Final answer:
The overuse of fertilizers containing nitrogen and phosphorus can cause eutrophication in water bodies, leading to excessive aquatic plant growth, oxygen depletion, and the creation of dead zones harmful to aquatic life and potentially humans.
Step-by-step explanation:
Impact of Fertilizer Runoff on Biodiversity
Human activity, particularly in agriculture, can release nitrogen and phosphorus into the environment through the use of artificial fertilizers. The excessive use of these fertilizers leads to a phenomenon known as eutrophication. When fertilizers are washed off fields by rain or irrigation, they enter nearby bodies of water, leading to nutrient pollution. This pollution stimulates the overgrowth of algae and other aquatic microorganisms. The dense algal blooms block sunlight from reaching deeper water and clog waterways, which significantly disrupts the ecosystem. After the algae die, their decomposition depletes the water of dissolved oxygen, which aquatic animals, such as fish and shellfish, need to survive. This creates anoxic, or oxygen-depleted, conditions often resulting in 'dead zones' where few aquatic organisms can live. The detrimental effects of eutrophication on aquatic systems can extend up the food chain, potentially affecting human health as well.
Aside from the direct effects on aquatic environments, excess nitrogen from fertilizers can contribute to the formation of greenhouse gases and acid rain when combined with the combustion of fossil fuels. These broader environmental impacts can contribute to climate change and negatively affect both terrestrial and aquatic ecosystems.