There is no clear way of determining the total impact that humans are making on biodiversity; however, it is obvious that many actions by humans are causing a decrease in biodiversity. To determine the total impact that humans are making on a given environment, the area of productive land and water needed to produce the item that is being consumed and the need to account for the waste being generated by humanity must all be taken into account according to management and production practices in use during that time (Wackernagel et al., 2002).
Direct or indirect actions by humans have resulted in the decrease of biodiversity. The Convention of Biological Diversity states that there are both indirect and direct human drivers. Some of the indirect human drivers are demographic, economic, sociopolitical, scientific and technological, and cultural and religious factors. Some of the direct human drivers are changes in local land use and land cover, species introductions or removals, external inputs, harvesting, air and water pollution, and climate change (Climate, 2005).
Human activity has substantially changed one-third to one-half of the world’s surface (Frequently, 2005). In the next 50 years it is expected that humans will seriously impact 50-90 percent of land in developing countries. This is a result of growth in population and in over consumption of natural resources (Mapping, 2005). The population of humans is, what many consider, the root of the biodiversity problem (Eldredge, 2000). The number of humans on earth, as of July 2005, is at 6.4 billion (World, 2005). The increase in human inhabitants causes a problem because with it comes a need to convert natural habitats to land for human consumption.
One way that the humans have been able to sustain their growth is by converting natural habitats to fields where foods can be produced. At least 23 percent of the earth’s land is being used for agriculture (31 percent of all land is unfarmable). In the United States there is a direct relationship between the loss of forests to the increase in cropland (Dobson, 1996). Internationally, there is half a hectare of tropical forest disappearing to farmland every second. One of the potential dangers of decreasing the amount of natural habitats remaining is that species will no longer be present on earth. This directly affects agriculture because many of the species that are being destroyed for croplands may have been used for genetically enhancing crop products (Frequently, 2005). In this manner, the increase in agricultural land actually harms our agricultural future.
Human actions have also played a role in climate change, which is also causing great danger for biodiversity. The change in climate is due to increased atmospheric concentrations of carbon dioxide, which causes increased land and ocean temperatures, and changes in precipitation and sea level rise. With the change in climate also comes a change in species. Climate affects the timing of reproduction and migration, the length of growing seasons, species distributions and population size, and the frequency of pest and disease outbreaks. It is also expected that the change in climate in the 21st century will have a much higher rate than the past 10,000 years and create an even bigger impact on biodiversity (Climate, 2005). It is expected that 80 percent of biologically rich regions will suffer great losses of plant and animal species because of global warming. The rate of change of habitats is expected to increase up to ten times due to global warming (Sherbinin, 2002).
