Editor’s Choice 59:5: Rolling composite wildflower blocks as an alternative to wildflower strips to improve farmland biodiversity

Associate Editor, Erik Öckinger, introduces this month’s Editor’s Choice paper by Jana Eccard, which suggests that rotational wildflower blocks, where successional stages exist in parallel, could represent a novel improvement to the commonly used wildflower strips.

Strips with sown wildflowers along the margins of crop fields have become a common measure to counteract the ongoing loss of farmland biodiversity in many European countries. These wildflower strips provide resources for many insect species, and can increase ecosystem services such as pollination and pest control.

However, these strips are typically only temporary over a few years, and so are their positive effects. Also, their effect tend to depend on their age, as different species are associated with different successional stages of the strips. The fact that they are narrow and thereby strongly influenced by farming activities in the adjacent field can also reduce their positive effects.

Jana Eccard from the University of Potsdam, Germany, suggests a novel solution to overcome these shortcomings – Composite Wildflower Blocks. These would be blocks consisting of 4 strips next to each other. One strip is sown each year in order to achieve a variation in successional stages within the block. After 5 years, the first strip is re-sown so there will always be strips that are 1-4 years old within the block.

EC fig 2 — Life cycle of wildflower strips, light to dark: 1- to 3-year-old strip element. (a) Conventional short-lived wildflower (WF) strip sown in the first and removed after 3 years. Arthropod communities fluctuate with successional stage and finally disappear together with refuge, constructing an ‘ecological trap’ (Table 1). (b) Persistent, rotational, composite WF block, removal and re-sowing of WF strip elements, three successional stages are simultaneously available to wildlife. (c) Rolling, composite wildflower block and aged WF strips are removed at one end and new WF strips are sown at the other. (b) and (c) increase habitat heterogeneity and species richness and provide persistent refuges to wildlife. Compact shape reduces edge effects and pesticide spillover from the agricultural field. By reclaiming the area of the rolling strip for crops in (c) (dashed line), soil improvement through plants and animals may benefit agriculture

By including this variation of age classes within the block, and thereby allowing species associated with different successional stages to co-exist, Eccard estimates that a Composite Wildflower Block could contain 29-39% more species than a traditional wildflower strip of the same area. The benefit could potentially be even larger by reducing negative edge effects and facilitating colonization among strips within the block. The benefit of Wildflower Blocks would increase with its area, but in principle the area could be the same as for a traditional wildflower strip.

Composite Wildflower Blocks could either be permanent, with an internal rotation of strips of different ages, or consist of “rolling” blocks that gradually change position on the field over the years. This could have the benefit of importing soil structure and favouring soil fauna on the land that is returned to agriculture.

Composite Wildflower Blocks could be a promising way of increasing farmland biodiversity, but this remains to be tested empirically. Perhaps the paper by Eccard can inspire empirical studies that assess the benefits of wildflower block in different agricultural settings?

Read the full Policy Direction Can rolling composite wildflower blocks increase biodiversity in agricultural landscapes better than wildflowers strips? in Journal of Applied Ecology