Swedish flower-strip initiative boosts pollinators - with variable effects in crops

Flower strips are established as part of initiatives such as "Hela Sverige blommar" (Sweden Blossom), in which farmers sow flowering plants to support bees and other pollinators.

"Hela Sverige blommar" is a collaborative project demonstrating how small measures in agricultural landscapes can yield large ecological benefits. By setting aside a small portion of their fields for flowering zones, such as field margins and flower strips, farmers create habitats for pollinators and other beneficial insects. By July 2025, 4000 farmers across the country had applied for compensation covering a total area of 13 500 hectares, roughly equivalent to 25 000 football pitches.

In a new study, researchers investigated how annual flower strips affect several groups of arthropods, not only pollinators, but also natural enemies of pests and herbivorous insects.

– Our results clearly show that annual flowering field margins do what they are intended to do. They significantly increase the abundance of pollinators, says lead author Neus Rodríguez-Gasol.

At the same time, the researchers observed that flower strips also influenced other insect groups. Some natural enemies, such as hoverflies and predatory beetles, increased in number. However, several herbivorous insect species also became more abundant in the flower strips.

– It is important to remember that measures like these do not affect just a single group of organisms. We see both positive and potentially negative effects at the same time, says Neus Rodríguez-Gasol.

Limited effects observed in the crop despite spillover

A key question was whether the effects of flower strips spill over into adjacent crops, in this case, spring barley. The study shows that both beneficial organisms and herbivores do move into the crop to some extent from the flower strips.

– We observed that some insects spread about ten meters into the field. However, this did not translate into any clear changes in pest abundance in the crop itself, says Mattias Jonsson.

Despite higher numbers of natural enemies near the flower strips, the researchers did not observe any clear increase in above-ground biological control. However, there was a tendency toward increased predation on aphids by ground-dwelling predators near the strips.

– This suggests that certain ecosystem services may be strengthened locally, but the effects depend on which group of organisms you look at, says Maria Viketoft.

Important to adapt to local conditions

The results indicate that flower strips can contribute to multiple ecosystem services, but also that their effects vary and may sometimes be absent in the crop.

– There is no universal solution. To maximize benefits, flower strips need to be designed with local conditions and specific goals in mind, says Maria Viketoft.

The researchers believe the study provides important knowledge for future environmental measures in agriculture, where the aim is to combine high production with increased biodiversity.

– Flower strips have great potential, but we need to improve how we design them so they support multiple functions simultaneously and minimize unwanted effects, says Neus Rodríguez-Gasol.

Read more

Read the scientific paper Perennial flower strips increase pollinator and natural enemy abundance but have limited effects on pest control in adjacent crops in the journal Agriculture, Ecosystems & Environment.