Explain why biodiversity is important for the survival of species, including humans. How could the destruction of the rainforest, and its biodiversity, affect people living in the United States?
Rainforests now occupy less then ½ of the land that they did 100 years ago (that’s less than 2% of the earth’s surface).
The major causes of biodiversity decline are land use changes, pollution, changes in atmospheric CO2 concentrations, [ changes in the nitrogen cycle and acid rain, climate alterations, and the introduction of exotic species, all coincident to human population growth. For
rainforests, the primary factor is land conversion. Climate will probably change least in tropical regions, and nitrogen problems are not as important because growth in rainforests is usually limited more by low phosphorus levels than by nitrogen insufficiency. The introduction of exotic species is also less of a problem than in temperate areas because there is so much diversity in tropical forests that newcomers have difficulty becoming established (Sala, et al., 2000).
a. Human population growth: The geometric rise in human population levels during the twentieth century is the fundamental cause of the loss of biodiversity. It exacerbates every other factor having an impact on rainforests (not to mention other ecosystems). It has led to an unceasing search for more arable land for food production and livestock grazing, and for wood for fuel, construction, and energy. Previously undisturbed areas (which may or may not be suitable for the purposes to which they are constrained) are being transformed into agricultural or pasture land, stripped of wood, or mined for resources to support the energy needs of an ever-growing human population. Humans also tend to settle in areas of high biodiversity, which often have relatively rich soils and other attractions for human activities. This leads to great threats to biodiversity, especially since many of these areas have numerous endemic species. Balmford, et al., (2001) have demonstrated that human population size in a given tropical area correlates with the number of endangered species, and that this pattern holds for every taxonomic group. Most of the other effects mentioned below are either consequent to the human population expansion or related to it.
The human population was approximately 600,000 million in 1700, and one billion in 1800. ]
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