In 1957, the Thames was declared as “biologically dead” due to the extreme levels of pollution it suffered from - but over 60 years of environmental and conservation work has seen life return to its waters.
This is everything you need to know.
What did the report find?
According to the ZSL, the report found that the “overall picture was bright for nature, with evidence of an increase in a range of bird species, marine mammals and natural habitats such as carbon-capturing saltmarsh”.
Surprising species which now live in the Thames include “seahorses, eels, seals and even sharks”.
The Tidal Thames supports over 115 species of fish, 92 species of bird and has almost 600 hectares of saltmarsh which is crucial for the habitat of a range of wildlife.
While the report found some positives, it also “paints a worrying picture” as, alongside rising sea-levels, climate change has increased the temperature of the water by 0.2C per year, on average.
ZSL Conservation Programme lead for wetland ecosystem recovery, Alison Debney said: “Estuaries are one of our neglected and threatened ecosystems. They provide us with clean water, protection from flooding, and are an important nursery for fish and other wildlife.
“The Thames estuary and it’s associated ‘blue carbon’ habitats are critically important in our fight to mitigate climate change and build a strong and resilient future for nature and people.
“This report has enabled us to really look at how far the Thames has come on its journey to recovery since it was declared biologically dead, and in some cases, set baselines to build from in the future.”
What kind of sharks are in the Thames?
The ZSL found that “tope, starry smooth hound and spurdog” sharks are now living in the Thames.
A tope shark (scientific name: galeorhinus galeus) can grow up to six feet long and can weigh up to 48kg. You can identify a tope shark by its grey upper body, white belly, two dorsal fins and a distinctive notched tail, according to The Wildlife Trusts.
These sharks feed on a variety of fish as well as crustaceans and even cephalopods if the opportunity presents itself.
Tagging studies have shown that tope sharks tagged in the UK have later been found as far away as the Canary Islands.
The tope shark is listed as vulnerable by the International Union for Conservation of Nature red list, and is classified as a “priority species” under the UK Post-2010 Biodiversity Framework.
The starry smooth hound (scientific name: mustelus asterias) is a small species of shark which can grow up to four and a half feet, with a maximum weight of 4.8kg. The starry smooth-hound is identified by the scattered white dots around its top, fin and tail.
This species of shark feed primarily on the likes of crabs, lobsters and small, bony fish.
Finally, the spurdog shark (scientific name: squalus acanthias) is a slender shark which can grow up to three feet long, with an average lifespan of up to 70 years.
The spurdog shark gets its name from the spines found in front of its dorsal fin. It uses these spines to defend itself by circling into a bow and then striking at a predator.
It is one of the few venomous fish found in UK waters, as the spines secret a venom which can cause symptoms like swelling and discomfort in humans.
Other identifiable features of the spurdog shark is its pointed snout, big eyes, grey/brown colouring and rows of white spots down its sides.