Extinction of species is a natural process that has occurred since the beginning of life on earth. Organisms most suited to the current environmental conditions survive and reproduce whereas those less poorly suited either do not survive or contribute little or nothing to the genetic capital of the next generation. This process is known as natural selection or survival of the fittest. Anthropogenic influences on this process, especially in the last century has effected this process through habitat or ecosystem conversion and the input of pollution in the air, water and soil (text book, year).
For example, the input of nutrients (nitrogen and phosphorus) to water bodies can result in a change of the species dynamics resulting in algal blooms (phytoplankton that thrive on high levels of nutrients in the water). When these blooms of phytoplankton die, bacteria decompose them and use up all the oxygen in the water. This starves the other members of the aquatic community of the oxygen they need to live and they suffocate. These areas, such as the Gulf of Mexico, the Great Lakes, and the Baltic and Black Seas are examples of these “dead zones.” High influxes of nutrients are due to excess fertilizers running off into a water body due to farming and land conversion practices (text book, year).
Another example of high extinction rates due to human activities is the high extinction rates of freshwater animals in North America. Since 1900, over 123 species have gone extinct. This rate is five times faster than the extinction of terrestrial species. It is estimated that an additional 4% of freshwater species in North America will go extinct per decade which rivals the extinction rates in the very biologically diverse tropical rainforests (Riciardi & Rasmussen, 1999).
Historically, habitat conversion has occurred randomly by natural processes. Human activity however, has now resulted in nonrandom and accelerated patterns of habitat change. Anthropogenic habitat conversion is at an all-time maximum and it is still increasing. As habitats are converted to human use (agriculture and development), extinction levels will increase. Conservation efforts in the US have focused on high elevation, wilderness areas, but most habitat conversion is occurs in low-lying areas which contain 90% of the biodiversity (Seabloom, Dobson, & Stoms, 2002).
Protection of biomes are also important. For example, boreal forests have high biodiversity and now make up almost one-third of all remaining global forests. Human disturbances to this fragile ecosystem have resulted in increases in habitat fragmentation and loss of biodiversity in these ecosystems. Also, the boreal forests play a very important role as a “carbon sink” by absorbing large amounts of the ever increasing levels of carbon dioxide out of the atmosphere and concentrating it into plant mass. These important forests act as a “sponge” to soak up the extra carbon dioxide contributing to global climate change (Bradshaw, Warkentin, & Sodhi, 2009).
References
Bradshaw, C. J. A., Warkentin, I. G., & Sodhi, N. S. (2009, Oct.) Urgent preservation of boreal carbon stocks and biodiversity. Trends in Ecology & Evolution, 24(10), 541-548.
Ricciardi, A. & Rasmussen, J. B. (1999, Oct.) Extinction rates of North American freshwater fauna. Conservation Biology, 13(5), 1120-1222.
Seabloom, E. W., Dobson, A. P., & Stoms, D. M. (2002, Aug. 20). Extinction rates under nonrandom patterns of habitat loss. PNAS, 99(17), 11229-11234.
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