50 Interesting Pics That Show That “Nature Was Metal” Thousands And Millions Of Years Ago (New Pics)

In a general sense, a species is considered officially extinct when the last individual has passed away in the wild or captivity, says Mattison Shreero, paleontologist, geologist, and science communicator at Geosplore.

But when looking deeper, there are several types of extinction, Bethany Burke, vertebrate paleontologist and CEO of BKBONES, explains.

"We have extinct in the wild, or "EW," meaning that there are no longer any populations of an animal/plant to be found outside of captivity of curation. This might mean that there are many (or lone) animals of the species being cared for by humans in a facility, likely with the intention of reintroduction into a habitat."

Then there's functional extinction, which also falls under extinction in the wild, says Burke.

"Think of Northern White Rhinos. There were members of the species alive until recently, but they were both aging females. With no male DNA available to continue the species, the Northern White Rhino was considered extinct before the last rhino passed away."

Another type is extinction in the historical range, which means that there are still wild individuals of an animal, but the places they can be found have been drastically reduced.

"Jaguars once had a historical range that included American states like Arizona! Unfortunately, this is no longer the case, and the jaguar population of the United States is extinct, with no reported sightings deep into the Southwestern region since the mid-20th century," Burke further explains.

"Finally, we have the big one! 'True' extinction or 'EX.' A better term to use is 'total extinction.' This is classified by the death of the last living member of a species."

How certain creatures go extinct varies, but the main reason for it is a change in their environment/habitat loss, experts say.

"First, it's important to recognize that extinction is a normal process (what we call background extinction), just like death is a normal process. However, human activity has caused the rate of extinction to be 100-10000x higher than it should be (yes, up to TEN THOUSAND times the normal rate)," Dr. Jingmai O'Connor, associate curator of fossil reptiles, explains.

"Extinction happens when change occurs so fast that species cannot adapt/evolve to handle the new circumstances. All causes can be summarized into a single factor—human overconsumption. Humans consume (and waste) so much, and it has a huge impact on the environment as we destroy natural ecosystems for mines, logging, agriculture, housing, and more."

Our overconsumption results in pollution and climate change, too, which toxifies environments and destroys delicate temperature-dependent ecosystems like coral reefs, notes Dr. O'Connor.

"It's also k*****g us, by the way. Infertility and cancer rates are ever-increasing because this toxicity isn't just bad for other species, it's bad for us, as is destroying ecosystems and causing rampant extinction. No species can survive alone."

Burke and Shreero agree that the most devastating mass extinction event in Earth's history was the Permian–Triassic extinction that happened around 252 million years ago.

"This event, known as 'the Great Dying,' resulted in the loss of 90-96% of all species on a global scale and was likely caused by intense volcanism in Siberia and subsequent effects of that volcanism (ocean acidification, rising temperatures, and such—sound familiar?)," Shreero explains.

"Humanity has already begun walking down the path towards another extinction event such as this, except we're progressing these effects at an even faster rate than they occurred at the end of the Permian—and if that doesn't scare you, I don't know what will."

Meanwhile, Dr. O'Connor believes that the most devastating mass extinction event in Earth's history is happening right now.

"I would say that this current, 6th mass extinction is the worst. While we will never know its full extent (meaning what percentage of terrestrial and marine macro-organisms are wiped out), since we will likely be victims of our own short-sightedness, this is the only mass extinction caused by a non-geologic or extraterrestrial event (the 5th mass extinction was caused by an asteroid)," Dr. O'Connor says.

"It is the only mass extinction that can be blamed on a single species, and one that claims to be intelligent and conscious to boot. It is a real tragedy, but in an evolutionary sense, you could say that our high level of intelligence and consciousness are evolutionary traits that don't lend themselves to long-term survival, since we are the first to have these traits to such a degree, and we have done the worst possible things with them and will very likely drive ourselves to extinction."