“Impervious sealing means total loss”
Christiane Weihe
Valuable soils develop over thousands of years. We destroy them in a fraction of that time. We cannot continue to treat soils like this, says Ricarda Miller. The agricultural engineer carries out soil surveys and soil function assessments, assists with construction projects and always keeps a firm eye on soil protection. We talked to her about the most significant pressures on soils, the possibilities for regeneration and awareness of soil protection.
Ms Miller, what do we actually know about the soil?
It varies. We know a lot about the physical and chemical processes and also about the different soil types. But we know very little about many of the soil organisms. Many species are still unexplored. Our knowledge is particularly limited when it comes to soil microorganisms and the interactions between soil, organisms and plants. Incidentally, we also do not know enough about how climate change affects our soils. Drought stress and higher soil dryness will of course also change these interrelationships.
Can soils recover?
Soils develop over thousands of years and can be destroyed very quickly. Many people do not realise just how sensitive soils are. Impervious sealing, for example, entails a total loss because the soils’ functions are destroyed when water and air can no longer penetrate. This is the case for 47 per cent of the soils that are newly converted every day for settlement, commerce and transport infrastructure.
Can soil be unsealed and thus made usable again?
Yes, that is possible and useful. It is possible to unseal soil and create soil space that plant roots can penetrate − but this requires soil experts. To achieve this, soil that has been excavated elsewhere is carefully spread. This allows for certain functions to be restored, such as the water regime or the cooling function. But you will never achieve the same value and functionality as with naturally grown soil. That is why we cannot continue to seal more and more soil surfaces.
So is impervious sealing the biggest problem for soils?
In Europe, yes. But there are many other problems and various types of soil degradation, such as compaction, salination or acidification. In some cases, farming also takes a heavy toll. And soil erosion − wind and water carrying away soil − is yet another problem.
Can anything be done about erosion?
Absolutely. Water can be stopped by erosion control strips and wind can be reduced at small scales, for example by hedges. In general, year-round soil cover is important, for example the cultivation of catch crops. These measures are long-term in their nature and will then also benefit the soil life, as they lead to improved nutrient turnover.
Are there ways to regenerate soils?
Yes, and they are already being implemented. In large-scale mining or extraction projects, such as for lignite or gravel, soils are recultivated, meaning that material is brought in from other sites and new soil is built up. Up to a certain limit, pollutant loads can also be removed and it is possible to remediate soils using plants that absorb heavy metals. In the case of severe compaction, plants can also help to increase soil pore volume again.
What is the level of awareness of soil protection in the farming sector?
In my experience, a large part of the farming sector sees the soil as worth preserving; it is their production base after all. And farmers know their soils very well. Nevertheless, soil conservation is not the top priority. Sometimes, however, the necessary knowledge is lacking, for example about the fact that planting a catch crop is worthwhile − but only after a few years. In my view, still nowhere near enough emphasis is placed on soil and water conservation in agricultural education. Yet it can be worthwhile to actually gear production towards these aspects, as many examples, including in the organic sector, have shown.
What are Germany’s states and municipalities doing for soil protection?
There are numerous lighthouse projects – small-scale but big-picture − and good examples, such as municipal soil protection strategies. Stuttgart, for example, is a real pioneer. At the turn of the millennium, the city recognised that it was running out of land and took countermeasures by setting land consumption quotas. There are currently about twenty cities in Germany that have a soil protection strategy, including Berlin.
Thank you for talking to eco@work.
The interviewer was Christiane Weihe.
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Talking to eco@work: Ricarda Miller, Head of the Lenggries Regional Office of Schnittstelle Boden