The term biodiversity refers to both the variety and variability in species and the genes that they contain. The term biosphere is a more inclusive term used to define the parts of the Earth that these species inhabit. Both biodiversity and the biosphere are vanishing on Earth. The rate of species extinction has a significant impact on society, as well as on the entire biosphere. For example, genetic diversity better enables species to adapt to changing environmental conditions. Species diversity is the key to such fundamental ecological concepts as the food web and ecosystem stability. Generally, the most-complex ecological communities, which are composed of many different species, are the most stable and therefore the most resistant to bioecological change. Simpler ecological communities are more fragile, being less able to withstand changes and survive.

Most scientists estimate that as of 1997, there are approximately fifteen to twenty million species on Earth. This rich variety of living things that exists on this planet is ultimately the source of society's food, clothing, shelter, and more. Natural ecosystems continually recycle air, water, and land. Society disrupts biodiversity by minimizing its options and quality of life.

In the biosphere, species are challenged by fluctuations in the physical environment, predation, parasitism, and competition for resources. Extinction results when species, highly adapted to one set of conditions, are unable to survive under new conditions. The history of the dinosaur attests to the eventual fate of many organisms--extinction. Since the origin of life, three to four billion years ago, researchers have estimated that 99 percent of all species that once existed have disappeared. This is because living organisms were unable to adapt to changes in the biosphere.

Although extinction is a natural biological process, it has been increasing at an alarming rate since the 1600s. Approximately 150 mammals and birds have become extinct, following the patterns of the dodo bird, passenger pigeon, dusky seaside sparrow, eastern elk, plain wolf, and the Leon springs pupfish. Several scientists have predicted that by the end of the twentieth century, approximately one million of the world's species will vanish, and that another 30-50 percent will become extinct within five hundred years. Some pessimistic estimates suggest that extinction rates for all taxonomic species will be one to three species per hour.

The overwhelming rate of species extinction is mainly the result of the expansion of the human population, along with trophy hunting, economic harvesting, deforestation, wetland drainage, urbanization, agricultural clearing, pollutants, and the introduction of intrusive species into various ecosystems. Humanity is changing the environment and destroying the natural habitats too rapidly for most flora and fauna to adapt.

In the past, due to the open country and the vast amount of biosphere, the thought of the biosphere as a finite resource was inconceivable. However, as the world now enters into the twenty-first century, recognitions of serious problems have called into question the carrying capacity of the biosphere that must support the world's human population. One of these problems is desertification, the process of converting arid and semiarid lands into veritable deserts. At the present pace of conversion, desertification could enormously decrease high agricultural productivity in both irrigated and non-irrigated lands. Desertification could also seriously decrease the carrying capacity of the lands that support human settlements and wildlife.

A second concern is the global trend of converting natural forest biomes to agricultural areas, urban centers, water resources, transportation, and other developments. If this trend continues, the number and size of natural forest biomes (tropical, deciduous, and coniferous forests) may be seriously reduced, thus eliminating the habitat that supports most of the growth of green plants, which in turn provide food either directly or indirectly to all living things. . .

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