Environmental Hazards

Loss of habitat is the principle threat to the survival of endangered plants and animals. Large areas of important natural habitat have been already lost, including 70 percent of the forests in Greece, 91 percent of the moist forests in Sudan, and nearly 100 percent of the tall grass prairies in the United States. Population growth, agricultural expansion, the raising of cattle and other livestock, the building of cities and roads and pollution are among the many causes of habitat distraction. “National Protected Systems” make up 3,7 percent of the Earth’s land area, but the amount of land protected in each country varies from a high of 38 percent in Ecuador to less than 1 percent in Turkey. Both the number and size of “International Protection Systems” have increased over the years, but legal protection does not guarantee actual protection of the land.

Information about wildlife at risk in some courtiers is not always available. For instance, little is known about non-mammals in Africa and about Asian species in general. For some countries, however, information is readily available. For example 43 mammalian species in Australia and 123 bird species in Mexico are at risk, 18 amphibian species in France are threatened with extinction.

Trade in animals and animal products can have disastrous effects on wildlife populations. Some bird species have become endangered solely from being hunted for the pet trade. Much of the trade in animals and animal products is illegal. Many rare birds are taken illegally from their habitat, and the ivory trade has reduced the total elephant population in Africa from an estimated 1.300.000 in 1979 to fewer than 650.000 today.

When we think of wildlife facing extinction, we are usually thinking of large majestic animals such as whales, elephants and rhinos or the “cuddly” black-and-white panda. These creatures are indeed at risk of extinction because of irresponsible and cruel hunting by human predators. But the threat of extinction is not limited to the few species that we can recognize in pictures or visit in zoos. The threat of extinction affects almost every species on earth, down to the tiniest microbe.

The balance of nature within any ecosystem depends on the complex interaction between millions of species of animals, plants and microorganisms. The death of one species could threaten the survival of hundreds of others. A second species might lose its food supply. Another species could lose its predators, so it might become more numerous. The populations of parasites and microorganisms that depend on these larger species will also change. This may lead to the spread of new diseases in the higher organisms. There are many more species of small organisms then of large ones. Insects outnumber all other animal species combined, and bacteria outnumber all the animal and plant species together. Microorganisms influence important physical properties such as the acidity and mineral content of the soil, the salinity of the sea, and the amount of oxygen and carbon dioxide in the air. Changes in the populations of microorganisms may, therefore, cause major changes in the composition of the earth and its atmosphere.