Scientists say the next mass extinction may already be under way.
A new study, published in the most recent issue of the journal Nature states just that. And it's man-made.
The theory comes from research done on the state of mammal species today. When man's exponential expansion began 500 years ago mammal extinctions were rare.
But in the past five centuries at least 80 of 5,570 mammal species have gone extinct, according to AFP.
While the number may not seem too large, it could signify the beginning of a larger trend in extinctions.
There have been five previous mass extinctions in the past 540 million years. In each of those mass extinctions 75 percent or more of all animal species were destroyed.
The study also looked at a number of plant and animal species that will likely see a decline in the near future.
From USA Today:
The IUCN lists 18,351 species on its "Red List of Threatened Species," considered the global standard for the conservation status of animal and plant species. All are at risk based on current and projected habitat loss or destruction due to human encroachment and climate change. Of those, 1,940 are listed as critically endangered, meaning the species' numbers have decreased, or will decrease, by 80% within three generations.
However, it's still too early to definitively deem this the next mass extinction. According to the study, the sixth mass extinction is only on track if things continue unabated.
Even unhindered, the magnitude of this mass extinction could take as long as 2,200 years to reach "Big Five" levels, according to USA Today. Or it could take as little as 300.
It's also important to note that it's not certain that many of the endangered species studied will, in fact, go extinct. In turn, the conclusions made based on the data were considered "cautious extrapolations," according to the researchers.