Extensive fieldwork across a complex landscape
Our 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 we 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 us 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, we sought to answer a pressing environmental question: How far do pesticides travel in the Upper Rhine region?
Given the challenging logistics, we could often only sample a few sites per day. Depending on the location, we 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.
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. We 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. 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 our 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.
Mapping pesticide dispersal across the landscape
Using geostatistical modelling, we 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, our 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.
Implications and the need for action
Our 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. We 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.
In addition, large-scale pilot projects are needed to create pesticide-free cultural landscapes on a scale of 10 x 10 kilometers. This would be 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.