Study shows: pesticides spread in an Alpine Valley from the valley to the summit region

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The study region, the Venosta Valley, is located in the west of South Tyrol, the largest contiguous apple-growing region in Europe. South Tyrolean apples are known for their perfect appearance, which often goes hand in hand with the use of large quantities of pesticides during production. A new study by the RPTU University of Kaiserslautern-Landau and the University of Natural Resources and Life Sciences, Vienna (BOKU) shows that these pesticides do not remain on the cultivation area, but can be detected throughout the valley and up to high altitudes. The pesticide mixtures detected can have harmful effects on the environment.

The Venosta Valley is located in South Tyrol, which is primarily associated with mountains and nature. In this region in the North of Italy, more than 7,000 apple growers produce ten percent of all European apples. Conventional apple cultivation relies primarily on synthetic pesticides, which are applied by fan assisted sprayers: insecticides to combat pests such as the codling moth and fungicides against fungal diseases that cause scab on the fruit. This results in a high level of drift into the environment, especially in windy conditions.

For a long time, even experts assumed that the synthetic pesticides essentially remained in the apple orchard where they were applied and could only be found in the immediate vicinity. However, this assumption is based on outdated and less sensitive measurement methods and the fact that pesticides away from the production areas were simply not recorded, explains environmental scientist Carsten Brühl from the RPTU in Landau. With today's modern analytical methods, up to one hundred pesticides can be measured simultaneously, even in low concentrations. In fact, studies show that pesticides spread well beyond agricultural land and affect insects in nature reserves (Brühl et al 2022, Scientific Reports) or can be found in the ambient air far away from agriculture (Zaller et al. 2022, Science of the Total Environment). In the Venosta Valley, a decline in butterflies on mountain meadows was observed several years ago. Experts suspected a connection with the use of pesticides in the valley, but there are hardly any studies on the question of how far current pesticides are actually transported and how long they remain in the soil and plants. This prompted Brühl and his colleague Johann Zaller from BOKU to investigate the distribution of pesticides in the environment in the Venosta Valley.

Measuring pesticide distribution on a landscape scale for the first time

"From an ecotoxicological perspective, the Venosta Valley is particularly interesting, as the valley is characterised by highly intensive cultivation with many pesticides and the mountains are home to sensitive alpine ecosystems, that are in some cases also strictly protected," explains Brühl. Together with his team and colleagues from BOKU and South Tyrol, he has analysed pesticide contamination at landscape level - along the entire valley up to high altitudes. Systematically recording and visualising the fate of pesticides on such a large scale is a first in environmental science. For their study, the researchers established a total of eleven so-called altitudinal transects along the entire valley axis, stretches that extend from the valley floor at 500 metres above sea level to the mountain peaks above 2,300 metres. The team took samples every 300 metres along these altitudinal transects. Plant material was collected and soil samples taken at a total of 53 locations.

The subsequent analysis showed that although the pesticides decrease overall at higher altitudes and with distance from the apple orchards, the researchers still detected several substances in mixtures in the soil and vegetation, even in the upper Venosta Valley with hardly any apple cultivation.  "We found the substances in remote mountain valleys, on the peaks and in national parks. They have no place there," emphasises Brühl. Due to the sometimes strong valley winds and the thermal updrafts in the Venosta Valley, the substances spread further than one might assume based on their chemical and physical properties. Even at the low concentrations measured, pesticides can lead to sublethal effects on organisms. For butterflies, for example, this could mean a reduction in egg laying, which then leads to a population reduction. There was only one place where the researchers found no pesticide substances in the vegetation - interestingly, there are also a lot of butterflies in that place.

Almost 30 pesticides detected

The researchers found a total of 27 different pesticides in the environment, but at the same time emphasise that they carried out their measurements at the beginning of May and that further products are used during the growing season up to the harvest. On average, almost 40 applications of pesticides are common during the season. This means that more complex mixtures with several substances and recurring higher concentrations are likely. In almost half of all soil and plant samples, the researchers were able to measure the insecticide methoxyfenozide, which has no longer been authorised in Germany since 2016 due to its harmfulness to the environment. Little is known about how chronic exposure to pesticides with mixtures in low concentrations affects the environment, and about the possible interaction of different substances. In the environmental risk assessment as part of the European authorisation procedure, mixtures are not evaluated, but the substances are considered individually. "This has nothing to do with the reality of applications in the field or in the orchard and their fate in the environment," says Brühl.

