The primary threat to biodiversity is urbanization. However, scientists know little about how urbanization affects biodiversity and ecosystem services in the Global South’s tropical regions. An international research team led by the German universities of Göttingen and Hohenheim, in collaboration with the Indian University of Agricultural Sciences, investigated the effects of urbanization on bee communities in smallholder farms in and around Bangalore, a South Indian city of more than 13 million people.
They discovered that social bees, such as wild honey bees, suffered more than large solitary bees or those that nest in cavities, contrary to temperate region results. Native flowering plants near farmland and crop diversification can help keep bee populations healthy. The research was published in the journal Ecological Applications.
The researchers recorded over 26,000 individual bees belonging to 40 species during an extensive field survey of bees on vegetable farms ranging from rural to urban settings. The scientists were able to determine how the proportion of sealed surfaces and buildings in metropolitan areas affected bee communities by combining the data with satellite remote sensing. They also analysed how bee species responded to the environments, comparing bees that use different nesting sites and differ in sociality and mobility.
Our results suggest that urban agriculture can promote bee communities if managed in a sustainable manner and could combine to support wild bee conservation and food production in and around cities.
Professor Catrin Westphal
“We demonstrated that the way bees responded to urbanization were specific to certain traits. For example, bees nesting in cavities actually benefited from urbanization as they can nest in small cracks and cavities on buildings,” says first author Gabriel Marcacci, Ph.D. student in the Functional Agrobiodiversity group at the University of Göttingen. He continues, “Moreover, we found that ground-nesting bees, which are usually considered the losers in urbanization, find ample nesting opportunities in tropical megacities because enough bare ground is still available, mostly in the less developed neighbourhoods.”
In collaboration with the University of Agricultural Sciences of Bangalore in India, an international research team led by the German universities of Göttingen and Hohenheim looked into the effects of urbanization on bee communities in smallholder farms in and around Bangalore, a city in South India with a population of more than 13 million.
They discovered that social bees, such as wild honey bees, suffered more than large solitary bees or those that nest in holes, contrary to findings from temperate locations. Native flowers near farms and agricultural diversity can help bee populations survive. The findings were published in the journal Ecological Applications.
The researchers tallied more than 26,000 individual bees from 40 species during a thorough field study of bees on vegetable fields spanning rural and urban habitats. The scientists were able to determine how the percentage of sealed surfaces and buildings in urban areas influenced bee colonies by combining the data with remote sensing from satellites. They also compared bees that use various nesting locations and have various social structures and levels of mobility to examine how the various bee species reacted to the settings.
“Our results differ in part from what is often found in cities in temperate regions,” explains Professor Ingo Grass of the University of Hohenheim’s Department of Ecology of Tropical Agricultural Systems, “which shows that we cannot generalize from field studies conducted in Germany or other countries of the Global North.” Another contrasting result of urbanization is a significant decline in social bees. “This finding is especially concerning because social bees, such as wild honeybees and stingless bees, form large colonies in the tropics and are critical for crop pollination,” explains Professor Teja Tscharntke.
The study also discovered that farm management practices such as crop diversification and the presence of wild native plants growing within and around vegetable fields have a positive impact on bee communities. “Our results suggest that urban agriculture can promote bee communities if managed in a sustainable manner and could combine to support wild bee conservation and food production in and around cities,” says Professor Catrin Westphal, head of Göttingen University’s Functional Agrobiodiversity group.
