The positive impact of hedgerows in providing ecosystem services on farmland has been widely documented – but `research from Belgium suggests that their effects may be more nuanced in regard to pest control.
The work explored the impact of numerous landscape features around 80 winter wheat crop fields over two years. In particular, focus was on the impact of hedgerows and grassy strips on populations of key crop pests – aphids and slugs – as well as three types of natural enemies of such pests: spiders, ground beetles and parasitoid wasps.
In results described as “quite unexpected,” hedgerows and wooded areas at field boundaries were linked with increases in pests and reduced numbers of natural enemies, while greater numbers of natural enemies and lower were seen in grassy strips.
Contentious findings?
The findings were highlighted as potentially controversial by the scientists involved, though they stressed that despite the study’s data suggesting an at-best mixed role for hedgerows and woods in reducing crop pests, they are necessary to promote broader biodiversity in agroecosystems.
As well as serving as dispersal corridors for species and overwintering habitat, they said, these habitats also provide other valuable services to farmers, such as windbreak effect, soil stabilisation and carbon storage.
Food for thought
Based on the findings, more care should be taken in making decisions on the structure of agricultural ecosystems, they suggested. A combination of woody and grassy habitats could provide a broader range of features than simply considering hedgerows and woods “unique cornerstones of agro-ecological landscape design strategies.”
“Of course, there is no ‘one-size-fits-all’ answer to the preservation of biodiversity and ecosystem services in agricultural landscapes,” the authors concluded.
“Finding the ‘ideal landscape’ will require consideration of the best agriculture-biodiversity and services-disservices trade-offs.”
You can read the full study in Science of the Total Environment.
