Trees absorb carbon from the air and store it in the wood over a long period of time. Only when the wood decays or burns is the carbon released back into the atmosphere. The forests of North Rhine-Westphalia store around 880 million tonnes of carbon dioxide (CO2) (as of 2010). This forest storehouse increases by 4 million tonnes of CO² every year. In addition, carbon is trapped in the forest soil.
Forests become carbon sinks when the absorption of CO² from the air is greater than the release. Especially young trees that grow rapidly, contribute to this. In natural forests there is a balance between carbon sequestration and release, so that the total amount of stored carbon remains the same. In managed forests, on the other hand, the wood does not rot but is further processed. The CO² remains stored in the wood far beyond the lifetime of the tree. There is an additional effect when wood replaces other materials that require a lot of energy for their production: this prevents the emission of additional greenhouse gases that would result from the use of fossil fuels like oil and coal.
Even when wood burns, the tree only releases as much carbon as it has absorbed from the air. Cascade utilisation is particularly climate-friendly: i.e. the wood is first processed into a durable product and only after further stages of use is it used and burnt to generate energy.
Climate change in the forest
The climate in North Rhine-Westphalia has already changed. It has become warmer and wetter. There are more hot summer days with temperatures above 25°C and fewer frost days with temperatures below 0°C than in the past. In addition, extreme weather occurrences are more frequent. The risk of severe storms or prolonged drought and forest fires is increasing. The forest floor has also been affected. In warmer soils, degradation processes take place more quickly, thereby releasing more nutrients. When it rains these nutrients are washed away so that they are no longer available to the trees.
The climate also changes the flora and fauna. Heat-loving species migrate. In addition, some species of pests reproduce rapidly due to the milder climate and the increased opportunities for reproduction as a result of weakened trees.
It is very difficult to predict exactly how climate change affects a particular forest location. Foresters use simulations to decide how best to prepare forests for the climate in the future. That said, there are many uncertain factors because the interactions of animal and plant species in the forest are highly complex.
Different species of tree place different demands on the soil, moisture and nutrient supply. Each location must be examined to see whether the existing tree species will be able to cope in the future, or whether they should gradually be replaced by other species. As a matter of principle, forestry relies on near-natural mixed forests with a great variety of species because these are more resistant than pure monocultures.
Beech trees can adapt relatively well to changing environmental influences. But in the future they will not be able to survive in locations that are too dry or too wet. However, when temperatures rise, they can create new habitats in low mountain ranges.
Spruce trees are sensitive to drought. If there is no rain, the weakened trees are more susceptible to storm damage and insect infestation. In the coming years, their numbers will decline drastically.
Red oaks are not native to this area, but are considered suitable for their location. Since the beginning of the 20th century they have been planted as an alternative to oak and beech trees. In forests with FSC and Naturland certification, their share is not allowed to exceed 20%.