The following article focuses on the Zoological Society of London’s (ZSL) report: The State of the Thames 2021. The report expertly details the past 60 years of environmental changes along the Thames and its estuaries.
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The Thames River is a vast ecosystem negatively impacted by modifications and an increasing human population. The report sets important benchmarks and monitors trends while expressing the importance of the river to both humans and wildlife.
Background Information and the Importance of the Thames
The River Thames symbolizes the people and culture of the Great City of London. The river connects the south and north banks of London while crossing over 33 bridges, with the river offering a lens to more than 2000 years of the river Thames' human occupation. The Thames runs for 220 miles from mouth to the source and is relatively famous for being a short river.
The Thames River estuaries support millions of people and wildlife species making it one of the most productive ecosystems in the world. In particular, the tidal Thames estuary is home to 115 different species of fish and 92 species of birds.
It provides drinking water, food, recreational and wellbeing opportunities, and protection from coastal flooding. There is no denying the asset to the community the river Thames and its estuaries are. However, it has been greatly modified resulting in a threatened ecosystem.
The Current State of The River Thames Environment
In 1957, the River Thames was declared biologically dead, which implied that the river or water body would not be able to sustain any life form and wildlife. Approximately 60 years later, the river Thames has been revived through enormous hard work and government policies. It is now a natural home for numerous wildlife species, namely sharks and seahorses.
The report further highlighted various challenges the River Thames experienced such as the sea levels and water temperature rising due to climate change.
The most significant rise in water temperature is in the Upper Tidal Thames by an average of 0.19 degrees Celsius per year. An increase in water temperature is associated with significant degradation to sea life in both the short and long term.
A further result of the impact of climate change is the rise in sea level. As a precaution, the environmental agency has established the Thames Estuary 2100 plan to mitigate, monitor, and respond to potential flood risks.
Since 1911, when monitoring of the sea level rise began, all gauge sites across the tidal Thames have been significantly increasing. The plan covers an analysis of the change in the estuary, adapting defensive flood structures, and protecting and recovering impacted wildlife habitats.
In addition, the report discovered that the River Thames had an elevated amount of nitrate. While there are no short-term spikes or increases in nitrate levels, the long-term trend shows a gradual increase. This poses a threat to the water quality of the river, while the majority of the drinking water in London is sourced from the river. This is particularly due to both industry and sewage discharge.
Sewage Pollution and Mitigation on the River Thames
During the great industrial revolution, human waste and toxic runoffs from tanneries were dumped into the river. An event in 1858 called the Great Stink, which was a result of human sewage flowing into the Thames, compelled the British parliament to design and construct an effective wastewater disposal system.
During the 1960s, through the expansion of sewage treatment works and limiting water abstraction, the situation largely improved. However, as the population of London has grown over four times since the 1800s, storms can cause the sewage system to overflow into the Thames.
To address the further threat of sewage pollution in the river, the tideway tunnel is in construction with an expected completion date by 2025.
The tunnel has been designed to run from Acton (west) to Abbey Mills (east). The Zoological Society of London report elaborated how the clean-up of sewage performed on the rivers over the recent decades significantly reduced the levels of chemicals such as phosphorus.
Environmental Protection Against Microplastics
Successful protection of the environment has not been the model of the Thames River. According to a study by British scientists, the Thames River may be free of a considerable amount of toxic waste but is still the leader in the concentration of microplastics in the world compared to other urban waterways such as the Danube in Europe and the Chicago River.
The physiological and toxicological threat to the animal is considerably high due to the tiny plastic fragments which separate from large pieces of trash that could be ingested. Most of the pollutants entering the world's oceans from rivers contain plastic waste, posing a threat to wildlife. Approximately 94,000 microplastics per second flow down the River Thames.
Further research and analysis are required to determine the sources of microplastics. However, there is hope after the completion of the sewage tunnel microplastic concentration in the Thames could decrease due to the contribution sewage overflow may have.
The Current State of Nature
Reconnecting, protecting, and restoring nature through innovating modern methods of maximizing opportunities for wildlife will promote a positive future for both people and wildlife.
The habitat's importance and value to the species on the Thames are predominantly invisible. The habitat provides substantial ecosystem services such as carbon sequestration, natural flood defenses, food production, and water quality regulation.
The River Thames’s tidal states have been massively altered over the decades. Despite the alteration, the tidal still contains numerous habitats that are essential to a diverse array of species.
Being greatly modified makes the habitat susceptible to non-native invasive species. While currently there is no apparent harm to the estuaries by non-invasive species, a total of 96 species have been discovered between 1800 to 2010. This does show a great vulnerability to potential harmful species and efforts to improve the health of the Thames will only strengthen the function of the ecosystem.
The main goal over the years for the Tidal Thames was for it to be able to function ecologically, resulting in a connected and resilient habitat that enables wildlife to flourish.
Landmark State Of The Thames report launches
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Habitat Conservation and Restoration
Conserving existing habitats is the best way to cultivate ecosystem resilience. This can be achieved if the footprint and quality of the remaining natural habitats are properly maintained. The Thames covers a total land area of 15.531 ha of nature sites of scientific importance and conservation. Increasing legal protection against development pressures could assist in the protection of nature reserves.
The UK government has identified Saltmarsh habitats as a priority due to their dynamic and critical resources for many wildlife species. Saltmarshes are important habitats as they offer a barrier to mitigate the risk of flooding and offer nesting and shelter for migratory birds and other wildlife.
