Question

2. Explain in a brief paragraph how human activities have affected the nitrogen cycle in both positive and negative ways.

Answer 1

Human activities have dramatically altered the nitrogen cycle in both beneficial and harmful ways. The Haber–Bosch process, widespread use of synthetic fertilizers, cultivation of nitrogen-fixing crops, and improved wastewater treatment have increased the supply of reactive nitrogen, greatly boosting agricultural productivity and food security. At the same time, excess nitrogen from fertilizers, animal manure, sewage, and fossil fuel combustion washes into rivers and coastal waters, causing eutrophication, harmful algal blooms and hypoxic “dead zones,” and contaminates groundwater with nitrates that pose health risks; increased emissions of nitrous oxide (N2O) also contribute to climate change and stratospheric ozone depletion. Thus human activities have increased available nitrogen with major societal benefits but have also created serious ecological and public‑health problems.