Insect walls: New tool models where planted walls on fields prevent erosion and retain water

A narrow earth bank on a slope can protect against erosion – if it is in the right place. These so-called insect walls are created on agricultural land, are around half a meter high and are usually overgrown with native wild herbs and grasses. They not only slow down water runoff and reduce erosion, but also provide protection for beneficial insects such as ground beetles. For them to be effective, they need to be placed in the right places. Researchers at the Leibniz Center for Agricultural Landscape Research (ZALF) have developed a digital tool that can be used to determine suitable locations for insect walls. The results based on modeling are now to be put into practice for the first time: Insect walls will be created on test areas in Bavaria from 2026 and their effect investigated.

Insect walls are built across the slope to retain water, prevent erosion and create a habitat for insects. The research results show: Their effect depends heavily on their placement. Incorrectly placed embankments can even increase erosion. The new digital tool was developed as part of the Digital Knowledge and Information System for Agriculture (DAKIS) project. It not only analyzes the terrain, but also takes lane planning and the use of machinery into account.

A key aspect is the consideration of lane planning in conjunction with a detailed terrain model. Until now, agricultural software has primarily optimized lanes based on the shape and boundaries of the field in order to save time and fuel. The slope gradient is usually not taken into account, although tracks along a slope can even increase erosion. The new model integrates high-resolution digital terrain data with a resolution of one meter and suggests tracks for cultivation across the slope – but only where this is compatible with the practical requirements of agriculture.  

In addition, the method enables the targeted integration of insect barriers as a protective measure. Existing models generally only place agri-environmental measures such as flowering or erosion control strips at the edges of fields. Insect barriers, on the other hand, should be placed as centrally as possible in the field, which makes it difficult for agricultural machinery to bypass them. The model therefore calculates how the walls can be optimally integrated into the lane planning so that they can be bypassed. A height profile analysis also determines the points at which the embankments can usefully retain water in the area.  

The researchers hope that this approach will have additional effects on the landscape water balance. “During heavy rainfall, water should remain on the land and later supply the plants. Fewer nutrients and pesticides end up in the water and settlements could be better protected against flooding,” explains Marvin Melzer from ZALF, lead author of the study and researcher in the DAKIS project.  

The study involved modeling how water runoff in the landscape affects different wall heights (40 cm, 50 cm). The simulation shows: Well-planned insect walls divert water in a controlled manner and reliably protect downhill farmland from erosion. “The new method could be integrated into the lane planning software of well-known agricultural machinery manufacturers. Farmers will have a tool that combines lane planning, erosion control and biodiversity – without much additional effort in cultivation,” explains Marvin Melzer.

Until now, the findings of the study have only been modeled, but this is now set to change. In the second funding phase of the DAKIS project (DAKIS2), it is planned to test the digital method in practice for the first time. In Bavaria, together with the Bavarian State Institute for Agriculture (LfL) and in collaboration with farmers, targeted insect walls will be created whose location and design will be based on the model calculations. The researchers will not only investigate whether the digital planning achieves the hoped-for effects on water retention and erosion control, but also how the measures can be integrated into everyday farming life in the long term.

The digital tool could help to link agricultural subsidies more specifically to ecologically effective measures. Currently, many agri-environmental programs reward measures mainly according to their area size, without taking into account their actual ecological effectiveness. Although insect walls can already be funded as part of agri-environmental and climate measures (AUKM) in certain regions, such as Bavaria, the funding opportunities in Germany vary depending on the federal state. While some programs support erosion control measures or the promotion of beneficial insects, there is currently no specific premium for insect walls. The new model shows where they can have the greatest effect on erosion control, water retention and biodiversity. This means that in future, more funding could flow into measurably effective measures and farmers could receive targeted support in implementing sustainable protection measures.

• Leibniz Center for Agricultural Landscape Research (ZALF)
• Bavarian State Institute for Agriculture 

This work was produced as part of the project “Digital Agricultural Knowledge and Information System” (DAKIS, funding code: FKZ 031B0729A), funded by the Federal Ministry of Education and Research (BMBF). Olivia Spykman’s contribution was funded by the Bavarian State Ministry of Food, Agriculture, Forestry and Tourism (funding reference A/21/17).

• Link to the original publication: https://www.sciencedirect.com/science/article/pii/S0006320725000369?via%3Dihub
• The tool was published (in addition to the publication) as a software package: https://doi.org/10.5281/zenodo.14272617
• The EROSPOT web app shows results for selected regions (water catchment areas) in 3D: www.erospot.de