According to a new study, the present rate of extinction of life on Earth does not yet constitute a major extinction event, but current trends indicate that it will eventually. Many ecologists claim that we are experiencing a sixth mass extinction due to the amount of species that are currently in danger of going extinct; however, we are just seeing the beginning, and it will probably get much worse.
A recent analysis suggests that, at least in the near future the percentage of extinctions brought on by climate change-related rises in global temperature won’t equal that of a significant mass extinction event.
Scientists study the five major mass extinctions that occurred during Earth’s 4.5 billion-year history to better understand how climate change is currently harming world variety in ways which may be irreversible.
According to the Natural History Museum in London, a mass extinction occurs when a significant portion of the world’s biodiversity disappears faster than it can be recreated. This occurs during a geologically little period of time, under 2.8 million years (opens in new tab). Ecologists measure what’s been known as the “background rate” of extinction to comprehend what a “normal” extinction rate looks like because species can go extinct for a variety of reasons, according to the study’s the only author Kunio Kaiho, a professor emeritus at Department of Earth Science at the Tohoku University in Japan.
“Species extinctions in 1 million years correlate to the background rate,” says Kaiho. Kaiho explained that a greater rate, such as “more than 10% species extinction in a small time period (e.g., hundreds of years), is a big occurrence.”
However, because fossil records frequently overrepresent larger, more numerous species, evaluating the background rate of extinction for previous epochs can be “really tricky,” according to David Storch, a professor in Department of Ecology at the Charles University in Prague who wasn’t involved in the new study. The pace of extinction today, however, is “approximately two orders of magnitude more than the average rate of extinction,” according to Storch.
More than 60 percent of species are lost during major mass extinctions, according to Kaiho. Minor mass extinction events, on the other hand, “occurred more frequently.” In a new study that was released on July 22 in the journal Biogeosciences, Kaiho makes the case that although climate change increases extinction rates, the current rate does not yet meet the strict criteria for a mass extinction event.
The Ordovician-Silurian extinction, which occurred just around 440 million years ago, Late Devonian extinction, which occurred approx 365 million years ago, the Permian-Triassic extinction, which occurred approximately 253 million years ago, the Triassic-Jurassic extinction, which occurred roughly 201 million years ago, and Cretaceous-Paleogene extinction were the previous 5 main mass extinction events (around 66 million years ago). According to Kaiho, these occurrences have also been linked to significant alterations in the Earth’s climate, including variations in surface temperature, acid rain, ozone depletion, decreased sunlight, desertification, soil erosion, and a decrease in ocean oxygen. However, Storch believes that rather than global warming or cooling, variations in atmospheric and oceanic chemistry were more significant in these extinctions.
“The rate of extinction may be a result of the other worldwide changes that occurred at that time,” Storch said of the most recent mass extinctions. “The climatic change reported during these extinctions may not be the only cause of the extinctions.”
Climate changes that followed previous mass extinctions were swift and severe because they were brought on by volcanic eruptions and, in the case of Cretaceous catastrophe, an asteroid strike. In the study, Kaiho makes the claim that, because “animals can relocate to survive during sluggish climate changes,” the rate of environmental change is more significant than the size of change alone in producing enormous extinction rates.
Scientists would have to see the extinction of 60 percent of species and 35 percent of genera for it to qualify as a catastrophic mass extinction event. However, the fact that an extinction of this size hasn’t been seen yet doesn’t imply it isn’t happening right now. In contrast to its predecessors, the 6th extinction is being caused by human-caused climate change. According to Kaiho’s paper, we are uncertain to witness extinction rates in the near future that fit the criteria for a major mass extinction event, but they may very well meet the criteria for a minor mass extinction because the pace of such climatic change is gradual rather than rapid and drastic.
According to Kaiho, “at least until 2500 in the worst scenario,” an increase in global temperatures of 9 degrees Celsius (16.2 degrees Fahrenheit) would be necessary for large mass extinctions to coincide with global warming. In the near future, we won’t witness an unexpected and massive loss of species, instead a slow and steady rate of species extinction that won’t result in the loss of 60% of the earth’s species, Kaiho authored in the study. This is due to rate of species extinction changes in linearly with changes in global surface temperatures.
Numerous ecologists have provided an essential qualification to these findings, stating that the current rate of extinction is simply an estimate and might be off. A study from January 2022, which was published in the journal Biological Reviews(opens in new tab), found that the number of species extinctions reported is greatly understated because it heavily favours mammals and birds while ignoring many invertebrates. According to David Storch, other human-driven activities such as habitat alteration due to deforestation as well as pollution, overhunting, and the introduction of non-native species are currently driving the current rate of species extinction much more so than increasing average global temperatures.