Prairie strips, such as these planted along the contour of a farmed hillside in Iowa, can boost biodiversity and protect ecosystem services. Credit: Lynn Betts
As human land use intensifies, agricultural landscapes are becoming more and more common. These landscapes are often reduced to only one or a few crops, leading to a massive decline in biodiversity. This decline has been particularly evident for insects, which are not only highly diverse but also provide valuable ecosystem services such as pollination.
One answer to combat this loss of biodiversity is in the form of natural habitat strips that act as corridors within or around agricultural landscapes. These strips can be made of grasses, wildflowers, or other types of native vegetation that support higher biodiversity than fields with only a single crop. Several recent studies show how grassland and wildflower strips act as corridors, and how agricultural landscapes can benefit from having even just a small portion of adjacent native vegetation.
Bees, hoverflies, carabid beetles and spiders represent a significant part of the insect diversity found in and around grasslands. These predators and pollinators were sampled across newly established grassland strips in cereal fields in Austria to test whether the strips act as temporary dispersal corridors.
After 3 years and over 30,000 recorded insects, newly established grassland strips supported larger sized and actively foraging or hunting species in the agricultural landscape, with pollinators appearing to adopt newly established grasslands more rapidly than predators. However, that 3-year period is likely too short to enhance functional diversity and related ecosystem services, meaning that the creation of new grasslands needs to be accompanied by the protection of old grasslands to be most effective.
Native vegetation strips can benefit not only movement, but reproduction as well. Seven species of solitary bees in Switzerland were used to compare reproductive success between wildflower strips, semi-natural habitats (forest edges), and isolated sites lacking both.
Large cabbage white (Pieris brassicae). Credit: Zeynel Cebeci
Across almost 600 nests, bees in wildflower strips had higher reproductive success, in part because pollen from wildflowers allowed for shorter foraging trips and therefore better food provisioning for offspring. Dense networks of floral resources such as wildflower strips among agricultural landscapes could increase connectivity of foraging and nesting sites and effectively promote solitary wild bee populations.
Bees aren’t the only insect that show clear responses to wildflower strips. Butterfly abundance, species richness, and flight behavior were tracked along linear field margin strips on a farm in the UK, half of which had been sown with wildflowers two years earlier.
Recorded flight paths showed that field margin strips are very effective at funneling butterfly movements in linear directions, regardless of whether wildflowers had been sown. However, while wildflower-sown strips did not affect movement patterns within them in terms of speed or efficiency, it did enhance butterfly abundance by 78%. Providing natural vegetation strips around agricultural fields aids in connectivity for butterflies, and adding in wildflowers provides the additional benefit of foraging resources without interfering with movement.
Resources
Maas, B., Brandl, M., Hussain, R.I., Frank, T., Zulka, K.P., Rabl, D., Walcher, R. and Moser, D. 2021. Functional traits driving pollinator and predator responses to newly established grassland strips in agricultural landscapes. Journal of Applied Ecology. DOI:10.1111/1365-2664.13892.
Threadgill, K.R., Hodgson, J.A., Jones, N., McClean, C.J. and Hill, J.K. 2021. Quantifying trade‐offs between butterfly abundance and movement in the management of agricultural set‐aside strips. Insect Conservation and Diversity. DOI: 10.1111/icad.12511.
Ganser, D., Albrecht, M. and Knop, E. 2021. Wildflower strips enhance wild bee reproductive success. Journal of Applied Ecology 58(3): 486-495.
Prairie strips provide wildlife habitat within the agricultural matrix (September 2019)
