Man’s Effect on the Environment Freshwater Environments : Man pollutes freshwater all over the world in many ways there is much waste and pollution that ends up in rivers. One of the main hazards is called eutrophication, this process becomes enriched with artificial nutrients from fertilisers which run off into the rivers and upset the natural nutrient cycle of the river, lake or pond. The water turns green because of the algae which when they die multifly using up all the oxygen. Similar consequences occur if raw sewage is pumped into a ....