How forest saves water protection

What does the forest do for us?

The forest has always played an important role for people. It is deeply rooted in the culture of our country. The words tree and forest are found in many idioms, proverbs, place names, and family names. Trees and forests are indispensable in poetry, fairy tales, literature and painting.

In addition to the centuries-old use of the forest, the forest and forest operations provide society with a number of other products and services - mostly free of charge. These include:
  • Recreation:
    Provision of a diverse recreational area;
  • Natural reserve:
    Provision of a habitat for many (also rare) animal and plant species;
  • Soil protection:
    e.g. erosion and avalanche protection;
  • Climate protection:
    Positive effects on global, local and regional climate; Effect as a noise filter, dust filter, pollutant sink, CO2-Sink;
  • Drinking water:
    Promoting high quality drinking water;
  • Flood protection:
    Protection against floods, especially against the occurrence of floods;
  • Cultural assets:
    Protection of cultural monuments and traditional economic forms (e.g. protection of barrows, preservation of forest sites with the economic form of the coppice);
  • Other:
    Provision of non-wood products (e.g. decorative twigs, venison)


1. Usage function:
Wood is one of the few renewable raw materials that we can grow to a significant extent. Wood is the raw material for the wood and paper industry and thus the basis for the income of forest owners. The entire economic sector, which is based on the raw material wood, employs around 1.2 million workers and achieves an annual turnover of 168 billion euros (2008) - especially in rural areas (Forest Report 2009). The sale of wood is the main source of income for forestry, which also finances measures for the protective and recreational functions of the forest.
2. Protection function
Depending on the location (rivers, mountains), forests take on protective functions that are of great importance for people and the environment. Healthy forests protect the valleys from avalanches, mudslides and floods. For many animal, plant and mushroom species, the forest is the habitat that offers them food, shelter and protection.

2.1. Water protection

One of the most important welfare effects of the forest is its ability to store and purify water. Precipitation in the forest does not simply run off as surface water and lead to soil erosion, but almost completely seeps into the soil. With the help of the humus, interspersed with root canals and animal tunnels, the forest floor can also absorb large amounts of water, e.g. after continuous rain and meltwater, and protect against flooding. These can be stored for a long time, so that even rivers and streams carry sufficient water during longer dry periods and springs and groundwater can be fed.
At the same time, the forest has a strong biological filter effect. It cleans the seepage water on the way to the streams. Water that seeps into the forest and filtered through the ground is rich in oxygen, clean and ideally suited as drinking water.
The enrichment of drinking water and groundwater is higher under deciduous forests than under coniferous forests.
Due to the stronger evaporation in spruce monocultures in the crown and soil area, only 305mm or 33% of the rainwater seeps into the soil with an annual rainfall of 920mm. 34% or 312mm evaporate and 33% or 303mm use up the tree and herbaceous layer.
In the case of a beech stand, the formation of new groundwater is much higher. With 920mm annual precipitation, 47% or 430mm drain into the groundwater, only 18% or 166mm evaporate and 35% or 324mm use up the tree and herb layer. Beech forests are therefore “drinking water forests”. (Source: German Forestry Council)

2.2 Soil protection
Due to the water retention capacity of the forest soil, the forest protects the landscape from soil erosion (= erosion) by rapidly draining surface water.
The forest can also prevent the risk of ground slides, as the widely ramified root network of the trees gives the ground support.
Due to their more intensive root penetration, the deciduous tree species contribute more to soil protection than the coniferous tree species. But intact mixed coniferous forests also provide protection against mudslides and avalanches in the high mountains.

2.3 Climate protection
The forest compensates for daily and annual temperature fluctuations, increases the humidity and increases the formation of dew. Since the forest climate is characterized by the lower solar radiation and the higher air humidity, the air temperatures in summer are usually lower there than outdoors. There may be differences of 3 ° to 6 ° C compared to the open air and 4 ° to 8 ° C compared to cities. Large contiguous forest areas near cities have a positive effect on the climate. The temperature differences between the forest and the city cause a constant exchange of air. At the same time, leaf organs filter dust, soot and gaseous contaminants out of the air, so that as a result cool and purified air flows back into the settlement. The forest also protects neighboring areas from the harmful effects of wind and frost.

2.4 Immission control
The forest filters dust, gases and radioactive substances from the air. The filter effect of forests is particularly dependent on the leaf surface. One hectare (10,000 m2) Spruce forest filter out 420 kg of dirt particles; a beech forest of the same size, bare in winter, but only 240 kg of dirt particles. Gases can mainly be absorbed when the treetops are damp and the gases can dissolve in the rainwater (acid rain). Our forests filter up to 50 tons of soot and dust from the atmosphere per hectare every year.

2.5 Oxygen production / CO2-Consumption
Trees produce oxygen as a "waste material" during photosynthesis. Part of it is used up again during breathing at night. Oxygen production and consumption of carbon dioxide (CO2) of a tree depends on many factors: age, climate, length of the growing season, etc.

Some numbers on the subject of oxygen and CO2 clarify the meaning of the trees:

  • a 100 year old beech tree produces 4,600 kg of oxygen every year. An adult can breathe from this for more than 13 years [source: Holzabsatzfonds]
  • Each hectare of forest binds around 10 t of CO annually2[Source: Bavarian Ministry of Agriculture 2007]
  • 1,851 kg of CO are required to build one ton of wood2 and 1,082 kg H2O necessary. In addition to the ton of wood, this produces 541 kg of clean H2O and 1,392 kg O2. [Source: "Everything about wood" 75 questions, 75 answers, from the Bavarian Forest Administration]
  • A 100-year-old spruce has up to 1.8 t CO in the atmosphere2 withdrawn [source: German forestry. Facts and figures. Publisher: Holzabsatzfonds]
  • 1.2 billion t of carbon are stored in the aboveground and underground biomass in German forests. [Source: inventory study 2008]
  • The entire CO2- Germany's emissions are 830 million t per year. Tree growth in Germany neutralizes 222 million t per year. [Source: Johann Heinrich von Thünen Institute]

3. Recreational function

The forest has also played a prominent role in German society since the Romantic era for recreation and leisure. It offers attractive excursion destinations with a balanced local climate, tranquility and diverse forest landscapes. The forest is a much-visited area for exercise and relaxation and is of great importance for the health and productivity of the population.

The stressed Central European not only recuperates subjectively through the peace and quiet of the forest, but also objectively provides convincing data: 99% fewer dust particles and air enriched with essential oils regenerates the lungs. The protection from intense sunlight and the higher air humidity are also perceived as pleasant. In addition, it is usually 2 - 3 ° C colder in the forest in summer, making it a great place to relax against the heat.

4. Educational function:
The forest offers an ideal place to illustrate the concept of sustainability. For over 200 years it has been possible to preserve the forest in its current form by applying the concept of sustainability (only as much wood is removed as it grows back). Every action in the forest has an impact on future generations. On this basis, the SDW continues to develop its forest pedagogical concept.