Traffic greenery supports pollinators, but pollution can disrupt their navigation

Green spaces in urban traffic environments provide important habitats for plants and pollinators, but heavy pollution can make it harder for insects to find flowers, Yle reports.

Researchers from the University of Turku’s Department of Biology surveyed vegetation in Helsinki, Turku and Tampere during the summer of 2022. They examined green areas in traffic environments, including traffic islands, car parks and roadside verges.

Plants can help retain and filter rainwater, reducing the risk of flooding. They also capture fine particles and dust from traffic, provide habitats for species beyond pollinators and add visual appeal, said Satu Ramula, a university lecturer at the Department of Biology.

Dandelions, autumn hawkbits and red clover are among the flowers suited to traffic environments. The researchers found that yellow and large-flowered species were more common in areas surrounded by traffic.

Ramula said excessive mowing should be avoided and carried out only when vegetation obstructs traffic. Continuous mowing disrupts species, while insect larvae and eggs attached to plants during the summer can be removed along with the vegetation.

Traffic can also kill pollinators, although the insects have adapted to urban conditions. Ramula said one estimate suggested that busy traffic may kill about one in 10 flying pollinators, and that this harm should be weighed against the benefits of green traffic environments.

Pollinators are exposed to heavy metals released by traffic. Species differ in how well they tolerate the metals and how much accumulates in their bodies, which may increase insect mortality.

Heavy metals may also cause behavioural problems, making it difficult for pollinators to find food plants and navigate towards them, Ramula said.

The researchers found that the diversity of plant characteristics declined as the amount of impermeable, built surfaces increased.