Seals, dolphins, porpoises thriving in Thames

Seal of approval: Scientists used aerial photography to count up all the seal pups.

Does nature always bounce back? The Thames, declared dead, devoid of oxygen in the 1950s, has been brought back to life by its new marine life — including sharks and the odd, visiting whale.

“The tidal reaches of the Thames constitute a badly managed open sewer,” reported The Guardian in 1959. “No oxygen is to be found in it for several miles above and below London Bridge.”

The river, which winds through the heart of one of Europe’s biggest cities, was declared biologically dead in 1957. In the years since, its churning brown waters have been written off as dirty and toxic.

So, scientists from the Zoological Society of London were astounded when, last month, they found 138 seal pups lounging on the banks of the Thames estuary.

Both harbour seals and grey seals treat the river as home. While harbour seals are born downstream, close to the sea, they often swim through the busy city and all the way to Richmond, in west London, in search of prey.

“The seals would not be able to pup here at all without a reliable food source, so this demonstrates that the Thames ecosystem is thriving,” said conservation biologist Thea Cox.

Delicious grub up for grabs includes two species of shark, short-snouted seahorses and the European eel, which is critically endangered.

The seals have competition from other Thames residents, including porpoises, dolphins and, of course, very important visitors like Benny the beluga whale.

Elsewhere, there’s more good news: across the British countryside, goldfinches and wood-pigeons can be heard twittering once again. The number and variety of birds in Britain is rising after years of decline, mostly thanks to the popularity of garden bird feeders.

Further afield, scientists recently detected that the song of blue whales has been dropping in pitch across the world. They were puzzled: was it a side-effect of the climate crisis? But no: they now believe that blue whale numbers are growing, so whales no longer need to strain their voices to be heard by their kindred.

News about the natural world is can be relentlessly awful. Earth is in the midst of its sixth mass extinction. Humans have wiped out over half of the planet’s animals since 1970. But, now, there are some rays of light in the gloom.

Does nature always heal itself in the end?

Make nature great again

Of course, say some. Look at what happened to the dinosaurs, when the sun was blocked out by dust for decades, or during an Ice Age, when the planet turned into a barren ball of ice. The Earth has seen calamity and destruction many times over its three-billion-year history, but life always finds a way to adapt and rise again.

But our era is unprecedented: we are radically changing the chemical composition of the Earth’s atmosphere. The Thames may be full of fish, but their bellies are full of micro-plastics. The Earth’s most biodiverse forest, the Amazon, is burning at this very moment. If some animals are recovering, that’s thanks to our dedicated conservation efforts. It doesn’t just happen by magic.

You Decide

  1. What could you do in your life to protect wildlife?
  2. Will humans destroy life on Earth?


  1. For a week, keep a diary of any wild animals you see.
  2. Choose an endangered species and make a chart showing how its population numbers have changed over the last fifty years.

Some People Say...

“Nature’s music is never over: her silences are pauses, not conclusions.”

Mary Webb (1881-1927), English author

What do you think?

Q & A

What do we know?
Scientists from the Zoological Society of London chartered a plane to take aerial photographs of the Thames, for the first comprehensive count of seal populations for several years. They were “thrilled” to find 138 pups on the Thames estuary, which leads out of east London towards the sea. The scientists say it is evidence that the river’s water quality is improving, thanks to improved sanitation measures.
What do we not know?
The long-term health of the river. Around 75% of flounder fish in the Thames have micro-plastics in their stomachs. We do not yet know about the future health of the fish or bigger mammals, like seals, that feed on them. Micro-plastics are also entering our food chain through fishing and bottled water.

Word Watch

Biggest cities
By population, Istanbul, Moscow and Paris are the only cities in Europe bigger than London.
Brown waters
This does not, in fact, mean that the river is dirty. The river is very tidal, with the water levels changing by eight metres every day, which drags up mud from the riverbed. This muddiness is good for diversity: it allows plankton to thrive.
Benny the beluga whale
Benny lived in the Thames for around three months from September 2018, before heading home to the Arctic Ocean.
Bird feeders
We own enough bird feeders to keep almost 200 million birds from going hungry.
Groups, usually people, related to one another.
Sixth mass extinction
The last mass extinction was the death of the dinosaurs, 66 million years ago.
Chemical composition
Greenhouse gas concentrations are rising, which is raising global temperatures.


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