Extensive use of fertilisers in agriculture grasslands significantly reduces the population of pollinators and the number of flowers, a two-year study at the world's longest-running ecological experiment, Park Grass, Rothamsted, has found. The research results, published in the journal npj Biodiversity, show that even moderate application of nitrogen fertilisers leads to a dramatic decrease in flower numbers, reducing them by fivefold, while also halving the population of pollinating insects like bees.
Almost a quarter of the Earth's land area is agricultural grassland, contributing to the livelihoods of over 800 million people. While fertilisation methods have boosted global food production, it has come at a substantial environmental cost -- leading to an increase in air, and water pollution as well as loss of biodiversity.
Pollinators are vital to agricultural productivity and maintaining natural ecosystems. Their absence can have devastating consequences in balancing the delicate ecosystem. Dr Nicholas Balfour, lead researcher from Sussex University, emphasised the direct link between fertiliser use and the decline in pollinators, noting the cascading effects up the food chain
"As you increase fertilisers, pollinator numbers decrease - that's the direct link that to our knowledge has never been shown before. It's having a drastic effect on flowers and insects. The knock-on effect goes right up the food chain," Dr Balfour was quoted as saying by The Guardian.
When allowed to roam in chemical-free plots, the population of bees shot up over nine times. Meanwhile, in plots treated with fertiliser mix excluding nitrogen, a relatively high number of pollinators and flowers were found as well-- suggesting that nitrogen-fixing was causing the most damage.
As per the study, the use of fertiliser creates conditions that allow fast-growing grasses to dominate an area which practically drowns other grasses and flowers. Scientists are of the view that having a diversity of flowers leads to a greater diversity of pollinators
"While reduced yields aren't typically thought of as a good thing, reducing grassland production intensity has the potential to realise many of the benefits of multifunctional landscape," said Dr Balfour.
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What is the Park Grass Experiment?
Set up in 1856, the Park Grass Experiment at Rothamsted, southeast England, is the world's longest-running ecological experiment, still going strong after 169 years. Though the original aim of the project was to investigate ways to improve pasture productivity via organic and inorganic soil fertilisation, its objective has evolved since then.
Park Grass has proved of great value in addressing a wide range of ecological, environmental and evolutionary questions, and continues to be a valuable resource for gaining new insights into agroecological systems
