Bees, butterflies, hoverflies and other pollinating insects are fundamental to the health of our planet, but their survival is increasingly threatened. A new study, the longest and most complete ever carried out on the subject, raises a disturbing alarm: excessive use of fertilizers is decimating pollinator populations in lawnswith potentially devastating consequences for the entire ecosystem.
The research, conducted byUniversity of Sussex and from Rothamsted Researchanalyzed the impact of fertilizers on strips of prairie called Park Grassstudied since 1856. The results, published in the journal Npj Biodiversityshow a direct correlation between the increase in fertilizer use and the decrease in pollinators.
“As fertilizers are increased, the number of pollinators decreases: this is the direct link which, to our knowledge, has never been demonstrated before,” Dr Nicholas Balfour from Sussex University, lead author of the study. “It’s having a drastic effect on flowers and insects. The ripple effect extends up the food chain“.
The study found that the increase in the quantity of nitrogen, potassium and phosphorus distributed on agricultural pastures it reduced the number of flowers fivefold and halved the number of pollinating insects. Bees were hardest hit: in chemical-free areas nine times more were present than to those with the highest levels of fertilizer.
But how can this phenomenon be explained? Fertilizers, especially nitrogen fertilizers, create conditions that favor the growth of fast-growing grasses, stifling wildflower diversity. This loss of biodiversity has a direct impact on pollinators, who often have specific needs in terms of the flowers they like to visit.
“What is interesting and new here is the timing,” the doctor explained Philip Donkersleysenior researcher in ecology and evolution at Lancaster Universitynot involved in the study. “Normally, our studies cover the last four or five years. That’s about 150 years of applying chemical and organic fertilizersand therefore much more representative of what happened on British farms.”
The study’s findings are even more worrying when you consider that almost all UK pastures are ‘improved’, meaning fertilized to some extent. Only 1-2% of UK grassland is high-quality, species-rich habitat. At the national level, the UK has lost 97% of its wildflower meadows since the 1930s and studies have shown widespread declines in the numbers of pollinating insects.
Farmers are therefore faced with a dilemma: to get more flowering plant species and pollinators, the land must be less fertile, which reduces yields. “Our most important and challenging finding is the existence of a trade-off between flower and pollinator diversity and pasture yield,” the researchers say in the study.
However, Balfour highlighted that “reducing the production intensity of rangeland has the potential to realize many of the benefits of multifunctional landscaping.” These include the benefits for pollinators, improved soil health, improved air quality and greater resilience to extreme weather events.
