What is Extinction?

Study Notes

Extinction means that something no longer exists, applying to species of plants, animals, and even humans.
Extinction can be caused by natural or artificial processes that occur on Earth.
Dinosaurs are a popular example of extinction, becoming extinct after the Cretaceous extinction over 65 million years ago.

There are two main types of extinction: mass extinction and background extinction.
Mass extinction is a rare phenomenon that occurs when a major catastrophe happens, resulting in a sudden and sweeping event that kills a large number of species.
Background extinction is a natural process that occurs over a long period of time, resulting in the gradual decline and elimination of species from the Earth.

Mass extinction is an extremely rare phenomenon that has only occurred five times on Earth.
The five mass extinctions on Earth include: Ordovician-Silurian, Devonian, Permian ("The Great Dying"), Triassic, and Cretaceous.
Fossils are essential in learning about the mass extinctions of the past, allowing scientists to estimate the date range of the event and how the lives of the species still in existence were affected.

Background extinction, also called the normal extinction rate, is the natural evolution and elimination of species from the Earth over a long period of time.
The natural extinction rate is one species out of every one million species per year based on fossil records.
Factors contributing to background extinction include climate change and population control.

Human practices such as manufacturing, lumbering, and fishing all have a consequence within the ecosystems of Earth.
Pollution, habitat loss, and overhunting are major reasons that species increasingly face extinction.
Human activity has not always been linked to extinction, but in recent years, it has become a subject of discussion.
Deforestation, using more land, and dumping trash into landfills are major contributors to extinction.

75% of land has been adapted for human use, taking away habitat for other species.
33% of the land on Earth is used for farming and agriculture, taking away large amounts of habitat for indigenous species.
66% of oceans have been used for human development.
75% of Earth's freshwater resources have been used.
25% of pollution comes from greenhouse gas emissions.
Fertilizers used in farming are a large contributor to pollution.
Global warming and rising sea levels can partially be attributed to pollution.
5% of species would be affected by global warming if the Earth was heated just 2 degrees Celsius.
16% of species face the threat of extinction with the current global warming trajectory.