4 IMPACTS OF GLOBAL CHANGE AND ADAPTATION STRATEGIES IN
4.3 F ORESTRY
4.3.3 Baseline Situation: Forestry in Germany
With a forest area of 11.1 million hectares (ha), one third of Germany is forested.
Almost three-quarters of the forests (73%) are mixed stands. Norway spruce (Picea abies) is grown on a little more than a quarter (28%) of the forested land and is therefore the most common tree species in Germany. This is followed by pine (Pinus sylvestris) with 23%, beech (Fagus Sylvatica) with 15%, and common and sessile oak (Quercus robur and Q. petraea) with 10% (Fig. 4.3-1a; BMVEL, 2004). Forty-six percent of the forest is privately owned, 34% are owned by the federal states or the federal government, and 20% are owned by towns, communities and other corporate bodies (Fig. 4.3-1b). The forestry sector employs approximately 175,000 people and accounts for approximately 3% of gross national product (DFWR, 2001).
Recent Development
The percentage of deciduous trees, particularly of beech trees, has distinctly increased in the last 15 years, as a consequence of management measures (forest conversion programmes), while the percentage of coniferous trees decreased. Total forest area also increased slightly, on average by approximately 3500 ha per year.
(a) Tree species
Spruce 28%
Pine 23%
Beech 15%
Oak 10%
Others
24%
(b) Forest ownership
Cities, communities, other public bodies
46%
State
34%
20%
Private
(a) Tree species
Spruce 28%
Pine 23%
Beech 15%
Oak 10%
Others
24%
(b) Forest ownership
Cities, communities, other public bodies
46%
State
34%
20%
Private
(a) Tree species
Spruce 28%
Pine 23%
Beech 15%
Oak 10%
Others
24%
(b) Forest ownership
Cities, communities, other public bodies
46%
State
34%
20%
Private
Fig. 4.3-1: Tree species (a) and forest ownership (b) in Germany (BMVEL, 2004;
DFWR, 2001).
The stock of wood in German forests is high. With an average of 320 stored solid cubic meters of wood per hectare they are not only at their peak compared to historical records, but also obtain a leading position relative to European neighbouring countries.
Wood increment is also relatively high: In the old federal states an annual increment of on average 12.6 stored solid cubic meters were observed during the period 1987 to 2002 (average across all tree species and age classes). This trend has been observed for many other European countries as well (Spiecker et al., 1996). On average, only two-thirds of this increment is harvested. Since less wood is used than annual growth adds, the stock of wood and age of the forests and trees increases. This bears advantages (older forests usually are more diverse, rich in structure and store more carbon) and risks: with increasing age the susceptibility of trees to environmental stress increases and the risk of depreciation of wood through calamities increases (BMVEL, 2004).
Novel Damages to Forests
Since the mid 1970s, novel damages to forests have been recorded on wide areas within the whole of Europe. When originally mostly fir and spruce were impacted, damages now occur increasingly also on deciduous trees, particularly beech. Interplay between various abiotic influences (pollution, nitrogen deposition, weather conditions) and biotic factors (calamities) is speculated to be the root cause of this. Among these factors, pollution is seen as the most important cause. Since the mid 1980s, the health status of German forests is regularly monitored in forest damage inventories, mainly focussing on the indicator “crown transparency”.
In the year 2004, 72% of all trees exhibited distinct crown transparency or were rated as “in stage of alert”. This was the highest level of recorded damage since the beginning of forest damage inventories. For the first time, the main reason for this high level of damage in 2004 is not thought to be pollution, but the weather conditions in the hot and dry “record summer” of 2003, and its side- and after-effects. These are direct damage through drought and radiation; damage through increased ozone content of the air, as a consequence of intensive solar radiation; and the spread of calamities as a consequence of the mild winter in 2003, as well as prior damages through direct weather impacts (BMVEL, 2004).
Current Impacts of Climate Change
An early sign of climate change may be the increase of wood increment described above. The main cause of this is thought to be nitrogen deposition from the atmosphere, but the increasing warming and the elongation of the vegetation period do indeed contribute to increased wood growth. The vegetation period of the main
forest tree species in Europe and Germany has already been elongated by 10-11 days from the 1960s to the 1990s of the 20th century (Menzel, 1997; Badeck et al., 2004a).