The researchers are concerned about how widespread the pesticide contamination was in the soil and plants and that even national parks, which were actually set up to protect endangered plants and animals, are exposed. "The concentrations we found were not high, but it has been proven that pesticides affect soil life even at very low concentrations," explains soil expert Johann Zaller from BOKU. In addition, the team always found a cocktail of different pesticides, the effects of which may be amplified. "The results also show that the technique of pesticide application in apple cultivation is in great need of improvement, otherwise so many pesticides would not be found away from the apple orchards," Zaller is convinced. It is also uneconomical if the pesticides are not applied specifically to the target organisms.

"We know from previous studies (Caroline Linhart et al 2021, Environmental Sciences Europe) that children's playgrounds near apple orchards are contaminated with pesticides. In some cases even throughout the year," says co-author and pesticide critic Koen Hertoge, who lives in the Venosta Valley. "The current results show a new dimension to the problem, as even remote areas are contaminated with pesticides. Measures to protect nature and the health of the population are absolutely necessary and the new provincial government is now called upon to act."

Promoting functional biodiversity as an alternative to pesticide use

Possible measures would be to reduce or even ban the use of pesticides, at least the substances detected in remote areas, the researchers conclude from their findings. In return, it is important to promote management practices that also encourage beneficial insect-pest interactions, the so-called functional biodiversity in the apple orchard and in the surrounding area. This means, for example, semi-natural and flower-rich grasslands that are distributed across the landscape and provide a habitat for the antagonists of apple pests. In addition, systematic monitoring should be introduced that includes measurements at various locations throughout the year in order to estimate the year-round pesticide input.

According to the researchers, the responsibility for reducing the use of pesticides lies not only with the apple growers, but also with the large supermarket chains: they could promote the acceptance of apples that do not look quite so perfect. This is quite realistic. The fact that people is also critical of the use of pesticides was demonstrated in 2014 by a referendum in the market town of Malles/Mals in the Upper Venosta Valley, where the majority voted against conventional apple cultivation.

Carsten Brühl concludes from the observed spread throughout the landscape: "We need regions where plants and animals are not contaminated with these bioactive substances. A reduction in pesticides - including large areas without the use of any synthetic pesticide - and the simultaneous expansion of organic farming is urgently needed to reduce landscape pollution. Our results show that it is urgent to act now, unfortunately we have no more time."

The study:

Carsten A. Brühl, Nina Engelhard, Nikita Bakanov, Jakob Wolfram, Koen Hertoge, Johann G. Zaller. 2024. Widespread contamination of soils and vegetation with Current Use Pesticide residues along altitudinal gradients in a European Alpine valley. Nature Communications Earth & Environment.
https://doi.org/10.1038/s43247-024-01220-1

Further studies mentioned:

Carsten A. Brühl, Nikita Bakanov, Sebastian Köthe, Lisa Eichler, Martin Sorg, Thomas Hörren, Roland Mühlethaler, Gotthard Meinel, Gerlind U.C. Lehmann. Direct pesticide exposure of insects in nature conservation areas in Germany. Scientific Reports. https://doi.org/10.1038/s41598-021-03366-w

Johann G. Zaller, Maren Kruse-Paß, Ulrich Schlechtriemen, Edith Gruber, Maria Peer, Imran Nadeem, Herbert Formayer, Hans-Peter Hutter, Lukas Landler. Pesticides in ambient air, influenced by surrounding land use and weather, pose a potential threat to biodiversity and humans. Science of The Total Environment. https://doi.org/10.1016/j.scitotenv.2022.156012

Caroline Linhart, Simona Panzacchi, Fiorella Belpoggi, Peter Clausing, Johann G. Zaller, Koen Hertoge. Year-round pesticide contamination of public sites near intensively managed agricultural areas in South Tyrol. Environmental Sciences Europe. https://doi.org/10.1186/s12302-020-00446-y

Contact:

Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau (RPTU)
Prof. Dr. Carsten Brühl
iES Landau, Institut für Umweltwissenschaften
+49 (0)6341 280-31310
carsten.bruehl@rptu.de

Universität für Bodenkultur Wien (BOKU)
Prof.  Dr. Johann Zaller
Institut für Zoologie
+43 1 47654-83318
johann.zaller@boku.ac.at

Koen Hertoge
+39 345 816 05 16
koen.hertoge@gmail.com

Press Contact:

Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau (RPTU)
Kerstin Theilmann
+49 6341 280-32219
kerstin.theilmann@rptu.de

Universität für Bodenkultur Wien (BOKU)
Bettina Fernsebner-Kokert
+43 (0) 664 885 86 531
bettina.fernsebner@boku.ac.at