environmental contamination by humans

All life on Earth depends on water. Contamination of rivers, lakes, seas, and precipitation poses serious environmental problems. Human activity is threatening quality of water. The burning of fossil fuels releases air-polluting compounds and large amounts of carbon dioxid into the atmosphere. The chemical reactions of these compounds with water alter the delicate balance of conditions for life by affecting water pH. Acid precipitation has killed fish and damaged other forms of life in lakes and streams, and it also changes soil chemistry and has negatively affected some forests. Major product of fossil fuel combustion is carbon dioxide which stays in the atmosphere. Some carbon dioxide is taken up by plants for their photosynthesis and about 30% is absorbed by the oceans. An increase of carbon dioxide is expected to change ocean chemistry and harm marine life and ecosystems.