Context: 

Researchers from the University of Cambridge found that urban wildflowers may absorb toxic metals from polluted soils and pass them on to the pollinators like bees through their nectar.

Key highlights of the study

• Plants like white clover and bindweed absorb harmful heavy metals such as arsenic, cadmium, chromium, and lead from polluted soil. 
• Later, when Bees collect nectar from these flowers, they unintentionally consume these metals.
• Low levels of heavy metals in nectar can affect learning, memory, and foraging efficiency in Bees, ultimately contributing to their population decline and higher mortality

Observations of the study:

• Chicory (Cichorium intybus) recorded the highest total concentration of metals among all the sampled plants.
• White Clover (Trifolium repens) showed the highest levels of lead in nectar.
• Lead emerged as the most prevalent metal across all nectar samples, followed by chromium, cadmium, and arsenic.
• Only the common dandelion (Taraxacum officinale) did not show significant variation in metal uptake, indicating it may possess an inherent ability to limit metal transfer into its nectar.

Species-Specific Metal Absorption 

• Asclepias Syriaca (Common Milkweed): Absorbed the highest levels of arsenic.
• Wild Carrot: Recorded the highest concentrations of cadmium.
• Chicory: Accumulated the most chromium.
• White Clover: Contained the highest levels of lead in its nectar.

The study also cited growing evidence of sharp declines in wild pollinator populations, by more than 50 per cent in the past 50 years, due to changes in land use. 

Climate change and pesticide use were also identified as contributing factors, particularly by accelerating the loss of flower-rich habitats essential for pollinators.

Key Recommendations of the Study

• Soil Testing & Remediation: Test soil quality before sowing wildflowers. If contamination is detected, prioritize remediation efforts to ensure a safe growing environment.
• Managing Wildflower Growth in Contaminated Areas: In already polluted areas, control wildflower growth through regular mowing. This limits blooming time, reducing bees’ access to contaminated nectar.
• Informed Urban Planting Practices: Assess historical land use and soil quality before planting. Proactive planning and awareness can prevent unintentional harm to pollinators.