Wildflowers cultivated on urban lands previously used for industrial activities may pose risks to bee populations due to accumulated metal contaminants, according to a new study. Researchers found these contaminants, ingested by pollinators through nectar, detrimentally affect bees' health by impairing their learning and memory, diminishing population size, and increasing mortality rates.
The study, published in the journal Ecology and Evolution, notes that common urban plants such as white clover and bindweed accumulate metals like arsenic, cadmium, chromium, and lead from contaminated soils. These metals, originating from sources like cement dust and mining, pose a persistent problem in older cities worldwide.
Researchers suggest municipal soils undergo metal testing prior to planting wildflowers, with potential remediation of polluted sites. The study emphasizes the selection of suitable wildflower species to minimize metal exposure, a critical concern for the success of urban pollinator conservation programs.
Lead author Dr. Sarah Scott from the University of Cambridge commented on the results: “It’s really important to have wildflowers as a food source for the bees, and our results should not discourage people from planting wildflowers in towns and cities. We hope this study will raise awareness that soil health is also important for bee health."
Conducted in Cleveland, Ohio, a city rich in vacant lots due to its industrial past, the research examined self-seeded flowering plants for metal concentration. Lead was frequently observed at the highest levels in the nectar of these plants. Chicory was identified as the plant accumulating the largest total metallic concentration, followed by white clover, wild carrot, and bindweed, all essential urban forage plants for pollinators.
The research highlights a decline in wild pollinator populations by over 50% over the past five decades, attributed primarily to habitat loss, climate change, and pesticide use. Pollinators contribute significantly to food production, assisting in the pollination of plants such as apples and tomatoes, and their natural services contribute billions of dollars to global crop productivity.
Scott further noted: “Climate change feels so overwhelming, but simply planting flowers in certain areas can help towards conserving pollinators, which is a realistic way for people to make a positive impact on the environment.”
The study received its primary funding from the USDA National Institute of Food and Agriculture.
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