the overall population of a species decreased. what could have occurred to make this happen? brainly

Homo Population Growth and extinction

We're in the midst of the Earth'southward 6th mass extinction crisis. Harvard biologist E. O. Wilson estimates that 30,000 species per year (or iii species per hour) are existence driven to extinction. Compare this to the natural background rate of ane extinction per one thousand thousand species per year, and you can see why scientists refer to it equally a crisis unparalleled in homo history.

The current mass extinction differs from all others in being driven past a unmarried species rather than a planetary or galactic physical procedure. When the homo race — Homo sapiens sapiens — migrated out of Africa to the Center Due east 90,000 years agone, to Europe and Commonwealth of australia 40,000 years agone, to Due 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 every bit recently as 2,000 years ago, when humans colonized Madagascar and apace drove elephant birds, hippos, and big lemurs extinct [1].

Lange's metalmark butterfly from Amy Harwood.

The commencement wave of extinctions targeted big vertebrates hunted by hunter-gatherers. The 2nd, larger wave began 10,000 years agone as the discovery of agriculture caused a population boom and a need to turn wild animals 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, inexpensive energy at its disposal, the human population grew rapidly from 1 billion in 1800 to ii billion in 1930, 4 billion in 1975, and over 7.5 billion today. If the current course is not altered, we'll reach 8 billion past 2020 and nine to 15 billion (likely the sometime) by 2050.

No population of a big vertebrate animal in the history of the planet has grown that much, that fast, or with such devastating consequences to its young man earthlings. Humans' bear upon has been so profound that scientists have proposed that the Holocene era be alleged over and the electric current epoch (beginning in about 1900) be called the Anthropocene: the age when the "global environmental furnishings of increased homo population and economical development" boss planetary physical, chemical, and biological weather [2].

• Humans annually absorb 42 pct of the Earth'south terrestrial net primary productivity,30 per centum of its marine cyberspace primary productivity, and 50 percent of its fresh water [iii].
• Xl percent of the planet'southward land is devoted to man food production, up from 7 per centum in 1700 [3].
• 50 percent of the planet's land mass has been transformed for human use [three].
• More atmospheric nitrogen is now fixed past humans than all other natural processes combined [three].

The authors of Human Domination of World's Ecosystems, including the electric current director of the National Oceanic and Atmospheric Assistants, ended:

"[A]ll of these seemingly disparate phenomena trace to a unmarried cause: the growing scale of the human being enterprise. The rates, scales, kinds, and combinations of changes occurring now are fundamentally dissimilar from those at any other time in history. . . . We live on a human-dominated planet and the momentum of human population growth, together with the imperative for further economic development in most
of the world, ensures that our dominance will increase."

Predicting local extinction rates is complex due to differences in biological diversity, species distribution, climate, vegetation, habitat threats, invasive species, consumption patterns, and enacted conservation measures. One abiding, yet, is human being population pressure. A report of 114 nations found that human population density predicted with 88-pct accuracy the number of endangered birds and mammals as identified by the International Matrimony for the Conservation of Nature [iv]. Current population growth trends signal that the number of threatened species will increment past 7 pct over the next 20 years and 14 percent past 2050. And that'southward without the addition of global warming impacts.

When the population of a species grows beyond the capacity of its environs to sustain it, it reduces that capacity below the original level, ensuring an eventual population crash.

"The density of people is a key cistron in species threats," said Jeffrey McKee, one of the study's authors. "If other species follow the same pattern as the mammals and birds... we are facing a serious threat to global biodiversity associated with our growing human population." [5].

Then where does wild fauna stand up today in relation to 7.5 billion people? Worldwide, 12 percentage of mammals, 12 percent of birds, 31 percent of reptiles, 30 pct of amphibians, and 37 percent of fish are threatened with extinction [6]. Non enough plants and invertebrates accept been assessed to determine their global threat level, but it is severe.

Extinction is the most serious, utterly irreversible outcome of unsustainable homo population. Simply unfortunately, many analyses of what a sustainable human population level would look similar presume that the goal is simply to proceed the man race at a level where it has enough food and clean h2o to survive. Our notion of sustainability and ecological footprint — indeed, our notion of earth worth living in — presumes that humans volition permit for, and themselves enjoy, plenty room and resources for all species to alive.

REFERENCES CITED

1. Eldridge, N. 2005. The Sixth Extinction. ActionBioscience.org.
2. Crutzen, P. J. and E. F. Stoermer. 2000. The 'Anthropocene'. Global Change Newsletter 41:17–18, 2000; Zalasiewicz, J. et al. 2008. Are We At present Living in the Anthropocene?. GSA Today (Geological Gild of America) 18 (2): 4–8.
3. Vitousek, P. M., H. A. Mooney, J. Lubchenco, and J. M. Melillo. 1997. Man Domination of Earth's Ecosystems. Scientific discipline 277 (5325): 494–499; Pimm, Due south. L. 2001. The World According to Pimm: a Scientist Audits the World. McGraw-Hill, NY; The Guardian. 2005. World is All Out of New Farmland. December 7, 2005.
4. McKee, J. G., P. West. Sciulli, C. D. Fooce, and T. A. Waite. 2004. Forecasting Biodiversity Threats Due to Human Population Growth. Biological Conservation 115(one): 161–164.
5. Ohio State University. 2003. Anthropologist Predicts Major Threat To Species Within fifty Years. ScienceDaily, June 10, 2003.
6. International Union for the Conservation of Nature. 2009. Red Listing.

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Source: https://www.biologicaldiversity.org/programs/population_and_sustainability/extinction/

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