Many commercially important fish populations, once thought to be inexhaustible, have declined drastically by overfishing. In 2015, 33% of marine fish stocks are being harvested at unsustainable levels. North Atlantic bluefin tuna population decreased by 80% in just ten years, spurred by high demand and high prices.

Overharvesting stems from several factors, including an exponential increase in the human population, expanding markets, increasing demand and improved access and techniques for capture.

When humans harvest wild animals at rates that are faster than what their populations can recover, this is referred to as overharvesting.

waste matter from homes and industries

Untreated sewage should not be discharged into rivers or lakes as it may contain disease-causing bacteria. If these bacteria get into drinking water, they may affect a large number of people in the community with diseases e.g. cholera or typhoid causing an epidemic.

Eutrophication is a process where a water body (e.g. lake, river) receives excess nutrients like nitrates and phosphates. This causes excessive growth of algae and floating water plants.