"By VANESSA HENKES
Image: Markus Spiske
October 2nd, 2022 · Agriculture is deeply anchored in German
history. Forests became fields, in the Middle Ages three-field farming was
introduced, and over the centuries both methods and machines improved. But the
intensive cultivation is taking its toll on the soil.
Nutrition and German culture are shaped by agricultural
products. A large variety of cereals gives us around 3200 different types of
freshly baked bread every day. Potatoes and other vegetables enrich our table.
The cultivation of animal feed for cattle, pigs and chickens satisfies the
hunger for meat and eggs: in 2019/2020, the German population was able to consume
88 percent of the food grown in the country.
We owe vital products, but also dispensable consumer goods
such as beer or wine, to an important resource: the soil. If it is healthy,
rich in nutrients, farmers can produce high-quality crops. But meanwhile it
happens more and more often that the soil is sick.
Erosion increases, wind and water carry away the fertile
soil. What remains is barren land that is lost for cultivation.
In the so-called reptation, the wind moves sand or gravel.
The fine granules and small stones are pushed or rolled across the ground.
If the wind speed is higher, the so-called salation takes
place. Then sand and finer soil components such as silt are transported to a
height of up to fifty centimeters by jumping.
With the suspension, silt can be transported to even greater
heights, sometimes over several hundred kilometers. A typical example of this
is the "Saharan sand", which regularly causes "blood rain"
in Germany as well: silt is transported from the Sahara at high altitudes to
Central Europe. When it rains, it is "washed" out of the air.
Reptation accounts for 7 to 25 percent of wind erosion, 50
to 80 percent to saltation, and 3 to 38 percent to suspension.
Two processes take place during water erosion: First, in
heavy rain, for example, drops hit the surface of the ground, and small parts
of the soil are thrown up. If they fall back to the ground, they can clog its
pores. The area is closed, experts call it "slurrying". If the rain
continues, the water cannot seep away. It runs off over the muddy surface,
taking fertile soil with it.
Depending on how heavily it rains, how the soil has been
tilled and how steep the slope is, water erosion occurs either in areas or in
lines. With channel erosion, soil material flows off the field in small
grooves; with heavier precipitation and greater gradients, deep ditches can
also form, and several soil horizons can be eroded in the process.
As a result of heavy rainfall, large amounts of earth can
also be washed away. Not only fertile topsoil is then lost, but often even
entire hillside areas.
The danger of the wind
Not all regions of Germany are equally at risk from wind
erosion. The soil composition is crucial.
Federal states with sandy soils are particularly at risk.
Our map shows which regions of Germany will be particularly
affected in the future.
Drifts of organic matter, the decrease in the water capacity
of the topsoil and the general deterioration of the soil structure are just
some of the effects that wind erosion can have on fertile farmland. The plant
world is also severely affected in some cases, because pathogens sometimes
cling to the blown particles, and wind abrasion also damages the plants.
In the short and medium term, wind erosion also has the
effect that loose soil material is carried into sensitive ecosystems.
Wind erosion can accumulate substances that are difficult to
degrade in water bodies, causing lakes and rivers to eutrophicate and throwing
the ecosystem out of balance.
Wind erosion can also become a problem for people's health:
respiratory diseases are on the increase.
The danger of the water
Water erosion on agricultural land can have serious
consequences for nearby ecosystems. If the topsoil is removed from a larger
area, not only the most fertile layer of the soil is lost - which reduces the
yields. However, plants are also uprooted, covered or even destroyed. If a
heavy rain event occurs shortly after sowing or fertilizing, seeds or
fertilizer will be washed away and can be deposited in unwanted places. Water
erosion can result in muddy roads and dangerous landslides. Such landslides can
be very dangerous for infrastructure and people.
Wind erosion is a particular danger for the regions in
north-eastern Germany. Water erosion, due to the greater gradient of the
landscape, in the south of the republic.
Germany is already losing an average of between 23.3 and
53.1 million tons of soil every year through erosion. Under normal conditions,
it takes 100 to 300 years to develop a one centimeter thick layer of humic
soil, which can be lost in a single thunderstorm.
So erosion is not a problem of the future, but a problem of
the present.
The global erosion has direct consequences, also for Germany: In
Germany, around 11.5 million tons of grain had to be imported in 2021.
How could it come to this?
In search of the causes
By VANESSA HENKES
Image: Max Boettinger
Wind erosion
The decades of intensive use of the fields and climate
change are contributing to accelerated soil erosion. Soil moisture is a
particularly important factor. If the ground is too dry, it is possible for
particles to be carried far away even at wind speeds of four to six meters per
second - which the German Weather Service describes as a "weak
breeze".
