Our directory of things of interest

Back from the dead

Back from the dead
16 Jan
Declared biologically dead in 1950s, the Thames is now home to hundreds of species of fish, seals, porpoises and more

According to a ten-year marine mammal survey by the Zoological Society of London, there have been more than 1,000 harbour seal sightings along the river Thames over the past decade, along with dozens of harbour porpoise sightings and even the occasional whale. ‘People look at the Thames and see murky water,’ says Sofia Castello y Tickell, co-author of the study, ‘but in fact, it is full of life ranging from invertebrates to fish and top predators such as seals.’

Harbour seals have been seen at Hampton Court, porpoises and dolphins at Teddington Lock and whales as far as Gravesend

The tidal Thames had been used as the London’s drainage system for centuries before it was declared biologically dead by the Natural History Museum in 1957. The waters around the most developed areas of the city had become anaerobic – devoid of oxygen and unable to sustain life. Following the introduction of tough legislation in the 1990s, the ‘big stink’ began to make a biological comeback. Most harmful effluents are now prevented from entering the Thames and its tributaries, while sewage is treated and exported elsewhere. Given this chance, 400 invertebrates and 125 species of fish, have returned to the grey-green waters. ‘Marine mammals are most likely following their food,’ says Joanne Barker, marine biologist at the ZSL and co-author of the study. ‘Harbour seals have been seen at Hampton Court, porpoises and dolphins at Teddington Lock and whales as far as Gravesend.’ Canary Wharf is the best place to see marine species as more sightings were reported there than anywhere else along the Thames estuary.

While the water quality has improved, harmful pollutants are still adrift in the form of plastics. A study by Royal Holloway found 70 per cent of flounder had plastic in their guts. Plastics are thought to cause the bioaccumulation of toxins in marine species. ‘Although much cleaner than in the 1950’s,’ says Barker, ‘the Thames still has a number of problems and has a long way to go before I would describe it as being clean.’

This article was published in the January 2016 edition of Geographical magazine.

Related items

Geographical Week

Get the best of Geographical delivered straight to your inbox every Friday.

Subscribe Today

Adventure Canada


Aberystwyth University University of Greenwich The University of Winchester




Travel the Unknown


Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • National Clean Air Day
    For National Clean Air Day, Geographical brings together stories about air pollution and the kind of solutions needed to tackle it ...
    The Air That We Breathe
    Cities the world over are struggling to improve air quality as scandals surrounding diesel car emissions come to light and the huge health costs of po...
    Diabetes: The World at Risk
    Diabetes is often thought of as a ‘western’ problem, one linked to the developed world’s overindulgence in fatty foods and chronic lack of physi...
    The Nuclear Power Struggle
    The UK appears to be embracing nuclear, a huge U-turn on government policy from just two years ago. Yet this seems to be going against the grain globa...
    The true cost of meat
    As one of the world’s biggest methane emitters, the meat industry has a lot more to concern itself with than merely dietary issues ...


NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in PLACES...


Public transport in India could be on the verge of…


To retrace the route of the fur voyageurs on the waterways…


IPCC Cities and Climate Change Conference: Alberta host dresses non-renewable…


Increased carbon dioxide is affecting freshwater ecosystems


The latest laser scanning technology reveals new insights into the…


Deforestation is having an unexpected effect in the Amazon: fewer…


The iconic Douglas fir tree, familiar to fans of the…


Rocky Mountain forests are not regenerating after wildfires


Cape Town is edging closer to ‘Day Zero’, the long-feared…


Ongoing restoration projects are breathing new life into Florida’s Everglades


Despite protests, an experimental pedestrianisation system is proving to be…


National Archives map historian, Rose Mitchell, highlights some of the…


An expedition into the Jordanian desert is helping teachers and…


Trivia fans take note, Mount Hope in the British Antarctic…


An enormous hydropower development in Ethiopia is expected to put…


From nuclear warnings to whether your favourite band will ‘make…


New maps of global reptile distribution reveal significant gaps in…


Indigenous conservation schemes in Peru can be more effective than…


How are the EU member nations faring in the fight…


Violence against women violates human rights, and the lack of…