A Warning Sign of a Mass Extinction Event Is On the Rise, Scientists Say

An anonymous reader quotes a report from Vice: If you live near a freshwater river or lake, odds are good that you have seen warning signs about harmful algal and bacterial blooms posted on its shores. Alarmingly, a new study reports that these blooms may be early indicators of an ongoing ecological disaster, caused by humans, that eerily parallels the worst extinction event in Earth's history. Some 251 million years ago, the end-Permian event (EPE), popularly known as the 'Great Dying,' wiped out nearly 90 percent of species on Earth, making it the most severe loss of life in our planet's history. Ominous parallels of that upheaval are now showing up on Earth, according to a team led by Chris Mays, a postdoctoral researcher and palaeobotanist at the Swedish Museum of Natural History in Stockholm. The researchers found that toxic algal and bacterial blooms during the Great Dying are similar to a recent microbial proliferation in modern lakes and rivers -- a trend that has been linked to human activities such as greenhouse gas emissions (especially carbon dioxide), deforestation, and soil loss.

The repeated correlation of these blooms with mass extinction events is 'a disconcerting signal for future environmental change,' report the researchers in a study published on Friday in the journal Nature Communications. Indeed, there's a lot of evidence to suggest we are currently in the midst of yet another mass extinction event, caused by humans. Not only do microbial blooms transform freshwater habitats into 'dead zones' that can both choke out other species, thereby increasing the severity of extinction events, they can also delay the recovery of ecosystems by millions of years, the team noted. Mays and his colleagues reached this troubling conclusion by analyzing fossil records near Sydney, Australia, that were laid down before, during, and after the end-Permian extinction.

Though the exact mechanisms behind the Great Dying are a matter of debate, it was driven in part by an intense bout of volcanic eruptions that sparked a dramatic uptick in global temperatures and greenhouse gases emissions. Wildfires, droughts, and other disruptions swept across the woodlands, causing a collapse of plant life and widespread deforestation. The sudden loss of forests, which act as a sink for carbon, created a noticeable 'coal gap' during the end-Permian that exposes this long-term interruption in carbon sequestration. Nutrients and soils that had once been metabolized by these botanical ecosystems instead seeped into nearby freshwater habitats, bolstering microbial blooms that were already thriving as a result of higher temperature and atmospheric carbon.

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