Current trends show that the extinction rate of life on Earth eventually will be a mass extinction event. The number of species that are hurtling toward extinction has led many ecologists to argue that we are in the middle of a sixth mass extinction.
The percentage of extinctions caused by global temperature increases will not be the same as a mass extinction event in the near future according to a new study.
There have been five major mass extinctions throughout Earth's 4.5 billion-year history, and scientists want to understand how climate change is affecting global diversity in ways that may be irreversible.
According to the Natural History Museum in London, during a mass extinction, a high percentage of global biodiversity is extinguished faster than it can be replaced. In order to understand what a normal extinction rate looks like, ecologists measure what is known as the "background rate" of extinction.
5% to 10% species extinctions in 1 million years correspond to the background rate. Kaiho told Live Science that a higher rate of extinction is a significant event.
More than half of Africa's primate were claimed by 'Lost extinction'.
David Storch, a professor in the Department of Ecology at Charles University in Prague who was not involved in the new study, said estimating the background rate of extinction can be difficult. The rate of extinction is two orders of magnitude higher than the normal rate.
Kaiho said that major mass extinctions result in more than half of the species loss. Minor mass extinction events took place more often. Kaiho argues in the new study that the current extinction rate can't be considered a mass extinction event because of climate change.
The last five mass extinction events were the Silurian extinction, the LateDevonian extinction, the Permian-Triassic extinction, and the Triassic-Jurassic extinction. Kaiho reported that these events have led to drastic changes in Earth's climate, such as changes in surface temperature, acid rain, ozone depletion, reduced sunlight, desertification, soil erosion and a reduction of oxygen in the ocean. Changes in atmospheric and ocean chemistry played a bigger role in extinctions than global warming or cooling did. Global warming can increase the ocean's acidity as well as the atmosphere's composition, but volcanic activity also plays a large role.
Climate change may not be the sole cause of the extinctions, but the rate of extinction may be the result of other global changes which happened at that time.
Prior mass extinctions were triggered by volcanic eruptions and the change in climate was caused by an asteroid impact. Kaiho believes that the speed of environmental change is more important than the magnitude of change in causing massive extinction rates.
To meet the definition of a mass extinction event, scientists need to observe the extinction of at least half of the species. Even though this magnitude of extinctions has not been observed yet, it doesn't mean it's not happening. Climate change is the cause of the sixth extinction. According to Kaiho's paper, extinction rates in the near future are unlikely to meet the definition of a major mass extinction event because of the gradual pace of climate change.
There is a question about what could cause humans to extinction.
Kaiho said that an increase in average global temperatures of 9 degrees Celsius is essential for major mass extinctions. Because the rate of species extinction changes in parallel with global surface temperatures, we will not see an abrupt and massive loss of species, but rather a slow and steady rate of species extinction in the near future.
The present rate of extinction is only an estimate and may be an incorrect one. According to a study published in the journal Biological Reviews, the number of species extinctions recorded is biased towards mammals and birds and ignores many other animals. According to David Storch, other human-driven actions such as habitat transformation and pollution, as well as overhunting and the introduction of non-native species, play a bigger role in driving the current rate of species extinction than rising average global temperatures.
It was originally published on Live Science
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