What is the role of vegetation in reducing non-point pollution in urban areas?

• A. Vegetation increases impervious surfaces, leading to more runoff
• B. Vegetation slows runoff, promotes infiltration, traps pollutants, and can uptake nutrients and metals
• C. Vegetation has no effect on pollution
• D. Vegetation reduces evapotranspiration

Answer: (B)

Vegetation acts as a natural buffer that slows, filters, and stores stormwater in urban areas. Plants intercept rainfall and reduce the speed of surface runoff, giving water more time to infiltrate into the soil and recharge groundwater. The canopy, litter, and soil layers trap particulate pollutants and contaminants like oils, metals, and nutrients brought in by urban activities, preventing much of them from washing straight into rivers and streams. Roots and the surrounding soil biology take up nutrients, such as nitrogen and phosphorus, and some metals, reducing their concentration and transport. This combination also helps stabilize soils, lowering erosion and sediment delivery to waterways.

This is why vegetated features in cities—like bioswales, rain gardens, street trees, and green roofs—are effective at reducing non-point source pollution. Keep in mind that vegetation does not increase impervious surfaces, and it typically increases evapotranspiration rather than reducing it.