A person changes environmental conditions, polluting it, occupying the natural habitats of plant and animal species, and they are forced to adapt to new conditions, changing their gene pool. Those who do not succeed die out. Man changes his home species purposefully, selecting specimens with those qualities (arising from natural mutations) that are necessary.
The main task of nature conservation is to protect the gene pool – the totality of genes that are found in all individuals in populations. Changes in the gene pool occur due to mutations caused by natural factors and factors of anthropogenic origin. Destruction, extermination of individual species of the population impoverishes the gene pool of the planet, which currently has about 1.3 million species of animals only. Of the 300 thousand species of higher plants of the world flora, only about 2.5 thousand are constantly used in agriculture, and 20 thousand – as needed.
The reduction in the number of species of animals under the influence of economic activity of people began a very long time ago, but especially intensified in the era of the scientific and technological revolution. At the same time, the rate of extinction of animal species has steadily increased, and with particular swiftness in the last one and a half to two centuries.
It is easy to imagine the main reasons for the supercritical decline in the number of species, which led to their extinction when conditions change. This is, first of all, the reduction of habitats, providing the whole complex of environmental factors that determine the possibility of the existence of a species. The limiting factor, depending on the biological properties of the species, could be the direct impact of changes in climatic conditions and physico-chemical characteristics of the habitat. It could be any biotic factor, for example, a sharp reduction in the number of main fodder plants or, for a predator, ordinary hunting objects. An important factor could be the emergence of a competing species, better adapted to survive in worsened conditions.
With the same result – reducing the number to a critical level and lower – factors associated with human activity are now operating with increasing efficiency. They are called man-made, from the Greek “anthropos” – man. Anthropogenic factors act both directly and through a change in the properties of the natural environment. Thus, habitat reduction occurs mainly due to the economic development of new territories – deforestation, plowing, expansion of the territories used for pasture and increasing pasture load, construction of new towns and cities, expansion of road and other communication networks. In addition, significant territories and large bodies of water, especially inland seas, lakes and rivers, are so altered by the accumulation of harmful substances that they become unsuitable for many species.