Causes for the extinction of animals
The extermination of many populations due to the paving of its habitats is happening continuously in the entire planet. In 1880, the Brown butterfly of Sthenele disappeared completely under the city in growth of San Francisco, California. In 1943, the last one of the small blue butterfly of Xerces (Glaucopsyche xerces) was captured; its extinction also had to do with the growth of San Francisco whom its sand dune habitat occupied. This butterfly is remembered in the name of the Xerces Society (external liaison), that is an organization dedicated to the preservation of insects and other invertebrates in danger.
A very important portion of the world is being urbanized more and more as time passes. It is predicted that by the year 2025, 63% of Eastern Asia will be urbanized, Latin America 85%, and Africa 54%. Unless the correct steps are taken to control the suburban growth, much more populations and species are going to disappear under plates of concrete of a city in the next half century. Such species as the Chicken of the Prairies of Atwater (cupido Tympanuchus attwateri), that lived in the vicinities of Houston, Texas (the United States), will disappear due to a greater human expansion.
The urbanization also eliminates complete ecosystems since it tends to happen in areas that are as biologically rich as productive for agriculture. Usually the plants and the animals are attracted by those areas that have sufficient water and the climate is moderate. Generally, the people tend to be based in similar places. Therefore, the damage of the urbanization tends to concentrated on rich areas on species.
One of the richest areas in species of the world is the Province of Cabo in South Africa, but the great population explosion that is happening there is increasing the population in 60,000 people per month.
Time back, the shining yellow flowers, from the Golden Gladiolus (Gladiolus aureus) covered a valley and the hill near the City of Cabo. But strange plants, introduced to a claim program of dune, escaped and affect the population of gladiolus; soon it was followed by a habitational project, paving most of the rest of the habitat of the species, and the plants that managed to survive were confined to a wide land band of 10 meters and 40 meters in length. Then they were devastated to obtain gravel. Surprising, the few survivors were saved to be located between two rocky banks, but other factors - a road, places of picnic, swings for children, broken tins of beer, glasses, and others - still put more pressure. In 1979 there were hardly 113 plants of gladiolus left and in 1980 hardly 45; only two of them bloomed, and one was cut! The future of the species is seen very gray.
Other factors also affect the plants and the wild life. The road networks that connect urban areas have impacts on the animals as soon as its construction is finished. The roads serve like barriers to the movement, separating herds of the great animals or avoiding making the necessary seasonal migrations. The construction of a pipe line in Alaska caused serious problems to the movement of the caribous and other wild life.
The smallest animals also undergo divisions of their populations because of the highways and channels. These divisions change the population structure and cause the smallest populations to be less and more vulnerable. A study indicated that a divided highway of four tracks can be equivalent, for the small animals, to a river the double of wide.
Also countless animals are killed by vehicles every day. When the frogs, toads and salamanders of Central Europe cross the highways, migrating towards lakes and streams where they reproduce, million are squashed. This problem is so well known that the authorities have constructed fences to maintain them remote of the highways. The Swiss Association of Civil Engineer published instructions recently to construct passages of level for amphibians! Luckily for these creatures, the Swiss have learned the value of their population of amphibians, a lesson that would not make any damage if many of us also learn it.