display
Terms such as “acid rain” or “forest dieback” originate from the 1970s, but are still highly topical issues and are still part of the everyday problems of Central European foresters in the 20s of the 21st century.
In the 1970s in western Central Europe and up to the early 1990s in Eastern Europe abundant sulfur oxides from industrial chimneys, which turned into sulfuric acid in the air and later fell back on the earth as acid rain, are now replacing nitrogen -Compounds from manure from factory farming and exhaust gases from road traffic are emissions that over time also make the soil more acidic. And indeed, after the forest dieback of the 1970s, which had just been averted, forestry scientists also see huge problems in the forests of the 21st century.
Acids from the rain also penetrate the soil.
There are naturally very different types of acidic and basic soils in which plants take root that have long since adapted to these conditions.
But if the precipitation changes this acid value, the conditions in the soil also shift.
display
As a result, the roots can absorb calcium, potassium, magnesium, sodium, manganese and aluminum, for example, better or worse than before.
Plants absolutely need a number of these elements to live, while others, such as aluminum, are poisonous.
The acid rain changes the previously good adaptation and can weaken and damage plants.
If climate extremes such as persistent droughts are added, even mighty trees can experience significant problems and even die over the years.
Measures were taken as early as the 1970s to prevent forest dieback.
Since then, filters have been capturing the sulfur and nitrogen compounds from the exhaust gases of the industry and thus removing the basis of the acid rain and the acidification of the soil.
Success was quickly achieved: Soils became less acidic and the content of important nutrients rose significantly again.
At the same time the aluminum concentration, which is dangerous for the roots, decreased.
Oaks should give way
In addition, particularly sensitive forest soils in western Germany, in the Thuringian Forest and in the Ore Mountains, have been sprinkled with finely ground dolomite rock since the 1980s.
This lime neutralizes acid and also contains the valuable nutrients calcium and magnesium.
The success was impressive: the acidification of the soils decreased significantly more on the limed areas than on the untreated soils, and the available nutrients increased more rapidly on the limed soils.
display
As a result, microorganisms, earthworms, millipedes and woodlice have been significantly more active since then and quickly digest plant residues in the top layer. However, around half of these consist of carbon, which in this way gets from the humus layer into the soil below. But there the carbon stays for a long time and no longer turns into carbon dioxide, which as a greenhouse gas heats up the climate.
Unfortunately, this liming only treats the symptoms, not the causes of soil acidification. Since the beginning of the 21st century, meadows and fields overfertilized with manure have been increasingly emitting nitrogen compounds, which then trickle back onto the forest floor as nitric acid with the rain, where they become nitrate. In addition, there are nitrogen oxides from the exhausts of the growing fleet of cars and trucks, which in the end also end up in the forest floor as nitric acid and nitrate.
The lime still works against these acids.
But nitrate also acts as a fertilizer.
This means that the trees grow faster at first.
Soon, however, other important nutrients such as phosphorus will be missing.
As a result, the quality of the wood decreases, but the forest damage increases again.
Once again, the problem must be tackled at the root: car traffic is allowed to blow less nitrogen into the air, and the manure problem must also be tackled.
Paradoxical funding policy of the EU
display
The forest would not be off the hook with these measures alone. There are forests on many areas that are anything but natural. In many places, the naturally occurring beeches were pushed back centuries ago and oaks were promoted instead, which provided better and more valuable timber. In such oak-dominated forests, however, pests such as the warmth-loving gypsy moth and oak processionary moth have an easy time of climate change. In the forest of the future, there shouldn't be large oak stocks, but there should be individual oaks. Beeches are better able to withstand the droughts, which are becoming more frequent due to climate change, because their deep roots can better reach the water in the deeper layers of the forest floor even in dry summers.
Another problem tree is the spruce, which was planted in many places in the 19th and 20th centuries. These trees grow faster and can be harvested and monetized much earlier than hardwoods. So you made money faster with spruce forests than with oak or beech. But when the climate changes, the storms often blow stronger. With their deep roots, beeches and oaks have much less problems with this than spruce, whose flat roots the trees can hardly hold on to in gusts of wind. More violent storms simply knock down many spruce forests.
On top of that, these conifers come from the cool north and have bad prospects in any case in warmer summers. For some years now, forward-looking foresters have allowed beeches and hornbeams, oaks and silver firs, cherries and alders, maples and ash trees to grow together in Central Europe. The forests of the past looked very similar.
Such forests fit perfectly into the concept of the European Union, which wants to become climate neutral by 2050 and relies on the support of forests that fish carbon dioxide out of the air and thus slow down climate change. However, evaluations of satellite images show that significantly more areas have been cleared since 2016 and much more wood has been removed from the forests than before. The European Union is promoting this process as well, as wood is considered climate-neutral because when it is burned, no more carbon dioxide is released than the tree fished out of the air when it was growing.
In principle this is correct, but only if you think in terms of very long periods of time.
Otherwise it's a milkmaid bill.
"If a beech forest grows for 120 years and its wood is then burned, the carbon dioxide stored during this time is suddenly released into the air," explains forest ecologist and nature conservation professor Pierre Ibisch from the Eberswalde University for Sustainable Development.
So it takes exactly these 120 years until the next beech forest has offset the climate balance.
And even if the wood is processed into furniture, it remains a milkmaid bill, because nowadays many pieces of furniture are often replaced after a few years and its wood is then burned.
Nature is the best gardener
With the promotion of firewood, the EU is messing up its own climate targets, which it can only achieve with the help of forests, which are currently growing to around 38 percent of the EU's area. After all, trees swallow around ten percent of the greenhouse gases that are blown into the air when EU citizens run their business. But that works out worse and worse when the forest area decreases, especially in countries like Sweden, Finland, the three Baltic states and Poland.
Forest fires, which are also raging more often in Central Europe because drought summers are increasing due to climate change, have the same effect.
In the city forest of Treuenbrietzen in Brandenburg, around 400 hectares of forest were on fire in the hot summer of 2018, and three villages had to be evacuated.
Then private forest owners removed the wood from their areas - and planted pines again.
Around three quarters of the small trees did not survive the next summer of drought in 2019, so the owners had put a lot of money into the sands of the Brandenburg region.
display
The situation is quite different on a 28 hectare section of the area. Here, Pierre Ibisch and his colleagues have let nature take its course since then. There, between black-charred pine trunks on the gray-black ash layer, innumerable quivering poplars, birches and willows were soon sprouting, their feather-light seeds being carried there by the wind.
One or the other beech and oak are now growing there, because jays often haul beechnuts and acorns far through the air. Since the burnt pines and their branches provide shade and cool these areas, less water evaporated there in the dry summers of 2019 and 2020, and the seedlings survived the periods of drought surprisingly well. Some of these trees are now even more than two meters high, provide shade for their part, retain more moisture and prepare the ground for a later mixed forest. And that should have a good chance even in the age of climate change.