IN YEARS gone by, it was par for the course for farmers to leave swathes of land fallow to improve productivity.
But as the effectiveness of fertilizer rose - and more recently, EU set-aside payments ended - the practice dramatically reduced.
Now a researcher from the University of Leeds says bringing back the practice could be key to halting the decline in the numbers of bees and other pollinating insects - by encouraging the growth of wild flowers.
Professor Bill Kunin, Professor of Ecology in the University of Leeds’ Faculty of Biological Sciences, worked with the University of Bristol on the first ever Britain-wide assessment of the value of wild flowers as food for pollinators. By examining vegetation surveys dating back to the 1930s, and carrying out their own research, they were able to show that decreasing resources mirror the decline of pollinating insects, providing new evidence to support the link between plant and pollinator decline.
The research shows substantial losses to nectar resources, the sugar-rich food source made by wild flowers, in England and Wales between the 1930s and 1970s – a period closely linked with agricultural intensification.
By 1978, the researchers discovered that nectar resources had stabilised and actually increased from 2000.
Prof Kunin said they were not able to pinpoint exactly why nectar resources increased - but it was likely to be a combination of factors, including the acid rain coming under control, and the increasing popularity of European set-aside payments, which encouraged farmers to leave areas fallow.
This however, ended in 2008 - and as the research only examined data a recent as 2007, it’s impossible to know the impact it will he had on pollinators.
Clover is one of four plant species that account for more than half of all pollinators in Britain - and is often grown on land left fallow. Encouraging farmers to plant clover or other wild flowers on land left fallow could have an impact, particularly on bumblebees, Prof Kunin said,
He added: “Farmers on Agri-environment schemes can plant wild flowers to help improve the value of their land for pollinators, but the areas involved have been small and thus the contribution to floral resources at the national scale is still low. On the other hand, there are vast areas of improved grasslands, and small changes in management to increase wild flowers could make a huge contribution nationally.”
The study also looked at the type of habitats most beneficial for pollinators, highlighting arable land as the poorest source of nectar: both in terms of amount and the diversity of sources. Improved grasslands could however contribute the most to national nectar supply if management favoured greater flowering of plants such as white clover.
Prof Kunin added: “Wild bees and other insect pollinators are vital to the success of many important food crops and wild plants. It is therefore really important that we understand the relationships between floral resources and pollinating insect populations.
“Despite the stabilisation seen recently, our research shows significant long-term declines in the diversity of nectar sources mirrored in a fall in the diversity of pollinator species. We are at a point where only four plant species account for more than half the nectar in Britain.