Image of strip-cropping fields located on the Droevendaal Experimental Farm in Wageningen, Netherlands. Image credit: Croijmans et al. (CC BY 4.0)
Insects are the largest and most diverse group of animals, comprising approximately 80% of all animal species. They inhabit nearly every place on Earth and play important and varied roles in ecosystems, from serving as a food source for other animals and as recyclers of organic matter and nutrients, to acting as crop pollinators and pest controllers.
Sadly, insect biodiversity is declining worldwide, with agriculture being a major contributor to this decline. For example, monoculture farming is a common form of farming where only one crop species is grown at a time, providing limited habitats and food resources for insects. By cultivating a diversity of crops in narrow, alternating strips, a technique known as strip cropping, farmers might make fields more suitable for insects, without reducing crop yield and productivity. However, so far, it was unknown if strip cropping can indeed increase insect biodiversity.
Croijmans et al. set out to investigate whether strip cropping can increase the biodiversity of ground beetles. Ground beetles play a key role in agricultural ecosystems, preying on common insect pests and weeds. They are sensitive to changes in farming practices and are often used as an indicator of agricultural sustainability. For this purpose, the researchers analysed four years of data from four organically managed experimental farms in the Netherlands, which included a diverse set of crops.
Croijmans et al. found that strip-cropped fields have more beetle species and more individual beetles than monocultures. As different ground beetle communities have natural preferences for specific crops, it is thought that the higher number of ground beetle species in strip-cropped fields is mostly due to the combination of two crop-related communities, rather than species unique to strip cropping. For example, if cabbage is strip-cropped with wheat, one would mostly find the ground beetle species corresponding to both cabbage and wheat, but few additional species. Interestingly, some ground beetle species preferred strip-cropped fields, while others preferred monocultures.
In conclusion, strip cropping can be a strategy to increase ground beetle biodiversity without losses to crop production. Therefore, farmers wanting to increase biodiversity might consider this approach instead of standard monocultures. Many biodiversity-increasing measures, such as flower strips or hedgerows, take up land that might otherwise be used for crop production. Strip cropping allows a more biodiverse field while keeping all land in production, making it a biodiversity measure that enables farmers to maintain the same level of crop production.
