Sekėjai

Ieškoti šiame dienoraštyje

2022 m. spalio 3 d., pirmadienis

Erosion pulls the ground out from under our feet

 "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.