German forests are primarily at risk through drought stress. This is true particularly for the warm and dry areas in the Northeast and Southwest of Germany. Moreover, in the Southwest spruce as the main tree species is little resistant to aridity. In the North, especially in the Northeast, sandy soils with low water holding capacity increase the risk of drought stress. Furthermore, stands close to groundwater table (lowland riparian forest) are at risk through declining groundwater tables (Gerstengarbe et al., 2003).
The heat wave in the summer of 2003 shows how strongly yield potential can be threatened by drought stress. Drought and high temperatures led to a near total depletion of the water reserves in forest soils available to plants. In August/September, the water uptake of trees in many stands was strongly impaired.
The consequent water deficiency had profound impacts in many forest areas.
Premature shedding of leaves and needles, actinocutitis (sunburn) and a general decrease of vitality of the forest trees were observed. This led to a poor status of tree crowns in 2004, but also to e.g. decreased increment and resistance to pests (BMVEL, 2004). Damages through extreme weather conditions such as in the year 2003 can continue to have an effect over more than 10 years, and can lead to changes growth trends in the long term, beyond actual reduced growth rates (Anders et al., 2004).
In 2003, the connection between drought, heat and risk of pest infestation became also apparent. An explosive propagation of pests, particularly bark beetles and nun moths (Lymantria monacha, a leave-eating butterfly, especially on spruce and pine), was a consequence of high temperatures and decreased vitality of forests in 2003 (BMVEL, 2003).
In Germany in the year of the heat wave, the area of burnt forest was also by 25%
larger than the average across 1991-2002, namely 1315 ha. In 1992 the largest area of burnt forest since 1990 was registered, with 4908 ha and an estimated damage of 12.8 million €. In this “record summer” the absolute maximum air temperature reached 39.1ºC, and the maximum of precipitation deficiency was in Northeast Germany, where stand conditions and plantation types (sandy soils, pine stands) in general cause maximum forest fire risk (Anders et al., 2004).
Almost every fire starts on the ground – it is therefore meaningful that since the last few decades undergrowth of grasses in forests is increasing and favouring two grass species that rank very highly on the scale of inflammabilty, namely wood small-reed (Calamagrostis epigejos) and wavy hair-grass (Deschampsia flexuosa). Furthermore, the grass layer contributes to increased evaporation and therefore to further desiccation. Reasons for increasing grass layer are thought to be on the one hand atmospheric nitrogen deposition and acidification, and on the other hand climate warming in combination with dryer summers. Therefore, dry summers increase the risk of forest fires not only in the year itself, but also in the following years (Anders et al., 2004).
Moreover, in recent decades, an increase in forest damages through storms was observed. Particularly in Southern Germany, the low-pressure systems “Vivian”,
“Wiebke” (1990) and “Lothar” (1999) caused disastrous damages.
The Forestry Sector and Climate Protection
Presently, German forests are a sink of carbon. Between 1987 and 2003, forests in Germany absorbed approximately 75 Mt CO2, which corresponds to approximately 3%
of Germany’s CO2-emissions during the same time (BMVEL, 2005). Therefore, the protection and maintenance of forests plays an important role in climate protection.
Further Influences on the Forestry Sector in Germany
In Germany, forests overwhelmingly are managed ecosystems. Management strategies (targeted tree species, rotation times, type of harvest) vitally determine the status of
the forest and influence the processes within it. In their turn, management strategies depend strongly on the actual conditions of the wood market. Land use changes such as afforestation, and the building of roads and settlements are further direct influences. Besides these direct human influences, forests are indirectly impacted through anthropogenic pollution (sulphur compounds, nitrogen, ozone) and changes in the water balance (melioration). Further influences are biotic factors such as pest insects and fungi, and the invasion by neophytes. Many of these factors interact.
Climate and weather extremes and the impacts of climate change act as additional stressors in concert with these factors and often enhance their impacts (e.g. risk of calamities).