Which factor is crucial when considering fertilizer application in urban ecosystems?

When considering fertilizer application in urban ecosystems, nutrient runoff is a crucial factor because it directly impacts water quality and ecosystem health. Urban areas often have impervious surfaces like roads and pavements that prevent water from soaking into the ground, leading to increased surface runoff during rainfall. When fertilizers are applied, nutrients can wash off these surfaces and enter storm drains, ultimately reaching local waterways.

Excessive nutrient runoff, particularly nitrogen and phosphorus, can result in problems like algal blooms, which deplete oxygen in water bodies and harm aquatic life. Therefore, managing how and when fertilizers are applied in urban settings is essential to mitigate the risks of nutrient runoff and protect water resources.

While soil type, plant diversity, and the scale of urban development are important considerations in their own right, they do not have the same immediate relationship with water pollution concerns as nutrient runoff. Proper assessment and management of nutrient runoff can help enhance both the sustainability of urban ecosystems and the health of nearby water bodies.