school energy&environment

What is extinction?

Extinction is an evolutive process that leads to the disappearance of a species or a population. When a species becomes extinct, its entire genetic heritage is lost for good. With evolution, a species can become another in order to adapt to the small environmental changes or due to casual changes in its genetic heritage. This process is known as speciation, in other words the birth of a new species. Speciation and extinction are both part of the natural evolutive process of living beings. Therefore, the natural extinction of a species in itself must not be interpreted as a negative event (nor, obviously, as a positive event), but it must be considered simply for what it is, in other words, an expression of biological evolution. The great extinctions in history, in fact, were accompanied by the formation of new species that have given continuity and vigour to the diversities of life. Normally two types of extinction may be classified. There is the background extinction that is the slow and, for us, imperceptible trend of the living creatures to transform constantly. And then there is the episodic extinction, with massive and concomitant deaths of species, triggered by rapid changes in the environment. In general, the extinctions that contributed most to the drastic changes in the flora and fauna in the earth’s history, were of the second type. Some extreme events took place on a vast scale during the course of the geological eras, like climate changes or the impact of our planet with comets and asteroids, which translated into environmental perturbations that were so radical that there were not many possibilities of escape for a multitude of organisms. At various times of the Earth’s history, these phenomena have been very severe limiting factors for the survival of the species, and at times these have drastically cut biodiversity in entire geographic regions, causing the so-called mass extinctions. Palaeontology experts have discovered five great mass extinctions in the last 500 million years. From the famous one that led to the extinction of all the dinosaurs on the Earth. During these great extinctions it is believed that 75 per cent to 95 per cent of the number of extinct species is believed to have gone lost. However, today the extinction rate is not considered natural, but the main cause of it all appears to be mankind, that, according to some scientists will cause a sixth mass extinction. In fact approximately 23 per cent of the Mammals and 12 per cent of the Birds are considered to be endangered by IUCN (the International Union for Conservation of Nature). There seem to be a number of causes that lead to this rapid mass extinction, however they are all caused by humans: constant growth of human population with a non-sustainable life-style increase in urban areas increase in the production of waste and polluting substances increase in alien, non autochthonous species climate changes international conflicts.