We are currently facing Earth's sixth mass extinction – nice one, humans. So, researchers have looked at the world's previous mass extinctions to catch a glimpse of what the planet's biodiversity looks like after these cataclysmic events. It turns out, it's unsurprisingly depressing, at least in the short-term.
Mass extinctions obliterate much of the world's biodiversity, leaving many ecological niches vacant and ready to be filled by other organisms. As past events have shown, this leads to a long period where the land is overrun by weed-like “disaster fauna", along with a small selection of surviving and newly-evolving vertebrates.
These insights come from a new study published in the journal Nature Communications that looked at two of Earth’s past dramatic mass extinctions. An international team of scientists analyzed the fossil records of nearly 900 animal species from approximately 175 million to 260 million years ago, between the late Permian and Early Jurassic periods.
This length of time included the Permian-Triassic extinction event about 252 million years ago, one of the largest known extinction events which killed 96 percent of all sea species and 70 percent of land-dwelling vertebrate species.
“Mass extinctions not only reduced animal diversity, but also affected the distribution of animals and ecosystems, or biogeography,” explained study author David Button, a postdoctoral scholar at North Carolina State University and North Carolina Museum of Natural Sciences.
“As species are removed by extinction, their ecological niches are left vacant. Following the extinction event, these niches are occupied by surviving and newly evolving ‘weedy’ species. These few generalists spread out and dominated for a time, leading to a low-diversity global ‘disaster fauna.’”
The world doesn't remain a desolate land of “disaster fauna” forever, however. Mass extinction events initially wiped out many major groups of organisms but they also helped set the stage for a whole new entourage of all things great and small. For example, the Permian event removed many groups but, in doing so, allowed new groups to evolve, including the earliest dinosaurs, crocodiles, relatives of mammals, and lizards. Many dinosaurs also emerged to fill the void left by the end-Triassic event.
The world is currently entering a mass extinction event the likes of which have not been seen on Earth for at least 65 million years. This is primarily driven by human activity, in the form of deforestation, poaching, culling, hunting, pollution, loss of habitat, introducing invasive species, and climate change. Through broadening our understanding of these previous events, the researchers believe their findings could help ward-off the new sixth mass extinction event before it's too late.
“Further understanding of these ancient crises will help to inform conservation efforts to prevent modern animals from suffering a similar fate,” Button added.