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Saturday, May 14, 2011

Overpopulation and Extinction

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The world’s human population doubled from 1 to 2 billion between 1800 and 1930, and then doubled again by 1975. Sometime in 2011, it’s expected to top 7 billion. This staggering increase and the massive consumption it drives are overwhelming the planet’s finite resources. We’ve already witnessed the devastating effects of overpopulation on biodiversity: Species abundant in North America two centuries ago — from the woodland bison of West Virginia and Arizona’s Merriam’s elk to the Rocky Mountain grasshopper and Puerto Rico’s Culebra parrot — have been wiped out by growing human numbers.
As the world’s population grows unsustainably, so do its unyielding demands for water, land, trees and fossil fuels — all of which come at a steep price for already endangered plants and animals. Most biologists agree we’re in the midst of the Earth’s sixth mass extinction event; species are disappearing about 1,000 times faster than is typical of the planet’s history. This time, though, it isn’t because of geologic or cosmic forces but unsustainable human population growth.
Today’s global human population stands at 6.9 billion. Every day, the planet sees a net gain of roughly 250,000 people. If the pace continues, we’ll be on course to reach 8 billion by 2020 and 9 billion by 2050.

We’re in the midst of the Earth’s sixth mass extinction crisis. Harvard biologist E. O. Wilson estimates that 30,000 species per year (or three species per hour) are being driven to extinction. Compare this to the natural background rate of one extinction per million species per year, and you can see why scientists refer to it as a crisis unparalleled in human history.

The current mass extinction differs from all others in being driven by a single species rather than a planetary or galactic physical process. When the human race — Homo sapiens sapiens — migrated out of Africa to the Middle East 90,000 years ago, to Europe and Australia 40,000 years ago, to North America 12,500 years ago, and to the Caribbean 8,000 years ago, waves of extinction soon followed. The colonization-followed-by-extinction pattern can be seen as recently as 2,000 years ago, when humans colonized Madagascar and quickly drove elephant birds, hippos, and large lemurs extinct.

The first wave of extinctions targeted large vertebrates hunted by hunter-gatherers. The second, larger wave began 10,000 years ago as the discovery of agriculture caused a population boom and a need to plow wildlife habitats, divert streams, and maintain large herds of domestic cattle. The third and largest wave began in 1800 with the harnessing of fossil fuels. With enormous, cheap energy at its disposal, the human population grew rapidly from 1 billion in 1800 to 2 billion in 1930, 4 billion in 1975, and 6.8 billion today. If the current course is not altered, we’ll reach 8 billion by 2020 and 9 to 15 billion (likely the former) by 2050.
No population of a large vertebrate animal in the history of the planet has grown that much, that fast, or with such devastating consequences to its fellow earthlings. Humans’ impact has been so profound that scientists have proposed that the Holocene era be declared over and the current epoch (beginning in about 1900) be called the Anthropocene: the age when the “global environmental effects of increased human population and economic development” dominate planetary physical, chemical, and biological conditions.
·         Humans annually absorb 42 percent of the Earth’s terrestrial net primary productivity, 30 percent of its marine net primary productivity, and 50 percent of its fresh water.
·    Forty percent of the planet’s land is devoted to human food production, up from 7 percent in 1700.

·       Fifty percent of the planet’s land mass has been transformed for human use.
· More atmospheric nitrogen is now fixed by humans that all other natural processes combined.
Key Words : over population, food production, land mass
- Center for Biological Diversity http://www.biologicaldiversity.org

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