In 1957, sections of London’s River Thames were labeled ‘biologically dead’ by scientists due to severe oxygen depletion from decades of sewage and industrial waste. Roughly 70 years later, the waterway now hosts sharks, seals, seahorses, eels and diverse aquatic species. A January 2026 report by the Zoological Society of London confirms ongoing recovery. At least five shark species, including tope and starry smoothhounds, now frequent the estuary, which may serve as a nursery area. The Greater Thames Estuary held about 2,987 grey seals and 599 harbour seals in 2024, with grey seal counts rising since 2013 monitoring began. Seals have been observed as far upstream as central London and Richmond. The avocet, a wading bird extinct as a breeder in Britain since 1842, has more than doubled in numbers along the tidal Thames over the past 30 years. Recovery resulted from gradual improvements in sewage treatment, pollution regulations since the 1990s, and oversight by the Environment Agency from 1996. Recent data show higher dissolved oxygen and lower levels of copper and zinc. The Thames Tideway Tunnel, operational since February 2025, has diverted over 20 million metric tons of sewage. Challenges remain, including rising nitrates, some fish declines and warming waters averaging 0.13°C per year from 2007 to 2024.
