Landau, 12.03.2025 – A new study by the RPTU Kaiserslautern-Landau, published in Communications Earth & Environment, shows extensive pesticide contamination in the landscape of the Upper Rhine Region. Pesticides disperse across the entire landscape, contaminating soil, vegetation, and water far beyond agricultural zones. The findings shed new light on the potential environmental impacts of conventional agriculture. According to the researchers, pesticide use must be reduced urgently in order to protect non-target areas around fields, orchards and vineyards.

Extensive fieldwork across a complex landscape

The goal was to visualise the spread of current-use pesticides beyond farmland and into areas where they were never intended to be. This required not only trace analytical techniques with high sample throughput but also a significant amount of fieldwork—often in challenging terrain, from intensively farmed lowlands to the remote mountain ranges of the Black Forest and the Palatinate Forest.

The idea for this study was inspired by previous research conducted in the Vinschgau Valley in South Tyrol, a region known for its intensive apple orchards. That study revealed pesticide contamination far beyond the treated areas, and the researchers thought: The Vinschgau is essentially a miniature version of our Upper Rhine Valley. If contamination occurs there, how extensive might it be in a much larger agricultural basin with a wide range of different crops?

Field research is rarely as simple as marking locations on a map and taking samples. The journey took the team across dense agricultural landscapes, crossing puddles and small streams, and up steep inclines. Reaching sampling sites was often an adventure, navigating dense terrain, and adapting to unpredictable conditions. With every step, they sought to answer a pressing environmental question: How far do pesticides travel in the Upper Rhine region?

Given the challenging logistics, the researchers could often only sample a few sites per day. Depending on the location, they travelled by car, by mountain bike, or even on foot to reach the most inaccessible spots. “It was astonishing to see how some nature conservation areas were completely surrounded by farmland, while others lay deep in the Black Forest, far away from any agricultural activities. In some areas of the agricultural basin of the valley, the search for non-target sampling locations proved particularly difficult. Sometimes, fields were so densely packed that there simply were no uncultivated spaces available “, explains Ken Mauser, lead author of the study.

Contamination from the lowlands to the highlands

Once analyzed, the samples revealed staggering results: pesticides were detected in 97% of all soil and vegetation samples, often as complex mixtures. The study identified residues from 63 different pesticides, with an average of five active ingredients in topsoil and six in vegetation. In some locations, up to 26 pesticides were found in a single soil sample and 21 in vegetation.

“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. 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 detected pesticides was fluopyram, a fungicide classified as a PFAS, or “forever chemical,” known for its persistence in the environment. The widespread presence of such substances raises concerns about their potential to contaminate groundwater and drinking water resources in the Upper Rhine Valley.

Pesticide ‘cocktail effect’ and environmental risks

A major finding of the study was the frequent occurrence of pesticide mixtures, or “cocktails,” in environmental samples. In total, 140 different combinations of at least two active ingredients were detected. This is particularly concerning because pesticides are assessed for regulatory approval as individual substances, not as mixtures. However, real-world exposure involves complex combinations, which can lead to unexpected interactions and amplified toxicity.

“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.”

Mapping pesticide dispersal across the landscape

Using geostatistical modelling, the research team created predictive contamination maps for the entire study area. The results highlight contamination hotspots, including nature conservation areas that should serve as refuges for biodiversity.

According to the model, intensively cultivated wine-growing regions such as the Southern Palatinate and the Kaiserstuhl are contaminated with 10 to 20 different pesticides in topsoil and vegetation. Areas outside farmland, including flower strips, hedges, adjacent grasslands, as well as designated nature reserves and national parks, are considered refuges for protected plant and animal species. However, the study reveals that even these supposedly safe areas—whether within the agricultural landscape or in remote locations such as the Black Forest National Park and the Palatinate Forest-North Vosges UNESCO Biosphere Reserve—are affected by pesticide contamination.

In the Black Forest National Park alone, residues of four different pesticides were detected, while three substances were found on the Feldberg (1,494 meters a.s.l.). Further modelled was the “Kleine Kalmit,” a nature conservation area near Landau in the Palatinate, predicted up to 15 different pesticides in soil and vegetation—a result confirmed by previous measurements.

Pesticide contamination not only threatens protected species but also undermines efforts to conserve biodiversity. “Protected areas near conventional fields show elevated pesticide contamination. Establishing sustainable, pesticide-free managed fields could help reduce pesticide exposure of those reserves,” explains Ken Mauser.

Implications and the need for action

The study provides clear evidence that pesticide contamination is not just an agricultural issue—it affects entire landscapes. Contaminated nature reserves threaten biodiversity conservation efforts, while pesticide exposure poses risks to human health. 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:

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