Venomous Sharks Prove London's River Is No Longer 'Dead'

The Thames River was declared "biologically dead" in the late 1950s. But after decades of cleanup and conservation efforts and investments in sewage treatment, that's no longer the case. Indeed, the 215-mile waterway running through London is now home to hundreds of wildlife species, including seahorses, eels, seals, even venomous sharks, according to a report released Wednesday by the Zoological Society of London. It identifies 92 bird species and 115 fish species, with numerous sharks noted, including tope, starry smooth-hound, and spurdog. Spurdog sharks release venom, which can cause pain and swelling in humans, from spines in front of its dorsal fins, CNN reports.

The report found a slight decrease in the number of fish species identified in tidal areas of the river since the 1990s. It's not clear why, though the report does reference rising water temperatures due to climate change. Summer temperatures in some parts of the river have risen an average of 0.19 degrees Celsius (0.34 degrees Fahrenheit) annually since 2007, per the Washington Post. This "paints a worrying picture," according to CNN, as such changes can transform the ecosystem and its habitats, the report notes. Water levels—which the report notes also impact "species' lifecycles and ranges"—have been rising in some areas by 0.17 inches per year on average since 1990, the outlet notes.

There are also concerns related to pollution—from a mass of wet wipes covering 1,000 square meters, to microplastics flowing downstream at a rate of 94,000 pieces per second, to elevated nitrate levels triggered by industrial runoff and sewage, per the Guardian. "This report has enabled us to really look at how far the Thames has come on its journey to recovery ... and in some cases, set baselines to build from in the future," says the Zoological Society's Alison Debney. Engineers behind the Thames Tideway, a 15-mile underwater sewage tunnel to be completed in 2025, say it will capture 95% of the sewage that overflows from London's sewers before landing in the river. (More River Thames stories.)