FW-I-4: Damaged timber – extent of random use

The picture shows a forest with beech trees. Numerous trees lie uprooted on the ground.Click to enlarge
While in full foliage, beech trees on wet soil fell victim to the storm Xavier in early October 2017
Source: Photograph: © Tanja Sanders / Thünen-Institut

2019 Monitoring Report on the German Strategy for Adaptation to Climate Change

Table of Contents


FW-I-4: Damaged timber – extent of random use

Random use owing to wind-blown, wind-broken and infested timber is detrimental to forestry in many ways. A trend towards more random use of timber has not emerged so far. However, strong winter storms which occurred especially in 1990, 1999, 2007 and 2010 resulted in considerable volumes of damaged timber.

In a stack column diagram, the share of all incidental uses in the total felling is shown in percent from 1991 to 2012.
FW-I-4: Damaged timber – extent of random use

In a stack column diagram, the share of all incidental uses in the total felling is shown in percent from 1991 to 2012. Accidental uses caused by wind/storms and other causes add up to 100 percent in the bars. The proportions vary greatly between the years. The share of wind/storm was highest in 1991 with 82 percent, in 2000 with 93 percent, in 2007 with 90 percent and in 2008 and 2009 with about 72 percent each. A trend has not been discernible so far. An additional line represents the share of incidental uses in the total logging in percent. It shows a course with strong fluctuations and is without trend. Particularly high values were recorded in 1991 with 67 percent, in 2000 with 55 percent and in 2007 with 45 percent. The values in the other years fluctuate between 10 and 40, but mostly between 10 and 20 percent.

Source: BMEL (compilation based on federal state information); BMEL and StBA (timber logging statistics)

Forestry becomes riskier

The long rotation cycles involved in forestry require very careful and long-term planning of forest management; and only if planned actions can be implemented will it be possible to achieve the desired cultivation objectives. Climate change can impact in two ways on the ability to plan the utilisation of commercial forests in line with forestry principles. On one hand, changed weather patterns can weaken trees thus making them more vulnerable to damage, especially infestation with insects. On the other, it is assumed that the frequency and intensity of extreme events such as storms will increase as a result of climate change.

Both types of development can lead to increased incidence of wind-blown and wind-broken timber and to forced usage after pest infestations. This type of timber jeopardises the chance of safeguarding the ongoing production as it offers breeding habitat for bark beetles. In addition it is worth noting that any random use of timber represents a burden on the entire forest ecosystem which in turn is detrimental to the medium- and longterm productivity of a forest. It makes ongoing cultivation more difficult and represents a safety hazard for forestry employees and forest visitors.

This is why wind-blown and wind-broken timber has to be removed from commercial stands. Especially after major damage events such random use of timber tends to tie up considerable capacity required for other forestry operations. This diverted capacity is then unavailable for implementing targeted cultivation measures which are, after all, of great importance in achieving the required adaptation to climate change. As a rule it takes several years until the consequences of calamities have been dealt with enabling foresters to return to planning and managing ‘normal’ utilisation and cultivation actions.

For the forest owner – no matter whether it is the state, the local community or a private forest owner – major volumes of wind-blown, wind-broken and infested timber are associated with considerable revenue shortfalls. In fact, the restoration costs in damaged stands are distinctly higher and the timber qualities often inferior. At the same time, timber prices decline distinctly, especially in the aftermath of major damage events. Besides, timber will have to be stored longer and this causes additional costs. In fact, this is why in late 2018, a new eligibility status for funding – entitled ‘Promotion of measures to deal with the consequences of extreme weather events in the forest’ – was agreed as part of IASCP and endowed with additional funding from Federal Government sources amounting to 10 million Euros for 2019.

Even though there is no statistically sound evidence for a trend developing over the past barely twenty years towards increases in the extent of random use of timber, forestry circles have gained the impression that phases without any relevant influences of forced usage are becoming ever shorter.

The extremely high proportion of random use as part of the total removal of timber is caused mainly by windblown and wind-broken timber, i.e. it is brought about by storms. For example, in late winter of 1990 hurricanes Vivian and Wiebke resulted in extensive restoration work required in the following year of 1991, and this extended to major parts of Germany. In December 1999 Lothar devastated extensive parts of south-west Germany. In January 2007 cyclone Cyril destroyed forests particularly in North-Rhine Westphalia with a focus on Sauerland. In late March 2015 hurricane Niklas wrought havoc in Bavaria but left behind smaller amounts of damaged timber than comparable hurricanes. In early October 2017 the autumnal storm Xavier caused damage in deciduous woodlands in Brandenburg while trees were still fully covered in foliage. It is expected that the 2018 statistics will show an increase in storm-related volumes of damaged timber resulting from hurricanes Friederike and Burglind which struck the country in January. In years without supraregionally important storm events the bulk of random use is due to damage by insects. In this context, the drought year of 2018 is expected to reveal a major increase in damage.

In evaluating data on wind-blown, wind-broken and infested timber it is important to remember that, as a rule, these data do not provide a comprehensive overview of the actual damage caused to timber. Not all Federal Länder provide data on private and corporate forests in addition to data on state-owned forests. Besides, the focus of data collection has so far been on winter storms. Apart from impacts caused by climate change, there can also be other trends exerting strong influences on the time series. As far as the age structure of German forests is concerned, stands tend to contain the older range of the spectrum. It is important to note that older trees are more vulnerable to wind-blow than younger ones, and the greater the timber reserve, the greater the volume of damaged timber. The latter can also mean that depending on where the calamity is located, the damage caused can vary in terms of volumes. For example, storms in regions with fairly open stands of pine forest which are widespread on sandy soils in Brandenburg or Mecklenburg-Vorpommern, will cause smaller volumes of damaged timber than storms in the Black Forest with its high volumes of timber.



FW-I-5: Extent of timber infested by spruce bark beetle - case study



Aiming for particularly stable mixed stands with increased resistance to widespread misadventures caused e.g. by storms and bark beetle infestations (DAS, ch. 3.2.7)

Cultivation of site-appropriate tree species with high resilience and growth performance (Waldstrategie 2020, p. 23)