Home gardens in cities are the largest source of food for pollinating insects like bees and wasps, according to researchers.
The study, conducted by the University of Bristol and published in the Journal of Ecology, found that residential gardens make up, on average, 85% of the nectar produced in urban areas.
The researchers found that an average of three gardens per day are created around a teaspoon of the unique sugar-rich liquid in flowers that pollinators drink for energy.
This equates to more than a ton of food for an adult human and is enough to fuel thousands of flying bees.
The more bees and other pollinators that can fly, the more diversity of flora and fauna is preserved.
Nicholas Tew, an ecologist at the University of Bristol, said, “Although the amount and variety of nectar was measured in the countryside, it was not in urban areas and we decided to investigate.
“We expected private gardens in cities to be an abundant source of nectar, but didn’t expect the levels of production to be so overwhelming.
“Our results underscore the key role they play in supporting pollinators and promoting biodiversity in urban areas across the country.”
The research was carried out in collaboration with the Universities of Edinburgh and Reading and the Royal Horticultural Society.
It examined nectar production in Bristol, Edinburgh, Leeds and Reading.
Nectar production was measured in nearly 200 plant species by extracting nectar from more than 3,000 individual flowers.
Mr. Tew, who is studying for a PhD in ecology, said, “We have found that urban nectar supplies are more diverse, in other words – (it) comes from more plant species than farmland and nature reserves, and that urban nectar supply is becoming critical underpinned by private gardens. “
“Gardens are so important because they produce the largest nectar per unit area and cover the largest area of land in the cities we studied.”
A fine glass tube was used for extraction and the sugar concentration of the nectar was quantified with a refractometer – a device that measures how much light is refracted as it passes through a solution.
A total of 29% of land in urban areas is made up of indigenous gardens – six times the area of parks and 40 times the area of allotment gardens.
Mr Tew said it was vital for new housing developments to include gardens and urged gardeners to ensure that their spaces are “as good as possible” for pollinators.
He suggested planting nectar-rich flowers to make sure there was always something in bloom from early spring to late fall, and mowing the lawn less often to allow dandelions, clover, daisies, and other plants to grow.
Gardeners should also avoid spraying pesticides, as these can damage pollinators, and avoid covering their gardens with paving stones, patios or artificial grass, he said.
Dr. Stephanie Bird, Insect Scientist at the Royal Horticultural Society, said, “This study highlights the importance of gardens in supporting our pollinating insects and how gardeners can make a positive impact through their planting decisions. Gardens shouldn’t be viewed in isolation – instead, they are a network of resources that provide valuable habitats and supplies when cared for with pollinators in mind. “
The paper Quantifying Nectar Production by Flowering Plants in Urban and Rural Landscapes was published in the Journal of Ecology.