The study ‘Widespread contamination of soils and vegetation with current use pesticide residues along altitudinal gradients in a European Alpine valley‘ demonstrates the extraordinary breadth of the so-called ‘drift effect’ of pesticides, from the largest apple orchard in Europe in Val Venosta to the mountain peaks above it. (1)
1) Pesticides, the effect comes
Pesticides are volatile substances, therefore capable of reaching locations far away from the sites where they are sprayed. Planetary agriculture consumes 3 million tons of pesticides every year which are deposited in the soil, percolating until they reach deep aquifers or the seas, through surface watercourses. (2)
The dispersion of pesticides in water has been extensively studied, as well as considered in the Water Framework Directive, but little is known about their spread in soil, vegetation and insects. The study in question (Brühl et al., 2024), published in Nature on 14 February 2024, therefore focused on two matrices:
– soils, where most solitary bees (about 65% of species) dig their nests, and
– vegetation, habitat and food resource for pollinating and herbivorous insects, from bees to grasshoppers and butterfly caterpillars.
2) Val Venosta, the study
The largest apple orchard in Europe – in the Val Venosta, Bolzano province, extending for 80 km with various differences in altitude – was chosen as a case study. Around 7000 farmers produce in this area – one of the Alpine landscapes that are richest in biodiversity, but also ecologically sensitive and protected – 10% of ‘Made in Europe’ apples. (3) And it was already known that the pesticides used in apple orchards had contaminated areas outside the crops, such as children’s playgrounds, but the extent of their distribution was not yet clear.
The analysis was limited to 97 current used pesticides (CUPs), based on soil and vegetation sampling in open, uncultivated habitats along 11 transects ranging from the valley floors adjacent to crops (517 m above sea level), to meadows above the tree line, at 2318 m altitude. In these 11 altitudinal transects, soil and vegetation were sampled in 53 sites (identified with the red dots on the map).
3) Results
27 CUPs – including 10 insecticides, 11 fungicides and 6 herbicides – were detected in the analyzed samples. In particular:
– 23 CUPs were found in the soil. 59% of the samples were contaminated, with a preponderance of the insecticide methoxyfenozide, detected in 21 out of 53 samples (40%), followed by the fungicide fluazinam with 13 detections (25%) and trifloxystrobin, with 8 detections (15%)
– 18 CUPs were found in the vegetation. All but one sample (98%) was contaminated with fluazinam and trifloxystrobin. Penconazole was found in 35 out of 53 samples (67%), methoxyfenozide in 24 out of 53 (45%).
The interviews among growers revealed that fungicides accounted for 50% of all applications, but insecticides were used in greater quantities (43% of the total active ingredients applied).
4) Distribution of pesticide residues
The number and concentrations of pesticides detected in the soil and vegetation vary in relation to various factors such as the distance from the orchards, the season and atmospheric events. The researchers thus found, for example, that:
- specific clusters of pesticide residues formed in the Upper and Lower Val Venosta but not in the Middle Val Venosta. This is explained by the fact that the apple trees in the Lower Val Venosta were beginning to bear fruit, in the Upper Val Venosta they were beginning to flower, and in the Middle Val Venosta they were in an intermediate stage of maturation
- the greatest residues are found in the sampling sites where the concentration of orchards within a 1 km radius is highest
- the downstream play areas, located within the apple growing area and a short distance from the orchards (20-90 metres), are contaminated by pesticides
- the number of pesticides detected decreases significantly with increasing altitude. However, some pesticides used in orchards, such as fluazinam, have also been detected at higher altitudes (2318 m) and in the remote Val Marzia. This phenomenon could be explained by the exchange of air masses and the exposure of mountain slopes. Low temperatures and high precipitation rates, for example, increase pesticide deposition in mountains
- the wind transports the pesticides homogeneously on the slopes with consequent deposition and contamination of the entire area, from the valley floor to the mountain tops, without significant differences between the slopes facing north and south.
The detection of CUPs in the soil and vegetation is not affected by the tree cover present around the sampling sites. Indeed, a greater concentration of pesticides on the ground has been observed as the trees trap the fog, which is capable of containing high concentrations of pesticides. The volatility of the substances does not appear to be significant, while they are expected to increase in the months following May.
