The zombie river? The Thames in London, once biologically dead, has come to life again: NPR

Tower Bridge over the Thames and in the distance the central central business district Canary Wharf is depicted as the sun sets in London.

Justin Tallis / AFP via Getty Images

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Justin Tallis / AFP via Getty Images

Tower Bridge over the Thames and in the distance the central central business district Canary Wharf is depicted as the sun sets in London.

Justin Tallis / AFP via Getty Images

In 1858, sewage clogging the Thames in London caused a “great stench”. A century later, parts of the famous waterway were declared biologically dead.

But the latest report on the “Thames” sounds a surprisingly optimistic tone.

The river today is “home to a myriad of wildlife as diverse as London itself,” writes Andrew Terry, director of conservation and policy at the Zoological Society of London, in a statement to the report published Wednesday. Terry points to “reductions in pressure and improvements in key species and habitats.”

Among these species are two types of seals. Before the early 2000s, little was known about their whereabouts, but now “[both] the harbor seal and the gray seal can be seen in the Thames, “the report notes, from the river’s tidal boundary west of London, through the center of the city and across its outer estuary.

Another success story pointed out in the report is the avocado, a migratory bird that became extinct as a breeding species in Britain in 1842 due to habitat loss. It began to make a comeback after World War II, and over the past three decades, its population seen in the Thames has more than doubled, according to the report.

There are promising trends, but still plenty of caution

The report highlights several promising trends. But it also warns that there is still work to be done in other areas, and warns of the negative impact of climate change on the river, which is an important source of water for the city.

“Concentrations of dissolved oxygen, which are crucial for the survival of the fish, show long-term increases,” it says. “Additionally, phosphorus concentrations have been reduced in both the long and short term, demonstrating the effectiveness of improved wastewater treatment work to reduce the harmful levels of nutrients entering water bodies.”

The short- and long-term prospects for birds and marine mammals on the river are improving, according to the report. However, it says that the situation for fish is getting a little worse in the long run. Although it may be due to changes in sampling methods, it may also “be an indication of pressure on fish stocks either in the Tidal Thames or further afield,” the report says.

The report also warns that “a long-term increase in nitrate concentrations” could also threaten water quality.

“In addition, the effects of climate change are clearly affecting Tidal Thames, as both water temperatures and sea levels continue to rise above historical baselines,” it states. “This will undoubtedly affect the wildlife of the estuary, which will lead to changes in life history patterns and species areas.”

The report says that the expansion of wastewater treatment plants, which began in 1960, and restrictions on industrial discharges have helped purify the Thames to some extent.

“But because London’s sewer system was largely built in the 19th century, when London’s population was less than a quarter of what it is today, storm events cause excess sewage to overflow into the Tide Thames, posing a major threat to water quality. “adds it. .

A ‘super sewer’ comes to the Thames to help the estuary

There is a possible solution on the horizon. London is currently building a “super sewer” project called the Thames Tideway Tunnel and is due to be completed in 2025.

“Once operational, it will collect and store most of the millions of tons of raw wastewater currently flowing into the estuary,” the report said.

Despite improvements to the river’s water quality, a research paper published last year indicated high levels of microplastics in samples of the Thames water column taken in 2017.

Experiments have shown that such microplastics can have harmful effects on aquatic organisms, as well as turtles and birds, according to national geography. Among other things, they can block the digestive tract – with some animals dying of hunger when their stomachs are filled with plastic.

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