The results of the first ever State of the Thames report were released by the Zoological Society of London in November 2021 — and there's both good and bad news for London's main waterway.
ZSL — the conservation charity which runs London Zoo — brought together experts from 16 different organisations to conduct a full 'health check' on 215 miles of the Thames, looking at factors such as wildlife, ecosystems, pollution and climate change threats.
Wildlife in the Thames
First up, the good news. Since the Thames was declared 'biologically dead' in 1957, bird and marine mammal species living in and around the river have increased greatly. Seals, seahorses and eels are among the species now residing in our river, along with, surprisingly, tope, starry smooth-hound and spurdog species of shark. Natural habitats such as saltmarsh — which captures carbon and therefore helps in the fight against climate change — are also on the increase.
Conversely, the number of fish species found living in the tidal Thames has decreased since the 1990s. Further research is needed to find the cause of this.
Climate change and the Thames
It's not all good news though — like everywhere else, the Thames is vulnerable to the effects of climate change, predominantly through changes in water temperature and sea levels. The Thames is increasing in temperature at an average of 0.2°c each year, which can damage ecosystems and wildlife stocks by causing creatures to adapt their habits and ranges.
Water levels are also rising in the Thames — at Silvertown, there's been an average increase of 4.26mm per year since 1990, which contributes to the threat of flooding in London.
Sewage in the River Thames
The release of raw sewage into our waterways is under more scrutiny than ever. The majority of the capital's current sewage infrastructure was built in Victorian times, for a much smaller population, so can be overwhelmed with current volumes, causing sewage to leak into the Thames.
That said, water quality improved between 2007 and 2020, with dissolved oxygen concentrations increasing — low concentrations can kill fish, so that's good news. Additionally, phosphorous concentrations have decreased since the 1990s, showing that improvements at sewage treatment works have been successful in reducing phosphorus entering the river, which makes for cleaner, healthier water.
What is being done to protect the Thames?
As with pretty much everywhere on Earth, the Thames needs climate change to be stopped in order to guarantee its future as a living river. Water temperatures and levels must be prevented from rising any higher, and water quality must be improved.
The Environment Agency has put together the Thames Estuary 2100 Plan which sets out a long-term approach for adapting to rising sea levels for the rest of this century, in order to protect London from flooding. Natural approaches, such as increasing Thames habitats including mudflats, wetlands, tidal marshes, reedbeds and saltmarsh, are part of the plan, as well as funds to upgrade flood defences.
James Brand, Thames Estuary 2100 Advisor at the Environment Agency said:
We are pleased to support the State of the Thames Report published today. If we are going to tackle the climate emergency, nature needs to be at the heart of our solution, both in slowing the pace of future change and adapting to the changes that we are already seeing.
Additionally, it's hoped that the problem of sewage entering and polluting the waterway will be drastically reduced in the coming years. The Thames Tideway Tunnel, known as London’s new super sewer, should capture more than 95% of the raw sewage released into the Thames once it's completed in 2025.
The State of the Thames report also features the first ever indicator for plastic pollution in the Thames, allowing scientists to monitor the situation in years to come.
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. 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.
As a result of the report's findings about the impact that climate change is having on the tidal Thames, ZSL is calling on world leaders to commit to tackling biodiversity loss and climate change at COP26 — which, at the time of writing, is ongoing. You can support ZSL's conservation work by donating to the charity.
Read the full State of the Thames report.