5) Pesticides cocktail
The danger of pesticides and, therefore, the levels of tolerable residues are identified for the individual substances. Without considering the cumulative and synergistic toxic effects of mixes of different active ingredients, the so-called ‘cocktail effect’, although several studies have demonstrated its greater danger. (4)
In Val Venosta, researchers found that 26% of soil samples contained more than one pesticide, and 9% of samples had more than 5. For vegetation, the percentages go up. 98% of all samples had at least 2 CUPs and 28% contained 5 or more. Records of 12 different substances in the soil and 13 in the vegetation were achieved in the sampling sites located at the lowest levels of the Val Venosta.
The apple samples from Alto Adige also present multi-residual contamination with an average of 4,4 pesticides detected in 2021. Although no exceeding of the maximum application levels permitted by law was recorded, nor any exceeding of the maximum levels of the individual CUPs in apples, the detections of multiple CUPs residues are worrying because risk assessment procedures in Europe to date do not consider the possible adverse effects on human health and the environment of the pesticide mixture.
6) Unapproved pesticides
Fungicides azoxystrobin and fluopyram and the neonicotinoid insecticides thiacloprid are not approved in apple crops but have been detected in some soil and vegetation samples. The neonicotinoids imidacloprid and clothianidin, banned in the European Union since December 2020, were also detected. Perhaps due to their long degradation times.
4 of the 6 herbicides detected – flazasulfuron, metazachlor, metolachlor-s and napropamide – are not approved for use in apple orchards. The cause of their discovery, especially at lower altitudes, could perhaps be explained by their use in
other agricultural cultures or in private gardens.
7) Pesticides in protected areas
The drift effect also extends to protected areas. Many pesticides and their mixtures have in fact been detected in the soil and vegetation of the Stelvio National Park, around the Ortles-Cevedale mountain massif and in the Gruppo di Tessa Natural Park, Natura 2000 areas.
On all protected sites the fungicides fluazinam and trifloxystrobin were detected. In some samples, methoxyfenozide was also found, an insecticide that influences the moulting of insects in the larval stage and was therefore banned in Germany and Switzerland.
8) Researchers’ considerations
Pollution from pesticides in protected and conservation areas demonstrates, according to the researchers, that the measures taken by local authorities to control the drift effect are not sufficient. Furthermore, these data are underestimated, since the study analyzed the presence of only pesticides compared to the over 400 allowed in the European Union.
The research authors (Brühl et al., 2024) also underline how it is reductive to evaluate the effect of only one pesticide at a time, considering that the exposure of organisms to cocktails of pesticides even at low concentrations could cause synergistic effects at sub-lethal levels, leading to a decline in the population in long period.
9) Provisional conclusions
‘The results of this study highlight the need for changes in cultivation practices for Val Venosta, but also for other regions with pesticide-intensive agricultural production. The observed landscape-scale distribution of CUPs, the contamination of protected areas and the resulting exposure of biodiversity and humans could only be reduced through wider use of conservation measures. biological control of conservation and one general reduction, immediate and drastic change in the use and risks of pesticides, as outlined in the European Green Deal and the Montreal Convention on Biodiversity meeting for 2030′ (Brühl et al., 2024).
Alessandra Mei
Footnotes
(1) Carsten A. Brühl, Nina Engelhard, Nikita Bakanov, Jakob Wolfram, Koen Hertoge and Johann G. Zaller. Widespread contamination of soils and vegetation with current use pesticide residues along altitudinal gradients in a European Alpine valley. Commun Earth Environ 5, 72 (2024). https://doi.org/10.1038/s43247-024-01220-1
(2) Dario Dongo, Alessandra Mei. Dispersion of pesticides in soils, aquifers, surface waters and oceans. Research on ‘Nature’. GIFT (Great Italian Food Trade). 26.8.23
(3) Alessandra Mei. Apples to pesticides, the Val Venosta case. GIFT (Great Italian Food Trade). 21.3.23
(4) Marta Strinati. Pesticide cocktails cause toxicity, even at the doses allowed in the EU. New study. GIFT (Great Italian Food Trade). 24.10.20
Graduated in Law from the University of Bologna, she attended the Master in Food Law at the same University. You participate in the WIISE srl benefit team by dedicating yourself to European and international research and innovation projects.