However, the soil has tended to become drier in recent years: while in 2002, for example, soil moisture recovered again and again
after a long absence of rain, it simply decreased in 2018. The soil was so dry
that the so-called hydraulic conductivity had already changed - and recovery
was becoming more difficult: the water was only able to seep through slowly,
and even downpours brought hardly any moisture into the soil.
It is not yet known where and when wind erosion occurs in
Europe and how severely it threatens agricultural productivity. The European
Soil Data Centre, ESDAC for short, has therefore proposed mapping the soil's
susceptibility to wind erosion.
Water erosion
Whether water can severely erode the soil depends on
gradient, slope cultivation and above all on the duration and severity of
precipitation. One speaks of a heavy rain event when 15 to 25 liters of rain
per square meter fall within one hour, then the weather service also issues a
“distinctive weather warning”. Such events have become more frequent in recent
years; For example, heavy rain lasting an hour or two was five times more
frequent in 2018 compared to 2001. The number of heavy rain events has more
than doubled since 2001.
However, the fluctuations are very strong, which has to do
with the average temperatures over the years: If it is warm for a long time,
the air can absorb more water. As a result, there is more water vapor in the
atmosphere, which in turn leads to more precipitation.
It is always difficult to link individual extreme weather
events to climate change, but the frequency of events is viewed by researchers
as a strong indication of this.
In the case of water erosion, the so-called K-factor
indicates how vulnerable the soil is to erosion. The sandy soils of the north
are only partially affected by water erosion. In low mountain ranges and the
Alps, the K-factor is significantly higher.
The way in which the land is cultivated sometimes directly
leads to soil erosion, such as deep plowing of the field.
In order to slow down erosion by wind and water, farmers and
institutions such as the Leibniz Center for Agricultural Landscape Research or
Agriculture and Agrifood Canada are trying to develop and implement concrete
packages of measures.
Can the floor still be saved?
By VANESSA HENKES
Image: Maksym Kaharlytskyi
What needs to be done and who needs to take care of it?
Depending on how the soil is, its cultivation should be
adjusted. Farmers can do a lot to ensure that the soil is preserved for a long
time. However, says Sheng Li of Agriculture and Agrifood Canada, there is no
single measure that is the only true one. In most cases, compromises are
necessary in order to maximize soil protection overall. You also have to
develop integrated systems.
Many soils have been used for arable land for centuries and
are therefore already so badly eroded that, even if there were no further soil
erosion, it would take decades for them to recover.
However, a kind of aftercare can, for example, increase the
carbon content of the soil, reduce compaction and improve the soil's ability to
store nutrients.
An important question in the restructuring of soil
management is that of responsibility: who must act? Soil scientist Katharina
Helming and her colleague Roger Funk from the Leibniz Center for Agricultural
Landscape Research in Müncheberg, Brandenburg, find that the previous
agricultural policy in Germany was "on the whole not beneficial" for the
soil. Instead, they set incentives to further increase erosion. Katharina
Helming sees politics as having a duty to set an example and price
environmental costs into the products, for example.
However, everyone can also contribute with their consumer
behavior to ensure that the soil is preserved. Researchers try to work directly
with consumers and develop labels. However, the problem here is that there are
already too many of them and consumers are confused.
Soil protection also goes hand in hand with less meat
consumption. Animal husbandry has a massive impact on areas that are sometimes
not actually available. It is not possible to farm in a way that promotes soil
and not to change consumer behavior. Feeding the growing world population while
at the same time declining yields per area is hardly possible without
renouncing meat.
However, according to Roger Funk, it is also not helpful to
demonize animal husbandry as a whole. Because without animal husbandry there is
less organic fertilizer, which is extremely important for the preparation of
the soil, as this is the only way for the nutrients to get back into the soil
layers.
Politicians and the public have only recently started to
take notice of soil: the situation is serious. For this reason, soil scientists
and agricultural engineers would like to see a different policy that would
ensure, for example, that the additional costs for storing and cleaning water
and maintaining species-rich habitats are passed on to consumers in the price.
Research must also be continued in order to better understand the processes of
erosion and their consequences. This is the only way to stop it - and protect
the ground."
The Russians sold us, including the Germans, very cheap
energy and energy-intensive fertilizers. As a result, our intensive farming
could thrive even though that fertilizer kept leaching from the eroded soil.
Now this fairy tale is over. We need to learn to farm as intelligently as our
ancestors did and without cheap Russian energy.
Modern farming also contributes a lot to global warming,
with dire consequences for agriculture itself.
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