human causes of extinction

other causes of extinction

In addition to habitat destruction, other human-caused problems are also threatening many species. These include issues associated with climate change, pollution, and over-population.

human overpopulation

Human populations are on the rise. The human population passed the 7 billion mark in October of 2011, and will pass 8 and 9 billion probably before the middle of the century. All these people will need resources such as places to live, food to eat, and water to drink, and they will use energy and create waste. Essentially, human population growth can effect all other causes of extinction. For example, more people on the Earth means more people contributing to global warming and pollution. More people also means more clearing of land for agriculture and development. Recall that development by humans often causes habitats to be destroyed. This destruction can force species to go extinct, or move somewhere else.


Pollution adds chemicals, noise, heat, or even light to an environment. This can have many different harmful effects on all kinds of organisms. For example, the pesticide DDT nearly eliminated the peregrine falcon in some parts of the world. This pesticide caused falcons to lay eggs with thinner shells. As a result, fewer falcon eggs survived to hatching. Populations of peregrine falcons declined rapidly. DDT was then banned in the U.S. and peregrine falcon populations have recovered. Water pollution threatens vital freshwater and marine resources throughout the world ( Figure 1.1). Specifically, industrial and agricultural chemicals, waste, and acid rain threaten water. As water is essential for all ecosystems, water pollution can result in the extinction of species. A bird that was the victim of an oil spill. About 58,000 gallons of oil spilled from a South Korea-bound container ship when it struck a tower supporting the San Francisco-Oakland Bay Bridge in dense fog in November, 2007. Finally, soil contamination can also result in extinction. Soil contamination can come from toxic industrial and municipal wastes ( Figure 1.2), salts from irrigation, and pesticides from agriculture. These all degrade the soil as well. As soil is the foundation of terrestrial ecosystems, this can result in extinction.


global warming

Another major cause of extinction is global warming, which is also known as global climate change. During the past century, the Earths average temperature has risen by almost 1C (about 1.3F). You may not think that is significant, but to organisms that live in the wild and are constantly adapting to their environments, any climate change can be hazardous. Recall that burning fossil fuels releases gasses into the atmosphere that warm the Earth. Our increased use of fossil fuels, such as coal and oil, is changing the Earths climate. Any long-term change in the climate can destroy the habitat of a species. Even a brief change in climate may be too stressful for an organism to survive. For example, if the seas increase in temperature, even briefly, it may be too warm for certain types of fish to reproduce.

instructional diagrams

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most current species extinction is because of humans.

-->  a. true

b. false

the size of the human population creates many issues relating to the survival of other species.

-->  a. true

b. false

the burning of fossil fuels

a) changes the habitats of many species.

b) warms the planet.

c) can lead to species extinction.

-->  d) all of the above


-->  a) changes the habitats of many species.

b) comes from greenhouse gases.

c) leads to species population increases.

d) all of the above

if nothing changes from today, human population increases will result

a) more greenhouse gases emitted.

b) additional species extinction.

c) more habit destruction.

-->  d) all of the above

threats to soil include

a) damage from greenhouse gases.

-->  b) damage from agricultural pesticides.

c) damage from acid rain.

d) all of the above

threats to water include

a) damage from greenhouse gases.

b) damage from agricultural pesticides.

-->  c) damage from acid rain.

d) all of the above

diagram questions

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