Urban development has a significant impact on the habitats of many animal species. Pollination is a vital ecosystem function for terrestrial ecosystems and food security. However, a quantitative meta-analysis of the overall impact of urbanization on pollinator diversity and pollination service is lacking.
A team of researchers from the Wuhan Botanical Garden (WBG) of the Chinese Academy of Sciences (CAS) and the Martin Luther University Halle-Wittenberg conducted a comprehensive meta-analysis of 133 studies to investigate how urban growth affects pollinators and their pollination performance. The analysis considers all continents of the world except Antarctica.
The results show that butterflies are particularly vulnerable to changes in their environment as a result of urbanization. "They depend on very specific plants for their nutrition and larval development. Since these are found less and less in cities, the populations of many butterfly species are also declining," said Dr. LIANG Huan from WBG.
Pollinators that are active in early spring and feed on the nectar and pollen of early-flowering plants are also particularly affected. Wild bees that nest in the ground often lack suitable breeding sites in cities and their populations are declining. Less affected, on the other hand, are wild bees that nest above ground, in cavities or in insect hotels.
Surprisingly, despite the negative effects of urbanization on pollinator diversity, pollination performance, as measured by seed set, is improved in non-tropical cities. According to the researchers, this is mainly due to the abundant generalists and managed pollinators therein.
"Honeybees are very productive and are kept by hobby beekeepers in many places," said LIANG. While this is good for urban plants, it can negatively impact other pollinators because honeybees often displace other native pollinators and can transmit diseases to wild pollinators.
The results demonstrate the magnitudes of multiple moderators on urban pollinators and pollination services, highlighting the importance of nature conservation efforts in urban areas.
The study was published in Ecology Letters entitled "The effects of urbanization on pollinators and pollination: A meta-analysis" and was funded by CAS and the National Natural Science Foundation of China.
