But frogs aren’t the only victims of rotary knives. This is evidenced by the numerous shear tests that Rainer Obermann and his team conducted in the meantime. “All potential grassland residents living between the ground surface and half a meter above the ground were affected,” says the researcher. The painting ranges from elk and baby rabbits to grass snakes and lizards to spiders and insects.
A team led by Johannes Stedel of the University of Hohenheim fears that mower death could be a previously underestimated factor contributing to the much-discussed insect death. In one study, scientists examined the effect of mowing and roadside coverings on insect fauna there. This is an interesting question, because such dams and green stripes can be very important habitats for six-legged friends. After all, there are about 6,800 square kilometers of it in Germany, which is almost 2% of the country’s total area. And unlike lawns, not all of these areas are used commercially. Accordingly, they are usually mowed once or twice a year and are largely exempt from fertilizers and pesticides.
According to Johannes Steidle and colleagues, roadsides can become refuges that prevent the local extinction of insect species. Meanwhile, animals can use such corridors to migrate to other habitats and thus ensure genetic exchange between populations. At least if your cover mowers aren’t getting in your way.
The team tested what these devices could do along roads in Baden-Württemberg. A conventional mulch head was used for embankments and roadsides, which works on the principle of rotation. In these experiments, researchers documented heavy losses. 29 percent of the insects and about half of the spiders and scadas were killed in the covered areas. Flies, mosquitoes and hymenopterans, including bees and wasps, lost almost half of their representatives. Even insect larvae killed 73 percent and butterflies 87 percent.
Alternatives are available
There are now also special “eco-mowers” for mowing roadsides, which are advertised as particularly insect-friendly. The researchers also tested such a model, which comes from the same company as the traditional capping head, for comparison purposes. This device cuts no deeper than ten centimeters above the ground and, thanks to the specially designed blades, has a smaller attack surface than a conventional rotary mower. In addition, the shape of the blades and the largely closed underside of the eco-mower are intended to prevent insects from getting sucked into the mower by dangerous suction. And, finally, the material is not covered with a lid, but rather sucked from above and transported away by a developed air duct.
In fact, this technique appears to save the lives of insects, as studies by Johannes Stedel and colleagues show. In spiders, cicadas, bedbugs, butterflies and insect larvae, there is no longer any evidence of any loss. In the case of the hymen there were at least 15 percent less losses and in the case of diopters the losses were 25 percent less. “In our view, investments in innovative technology therefore have great potential to effectively reduce insect degradation in grasslands,” Steidle says. This can be an important component in controlling insect mortality, especially on heavily maintained roadsides that are mowed only once or twice a year.