, prevention and monitoring of forest fire origination

Framework target (2.12): Creating legal, economic and technical conditions for the system solution of calamity situations in protected areas

Framework target (2.13): Support of the system of measures aimed at forest regeneration and tending after wind and insect calamities

Priority 6: Develop forest monitoring

Framework target (2.14): Ensuring the complex system of forest inventory and monitoring at the national level in accordance with procedures and requirements of the continuing pan-European and global integration process


  • Ensure implementation of the project National forest inventory and monitoring (NIML) of the Slovak Republic as a long-term programme (the 2nd cycle of NIML SR)
  • Continue in the development of methods of forest inventory and monitoring in accordance with procedures, technologies, needs and requirements of the continuing integration process
  • Ensure continuing of the forest health monitoring of the 1st and the 2nd levels by annual monitoring and evaluating.


The updated National Biodiversity Strategy to the year 2020 (2014)

Main goal by 2020

Halting biodiversity loss and degradation of ecosystems and their services in the Slovak Republic until 2020, ensuring the restoration of biodiversity and ecosystems to an appropriate extent and the prevention of biodiversity loss on a global scale.


Key question

Has the forests condition been improving?

Key messages

  • The forest health of Slovakia characterized by the defoliation rate continues to be considered as unfavourable, while it was still worse than the pan-European average.
  • For coniferous tree species, spruce and fir, it is possible to observe stabilization of the health condition already from 1996, but it deteriorated for broad-leaved tree species.
  • In the medium term (since 2005), there are significant fluctuations in defoliation of deciduous and coniferous trees, which are probably related to current climatic conditions (especially drought). However, the trend of forest damage has been increasing, with a peak in 2014, which was, or is, mainly due to the deterioration of deciduous trees.
  • Year-on-year (compared to 2019), the health status of conifers has deteriorated again, while deciduous trees have seen improvement. The proportion of trees in defoliation stages 2-4 increased for all tree species by 1.8% to 40.4% (the proportion of conifers in these stages increased by 6% to 51.3% and deciduous trees decreased by 1% to 33.8%).
  • Among conifers, defoliation has been declining in long term in case of fir, is stable in case of spruce, and has been declining significantly over the long term in case of pine since about 2005. For all the most abundant deciduous trees (oak, beech and hornbeam), defoliation has an increasing (worsening) trend. The most damaged deciduous tree is oak.
  • The areas with the long-term worst condition of forests in Slovakia remain the areas of Kysuce, Orava and the Spiš-Tatra that relate to massive disintegration of spruce forest covers.


Change since 2005 Change since 2015 Last year-on-year change
emo_sad emo_sad emo_sad
Forest health, as indicated by defoliation, has steadily deteriorated with occasional fluctuations, reaching the highest level of damage in 2014 over the whole period under study. In the medium term, tree defoliation fluctuated, with a slightly increasing tendency. There has been a general year-on-year deterioration in forest health, mainly related to the deterioration of coniferous trees.


Summary assessment


Detailed assessment

In the SR there is a high proportion of forest ecosystems in the country. Forest cover has been around 41% for a long time. According to the World Wide Fund for Nature (WWF), Slovakia has – after Sweden and Switzerland – the most preserved forests in Europe. Nonetheless, the state of forests in Slovakia is distorted. Persisting malfunctions of forest ecosystems have ultimately led to their gradual degradation and breakdown – in 1989, 85% of the forests in Slovakia showed the symptoms of damage.

The current unfavourable forest condition is caused by synergic effects of various harmful agents. In addition to climatic changes and weather fluctuations in the individual years, the very negative impact is mainly attributed to long-term most important harmful agents, i.e. wind and insect living under bark.

The basic element of the evaluation of the health condition of tree species is the visual evaluation of the condition of tree crowns, specifically loss of assimilation bodies (defoliation). Defoliation reflects both internal and external influences of factors (mainly genetic, climatic, habitat, air pollution) that affect the condition of individual trees. In the Slovak Republic, defoliation assessment is carried out annually on 107 permanent monitoring sites, using an international 5-class scale. The decisive factor is the proportion of trees in level 2 4, i.e. with defoliation greater than 25 % (trees with lower defoliation are considered healthy).

The worst condition of forests is at the upper limit of forests where they fulfil extraordinarily important society-wide functions and where the acute disintegration of ecosystems threatens.


Trend in average defoliation of coniferous trees, broad-leaved trees, and total

Trend in average defoliation of coniferous trees, broad-leaved trees, and total
Source: NFC


The defoliation trend for both groups of tree species shows a similar pattern, with a decline in average defoliation until around 2000 to 2005, followed by a steady increase up to the present.

The average defoliation of conifers is higher than that of broad-leaved trees (with the exception of 2013), reaching 31.3% in 2020, the highest in the last 25 years (32% in 1995). The average defoliation of broad-leaved trees in 2020 was 25.8%.



Broad-leaved tree species resist better to unfavourable factors, which is also related, among other things, to difference in the persistence time of the assimilation organs compared to conifers. Nevertheless, they have also been in declining condition since 2005.

In the group of coniferous woody plants, it is possible to observe stabilization of the health condition from 1996 with the trend of deterioration after 2005.


International comparison



Mgr. Peter Kapusta, SAŽP,

Related definitions:

Defoliation is the loss of assimilation organs. It is a leading indicator and basic, visually assessed symptom of forest condition. This is a parameter reflecting the internal and external impacts of factors affecting the life of an individual (genetic, climatic and habitat impacts, air pollution impacts, etc.). To classify the defoliation, an internationally established 5-class scale is used.



Among the basic characteristics of forest land we recently include also the condition of forests. It has been evaluated for a long time in the context of the National Programme for the monitoring of forest ecosystem condition, which is implemented on 112 permanent monitoring sites (PMS), in a network of 16 x 16 km (extensive monitoring), and on 7 research PMS (intensive monitoring). Both monitoring levels are the part of a European network of observation plots within the UN/ECE ICP Forests program (39 countries participate here).

The loss of assimilation organs (AOL) is used as the basic evaluation symptom – defoliation, and it is evaluated by a visual estimation in percentage, rounded to the nearest 5%. The trees are classified into internationally established 5-class scale of damage:

Level of defoliation AOL (%) Defoliation level described in words
0 0 – 10 No defoliation
1 11 – 25 Slightly defoliated
2 26 – 60 Moderately defoliated
3 61 – 99 Highly defoliated
4 100 Dying and dead trees
To assess the state of forest condition, the share of trees in the level of damage 2 – 4 is crucial, namely with the defoliation of more than 25%. For trees with lower defoliation, the loss of gain does not occur in general, and they can be regarded healthy.


Data sources:

NFC (National Forest Centre)


Linked references: