A recent study by the RPTU University Kaiserslautern-Landau shows extensive pesticide contamination in the landscape of the Upper Rhine Region. The research team led by Carsten Brühl shows for the first time that synthetic chemical pesticides from conventional agriculture do not remain on the cultivated areas, but spread from the lowlands to the Black Forest and the Palatinate Forest. The results show that the entire landscape is contaminated with pesticide mixtures, shedding new light on the potential environmental impacts of conventional agriculture. According to the researchers, pesticide use must be reduced urgently in order to protect areas around fields, orchards and vineyards.
The study, published in Communications Earth & Environment, covers the Upper Rhine Valley in Germany. The area, which extends for about 300 kilometers between Bingen and Basel, is a traditional agricultural landscape where, in addition to cereals, also vegetables, wine and fruit are grown due to favourable climatic conditions. Since the 1970s, synthetic chemical pesticides have been used extensively in conventional agriculture to control pests, weeds and fungal diseases. This often involves combining different active ingredients and multiple applications per year. As a consequence of these large-scale applications, so-called non-target areas – i.e. areas that are not directly sprayed, such as adjacent hedges, field margins, meadows or dry grasslands – are increasingly suffering from chronic pesticide contamination.
Environmental sampling over a 180-kilometer stretch
The research team carried out extensive sampling during the spraying season in June and July 2022: Along six 30-kilometer-long transects – defined measurement paths that ran from remote areas in the mountain ranges of the Palatinate Forest and the Black Forest to the Upper Rhine Valley – topsoil, vegetation, streams and puddles were sampled at 78 locations. The systematic recording and presentation of pesticides on such a large scale is a new approach developed at the Institute for Environmental Sciences in Landau. With the help of state-of-the-art analytical techniques that can detect even low concentrations, the study included 93 common pesticides.
Contamination from the lowlands to the highlands
The research team detected a total of 63 pesticides, and almost all of the measurement sites were contaminated. Residues were found in 97 percent of the soil and vegetation samples, often in complex mixtures of several active ingredients. According to the researchers, it is particularly worrying that even remote areas are not free of pesticides. The active ingredients were also detected several hundred meters from agricultural land. On average, five pesticides were measured in topsoil, with individual samples showing up to 26 different active ingredients. On average, the vegetation was contaminated with six pesticides, and in some cases with as many as 21 substances. "Our results are clear: pesticides spread far beyond fields. This is more than just an agricultural problem – it is a reality that affects us all. We can encounter pesticides while taking a walk, in playgrounds or in our own gardens," explains Ken Mauser, lead author of the study. People at particular risk include those with direct contact with pesticides, such as farmers themselves, as well as sensitive groups such as children, pregnant women and the elderly. Just recently, "parkinsons caused by pesticides" was recognized as an occupational disease in viticulture in Germany. One of the most frequently found pesticides was the fungicide fluopyram, which was detected in over 90 percent of all samples. Fluopyram is classified as a PFAS, a so-called "forever chemical", and the breakdown products can contaminate groundwater. According to the environmental scientists, the widespread distribution of the fungicide in the landscape seems extremely worrying due to its potential contamination of drinking water resources.
"Cocktail effect" danger from pesticide mixtures
The study shows that pesticides were often not found individually but rather as mixtures of multiple pesticides. A total of 140 different combinations of at least two active ingredients were detected. "Pesticide cocktails are particularly problematic because interactions can occur and effects can be amplified. In the current authorization procedure, each pesticide is assessed individually. This is not enough to grasp the complex risks of the realistic exposure to mixtures," emphasizes ecotoxicologist Carsten Brühl. "Colleagues from Heidelberg were able to show that pesticide mixtures in similar concentrations to those detected in this study reduce the egg laying of insects by over 50 percent in the laboratory. It can therefore be assumed that these mixtures definitely have an impact on the environment, especially if they are also present chronically, i.e. throughout the year, as we were able to show in another study."
Landscape modeling – pesticide dispersal and protected areas
A key component of the study was the modeling of pesticide contamination in the landscape. Using detailed geostatistical analyses, the researchers predicted the distribution of pesticide residues throughout the study area. The prediction maps show that the contamination extends beyond the sprayed areas and that even remote areas are not protected from pesticide contamination. According to the model, intensively used wine-growing regions such as the Southern Palatinate and the Kaiserstuhl are contaminated by 10 to 20 pesticides in the soil and vegetation. The areas outside the agricultural area, such as flower strips, hedges, adjacent grassland, but also designated nature reserves or national parks, are considered to be refuges for protected animal and plant species. However, the study shows that such areas in the agricultural landscape and even the remote mountain range of the Black Forest National Park or the Palatinate Forest-North Vosges UNESCO Biosphere Reserve are contaminated. A total of four different pesticides were detected in the Black Forest National Park, and three substances were also found on the Feldberg (1,494 meters a.s.l.). In their modeling, the researchers also made calculations for the "Kleine Kalmit", a nature conservation area near Landau in the Palatinate. Up to 15 different pesticides were predicted in the soil and vegetation – a finding that was confirmed by measurements of a previous study. Pesticide contamination thus not only endangers protected species, but also undermines efforts to protect biodiversity. "Protected areas near conventional agriculture show increased pesticide contamination. Sustainable and pesticide-free managed fields in adjacent areas could serve as a buffer zone and help to reduce the pesticide contamination of the reserves," explains Ken Mauser.
Pesticide reduction urgently needed
The study shows that pesticides do not only remain on agricultural land, but contaminate the entire landscape. In particular, the "cocktail effect" and the contamination of protected areas are worrying, according to the researchers. In view of their findings, the scientists call for a strict reduction in pesticide use to protect people and the environment, as well as monitoring of pesticide contamination in landscapes. This is also in line with the goals of the COP 15 United Nations Biodiversity Conference, which aims to halve global pesticide use by 2030. "Our approach of using landscape modeling to assess pesticide pollution can serve as a basis for future evaluations of the reduction efforts," notes Carsten Brühl.
In addition, large-scale pilot projects are needed to create pesticide-free cultural landscapes on a scale of 10 x 10 kilometers. According to the researchers, this is the only way to truly measure the positive effects of sustainable farming systems on biodiversity. Currently, pesticide-free agriculture, even when established in small areas, has no chance of realizing its potential in a landscape contaminated by pesticides. "Now it is up to politicians to develop and promote large-scale and effective pesticide-free approaches and to resolutely push ahead with the transformation to sustainable agriculture".
The study:
Ken M. Mauser, Jakob Wolfram, Jürg Spaak, Carolina Honert & Carsten A. Brühl 2025 Current-use pesticides in vegetation, topsoil and water reveal contaminated landscapes of the Upper Rhine Valley, Germany. Communications Earth & Environment. https://www.nature.com/articles/s43247-025-02118-2
Further study mentioned in the press release:
Carolina Honert, Ken Mauser, Ursel Jäger, Carsten A. Brühl. 2025. Exposure of insects to current use pesticide residues in soil and vegetation along spatial and temporal distribution in agricultural sites. Scientific Reports. https://doi.org/10.1038/s41598-024-84811-4
