Species protection: New mowing technology protects insects

Meadow

Mown meadow. © Astrid860/ iStock

When meadows and other grassland are mowed, this often has negative consequences for the insects that live there. A new mowing head, which works more gently on insects, could now remedy the situation, as initial tests have shown. In some species, such as butterflies and bugs, mowing has even completely prevented insect mortality.

Industrialized agriculture is considered to be one of the main factors responsible for insect mortality in recent decades. Above all, the large monocultures lead to a loss of habitats and structural diversity. However, according to experts, modern mowing machines are also contributing to a decrease in biodiversity. While these are highly efficient for maintaining green spaces, their use kills a significant proportion of small meadow dwellers – a critical factor in the dramatic decline in insects in Europe and globally.

The consequences of the mowing

Mowing is dangerous for the insects that live on meadows and green spaces for two reasons: Firstly, many insects sitting in the grass are killed by the mowing process itself. But mowing is also problematic because it deprives the insects of important resources. “It reduces the quality of the habitats for insects because, for example, flowering plants do not develop. On municipal green spaces and on roadsides, the clippings left on the areas also lead to an oversupply of nutrients,” explains Johannes Steidle from the University of Hohenheim.

He and his colleagues have now investigated the effectiveness of a number of technological innovations designed to mitigate the immediate effects of mowing on the insects. An embankment mower head, which is specially designed to protect insects, serves as an example for the investigation. The new mowing head has a reduced contact area with the grass compared to conventional devices and an increased cutting height of at least ten centimeters above the ground. In addition, the new generation of mowing heads should prevent insects from being sucked up, since the underside is largely closed and no vertical air flow is generated from bottom to top.

Insect deaths at the roadside

The researchers investigated the effect of the classic and new mowing technology on insects by mowing green verges along roads. There, the consequences caused by mowing are particularly critical because these green strips often serve as corridors for insect populations to network. “Consistent with previous studies, we found that mowing with a conventional mowing head resulted in significant losses in arthropods,” Steidle and his colleagues report. After mowing, the number of bugs was reduced by 30 percent and that of spiders, leafhoppers, hymenoptera and dipterous insects, such as mosquitoes and flies, by as much as 50 percent each. The most significant losses, however, were butterflies, whose populations fell by 87 percent after mowing.

According to Steidle and his team, these results underline the negative impact of conventional mowing heads: “These data show that mowing roadsides with conventional mowing technology has a very adverse effect on grassland arthropod fauna”. However, after mowing with the “insect-friendly” mowing machine, there were significant improvements in insect populations: spiders, leafhoppers, bugs, butterflies and several insect larvae did not seem to bother the mowing process at all, because the researchers did not record any losses among them. For winged insects such as mosquitoes, horseflies, flies, bees and wasps, the decline was reduced by 15 to 25 percent.

New technology has potential

The research team therefore draws a positive balance: “This technology has great potential to reduce insect decline in grassland on roadsides and thus turn these areas into a habitat for insects,” they explain. This is particularly important with regard to the biodiversity of our ecosystems. Because when insect populations decline, this loss also affects fungi, plants, animals and ultimately also us humans. Investments in innovative techniques therefore have a high potential to reduce insect decline in grassland and thus maintain the function of ecosystems, according to Steidle.

Source: University of Hohenheim; Article: Journal of Applied Entomology, doi: 10.1111/jen.12976

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