Biodiversity is defined as the total number of different species  present in an environment, the integrity of which is a direct indication.It is estimated that there are 5 to 30 million different plant and animal species on Earth, of which only 1.4 million have been described. Rainforests, although degraded by human activities, maintain one of the highest biodiversity values on the contrary, for example, a field cultivated with only one variety of cereals has a very low biodiversity.The decrease in biodiversity is caused by the extinction of species due both to natural causes and especially in the 1900s, to the action of man: many species have disappeared following indiscriminate hunting and more recently due to alterations of the natural environment and pollution.The worsening of environmental conditions.The alteration of the environment by man often leads to the destruction of many natural habitats due to both different forms of pollution and other types of disturbances, such as deforestation and overgrazing, which contribute to desertification, compromise the hydrogeological structure of the territory, the expansion of urban, industrial and agricultural settlements.Pollution is defined as the complex of alterations caused to the environment (atmosphere, water and soil) by agents that modify its chemical, physical or biological characteristics, generally in an unfavorable way to life. Although pollution phenomena may occur due to natural causes (for example, the emission of gases and ashes of volcanic origin), the term today refers mainly to the harmful alterations caused by the action of man, the species that more than any other is able to modify the environment.Pollutants are harmful to the environment both for their intrinsic toxicity and because they are released in doses that exceed the natural self-purification capacity of ecosystems.Pollutants are residues or by-products of industrial activity and agricultural and civil biological waste.The causes of pollution are linked to various interrelated factors, including demographic growth, progressive urban concentration and the consequent increase in needs and therefore in the production of consumer goods.The effects of continuous and uncontrolled pollution affect the growth rate and health of living species and interfere with food chains.