In the data collection period of 1888 to 1910 in the tidal Thames, there was 1039 ha of Saltmarsh. In the most recent period of exploration from 2012 to 2018, the saltmarsh area decreased over time to 590 ha. However, this area has increased in recent years due to gradual habitat protection methods.
Techniques that have been already implemented to improve saltmarsh habitats along the Thames are managing realignment. This incorporates rebuilding flood defense structures that are breached, especially along the salt marsh.
The Essex Native Oyster Restoration Initiative along with other conservation bodies have projects in place to restore native oyster habitats. It involves laying down cultch on the seabed to provide nutrients and settlements.
The Current State of Wildlife
With the estuaries being one of the most naturally productive ecosystems on the planet, they provide numerous habitats for a range of wildlife. They are also loaded with rich amounts of nutrients which is a source of food for the food chain and thus making them a support system for a wealth of biodiversity.
The Current Status of Fish Species
For the life cycle of numerous fish species, the estuarine environment of the Tidal Thames facilitates numerous benefits such as nursery habitats.
The estuary also acts as a passage for fish during migration as they move from freshwater or out to the sea. The fish also play a vital role in the estuarine food web. Their distribution, diversity and abundance in the estuary can assist in assessing the ecological resilience or status of the estuarine.
The long-term trend of fish species in the River Thames has been deteriorating while the short-term trend of the species is stable. The data on fish is very hard to record because of the challenging dynamic environment of the estuaries.
The Migration of Birds Throughout the Thames
The birds spend the entire year in the United Kingdom habitats with other bird species only spending part of the year there. The UK is an ideal winter habitat because of its mild winter temperatures compared to northern Europe.
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The intertidal mudflats and wetlands in the Tidal Thames are heavily relied upon by wildfowl and wading birds during winter migration. Critical habitat is provided by the Tidal Thames at all times of the year during a range of bird species’ stays.
On average between 1993 to 2017, the population of Walder doubled in the Tidal Thames, while there has been a decline in the wildfowl population during this period. Though the decline of wildfowl has declined nationally in the past 20 years. The primary threats to the wildfowl population are pollution to breeding and wintering grounds and loss of habitat.
The Effect on Marine Mammals
The harbor seal (Phoca vitulina) and the grey seal (Halichoerus grypus) are predominantly the two marine mammal species in the Tidal Thames. They are both heavily dependent on the food and habitat the estuary provides, with the harbor seal utilizing the estuary as a birthplace for their pups.
The shallow depths of the Tidal Thames cannot accommodate large animals such as whales. Smaller species such as minke (balaenoptera acutorostrata) occasionally visit the estuary.
Transient visitors such as harbor porpoises are found in the Thames Estuary with a study discovering that a significant presence of porpoises is found year-round in the Estuary. It was estimated that the population in 2019 of grey seals was ~3,200 and harbor seals were ~ 900. The population of both grey and harbor seals has steadily and clearly increased since the surveys began in 2003.
The Cognitive and Recreational Benefits to the Community
The understanding and learning derived from the natural world can be defined as cognitive benefits within the context of ecosystem services.
Humans obtain multiple cognitive benefits from nature which includes engineering advancement inspired by nature design, scientific discovery, and knowledge about the environment. The Tidal Thames is a vital source of cognitive benefit as it is accessible to millions of people and has a diverse environment.
On the river and by the river are two of the general categories for blue space recreation. Examples of popular by-the-river activities are cycling, running, and walking. Examples of on-the-river activities are canoeing, rowing, and kayaking.
The exact relationship between the number of leisure users and environmental quality is unknown. Thriving and healthy Tidal Thames would captivate and appeal to more people by and on the river. Only by improving the quality of the water system will the community be able to utilize and attain these benefits.
The Future Outlook
There have been numerous improvements to the water quality in the Tidal Thames and to the estuary ecosystem. This was achieved through hard work between various organizations and people, such as the Environment Agency, which was influential in pushing for greater investment in sewage treatment works to increase treatment amount, level, and quality of wastewater entering the river. The agency also assisted in constituting management structures that underpinned the continual recovery and protection of the Tidal Thames.
There are potentially new techniques that can assist in enhancing and safeguarding the Tidal Thames ecosystem. The innovative habitat restoration techniques will offer an opportunity for historically degraded habitats to be revived and returned to the Tidal Thames. The wildlife and rivers' growing appreciation suggests that the public will be in strong support of projects which assist in restoring and safeguarding the river.
References and Further Reading
ZSL (2021). The State of the Thames 2021: Environmental Trends of the Tidal Thames. McCormick, H., Cox, T., Pecorelli, J., and Debney, A.J. (Eds). ZSL, Regent’s Park, London, UK. https://www.zsl.org/sites/default/files/ZSL_TheStateoftheThamesReport_Nov2021.pdf
Cheng, A., 2021. London’s River Thames, now home to sharks, seals and sea horses, is no longer ‘biologically dead’. [Online] Washington Post. Available at: https://www.washingtonpost.com/world/2021/11/11/sharks-thames-river-london/
WION. 2021. Sharks spotted! London's River Thames no longer 'biologically dead'. [Online] Available at: https://www.wionews.com/world/sharks-spotted-londons-river-thames-no-longer-biologically-dead-428629
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