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Jülich Expertise for COP 25

Interview with agrosphere researcher Prof. Harry Vereecken

Jülich, 29 November 2019 – “Es Tiempo de Actuar” – “It’s time to act”: That is the tagline of this year’s UN Climate Change Conference (COP 25) beginning on Monday in Madrid. Jülich atmosphere and agrosphere researchers are contributing from a scientific perspective to a better understanding of the multitude of interactions between human activities and the climate. This series of interviews introduces research topics and experts at Jülich associated with COP 25.

Not once since weather records began has Germany had as much sunshine and as little precipitation as in 2018. The extreme drought led to considerable crop failures, above-average numbers of forest fires, and historically low water levels in rivers and lakes. The following year, 2019, also saw some extremely hot temperatures, with some new local records. Scientists from Jülich’s subinstitute for agrosphere research are investigating the long-term effects of this on soils and the climate. Read our interview with Prof. Harry Vereecken, director at the subinstitute.

Prof. Harry VereeckenProf. Harry Vereecken
Copyright: Forschungszentrum Jülich / Ralf-Uwe Limbach

After the drought-stricken summer of 2018, what can agrosphere researchers say one year on about how the drought has affected the soil and therefore the vegetation?
The investigations conducted within the TERENO network show that forests in certain regions do not store as much carbon dioxide any more. This can unambiguously be attributed to the drought in the summer of 2018. In NRW, the loss of CO2 storage capacity in the affected areas amounts to 10–15 %.

Where do the data for these investigations come from?
In addition to TERENO, we have ICOS as a source. ICOS is a project for which measurements of the carbon cycle, emissions, and the atmospheric concentration of greenhouse gases are made available.

Were the soils able to recover in 2019?
No, unfortunately not. During 2019, the soils were also consistently drier than on average. In spite of the rainfalls, the soils’ capacity for storing water is not yet back to normal levels. We can verify this using model calculations and simulations. We need more precipitation! The question is what long-term effects the soils’ continued dryness will have on the forests, which were already suffering from drought stress in 2018.

Another case of “Waldsterben”?
No, it’s no forest dieback, but the tree population will change. We can’t say yet which kinds of trees this will affect. This forest changeover takes its time – time during which not as much carbon dioxide may be stored. We observe this on our test site in Wüstebach in the Eifel within the scope of the removal of spruces. The dryness last year was another setback: the forest system now needs even longer to reach point zero, i.e. the balance between CO2 absorption and emission.

The drought of the past two years means that regionally, farmers are facing massive challenges. What options are there to adapt to the situation?
Agriculture has two options. One option is to change over to plants that can handle drought stress, for example cereals such as barley. The other option – and this will become a topic of discussion – is irrigation. In northern Germany, where sandier soils prevail, irrigation is already increasingly needed. In our region, we have soils that can store water very well. And still, we are already seeing smaller yields. The questions are how fast farmers can react and whether they have access to groundwater.

Jülich agrosphere researchers are working with farmers within the ADAPTER project. What is this project all about?
The aim of ADAPTER is to improve predictions of soil moisture through cooperation with farmers. We provide them with simple sensors that measure soil moisture on their fields. We receive the data for our model calculations and can thus make more accurate predictions. Our model can visualize how soil moisture will develop down to each plot of land. The farmers can then use these results to decide when to irrigate.

Soils are important CO2 stores. What strategies are there to maintain or even boost this ability?
Humus is an important CO2 store, so the existing humus in the soil must be maintained or its proportion even increased. This can be done through organic farming and planting forest strips on fields with hedges and fruit trees.

So what does this mean for soil management?
Fallow fields emit more CO2 than planted ones. It therefore makes sense to reduce the amount of fallow ground, for example by sowing catch crops. Ploughing also releases CO2, so the question must be asked whether soil should be ploughed at all, and if so, how intensely. Another option is grassland, which stores more CO2 than farmland.

Marshland must be better protected because it stores a lot of CO2. When marshland is drained, for example for peat mining, the CO2 is released back into the atmosphere.

Further information:
Institute of Bio- and Geosciences – Agrosphere (IBG-3)
ADAPTER (in German)
Jülich experts on climate research (in German)

Further interviews on the world climate conference in Madrid
Part 2 of the interview series with Prof. Martin Riese, Dr. Jens-Uwe Grooß, and Dr. Peter Preusse on the climate campaign SouthTRAC (in German)

Prof. Harry Vereecken
Institute of Bio- and Geosciences – Agrosphere (IBG-3)
Tel: 02461 61-4570

Press contact:
Erhard Zeiss
Press officer
Tel: 02461 61-1841