How wetlands reduce pollution in our waterways and urban areas - Earthwatch Europe

How wetlands reduce pollution in our waterways and urban areas

Wetlands are wonderfully wild places where wildlife of all kinds thrives. They are also vital natural resources that benefit the environment in many ways, including providing clean water, flood prevention and water storage. In this blog, we explain how wetlands reduce pollution in our waterways and urban areas.

What is a wetland?

Photo credit: Helen Burton

Wetlands are habitats that are defined by the presence of water. The water may be there permanently, frequently or seasonally. They can have fresh or salt water, adding to the complexity of the conditions.

The water in the area influences most of the habitat’s biological, physical, and chemical characteristics.

Wetlands have hydrophytic (water loving) plants that have evolved to survive in waterlogged soil with low oxygen levels.

These wetland plants have adapted to the varying water conditions at these sites such as the depth of the water or flooding frequency. This means every wetland is a unique ecosystem.

The soils are also a key feature of wetlands. They are constantly or repeatedly waterlogged or flooded for lengthy periods of time during the growing season.

The soil properties are gradually changed by the presence of water and low oxygen. These soils may be dark in colour with orange rust patches, contain undecayed plant matter, and may even smell of rotten eggs!

Wetlands are often transitional areas between upland and aquatic ecosystems or in coastal tidal zones. They may be on floodplains too in areas where rivers have moved over time occurring as part of features like oxbow lakes.

Some can be found across the landscape in depressions that collect water or at sites where groundwater comes to the surface.

Wetlands are places of rich biodiversity! Many species of wildlife depend on wetlands whilst others visit for feeding, breeding or rest.

Coastal and estuarine wetlands can support huge numbers of migratory birds and spawning fish.

Rivers, streams, and large lakes are typically not classified as wetlands.

Photo credit: Bittern, Helen Burton

The threat from water pollution

Water pollution is a huge challenge for fresh water in the UK, impacting our rivers, streams, and lakes.

In September 2024, over 4,500 people measured the water quality of their local rivers, lakes and streams as part of the Great UK WaterBlitz. The results showed that 61% of freshwater sites surveyed had poor ecological health.

Agriculture, sewage, and wastewater are causing unnaturally high levels of nutrients to enter our waterways. This results in nutrient pollution from phosphates and nitrates.

Plenty of other pollutants such as medication, tyre particles, microplastics and other toxic chemicals are also polluting our waters. All of this poses serious threats to people and wildlife.

But wetlands have superpowers that can help us in the fight against water pollution.

How wetlands reduce pollution

Photo credit: Helen Burton

Wetlands act like ‘nature’s kidneys’, removing both sediment and pollutants from water. They do this in several ways.

Wetlands slow down the flow of water. This allows suspended sediment in the water to be deposited or become trapped in plant roots.

The slower moving water enables bacteria to clean the water. Bacteria can convert toxic chemicals into less harmful forms. For example, ammonia is turned into nitrate.

Contaminants can also be trapped and stored. Many harmful contaminants bind to sediments. As these sediments settle, the pollutants become bound into the soil, locking them away from contact with plants and wildlife.

Plants growing in wetlands, along with soil organisms, absorb nutrients. This process helps remove nutrients from sewage and agricultural pollution.

The difference wetlands can make

Photo credit: Bearded reedling, Helen Burton

Wetlands can make an enormous impact! A trial of a new wetland site showed phosphorus decreased by 27.5%, with ammonia and emerging contaminants, such as medications, reduced by over 60%.

Over 90% of microplastics and antimicrobial resistance genes were also removed.

Another study, in an agricultural area, found that constructed wetlands can remove more than half of the nitrate discharging from dairy farm pastures.

At the landscape scale, wetlands within a watershed area are particularly effective at reducing nitrate levels in rivers and streams.

When stream flows are high, wetlands are five times more efficient at reducing nitrate than the best land-based conservation methods.

How wetlands reduce pollution in towns and cities

Photo credit: Helen Burton

With over 80% of us living in cities, it’s more important than ever that we make our urban areas clean, healthy places to live. Nature-based solutions such as wetlands have a vital role to play in achieving this.

Even small urban wetlands can have a significant impact on water quality. Monitoring of urban wetland sites in Enfield showed that ammonia was reduced by up to 69%. Nitrate and phosphate decreased by over 65% and the amount of faecal bacteria dropped by 78%.

Increasingly, wetlands are being used as natural alternatives to traditional wastewater treatment plants.

They are much cheaper than conventional facilities while providing extra benefits, including restoring nature for wildlife and creating spaces for recreation.

Sustainable Drainage Systems (SuDS) are often used in urban areas to manage flooding. SuDS options include adding ponds and wetlands.

An extra benefit of SuDS is that they also help to reduce pollution by trapping sediment and pollutants before they reach our waterways.

How you can help

Photo credit: Water rail, Helen Burton

Our rivers and freshwater habitats are at crisis point and we need urgent action. Sign up to the Great UK WaterBlitz to join the fight for healthy freshwater in April!

Help us build a national picture of the state of water quality across the UK. With this data we can call for more solutions to be implemented like creating new wetlands to reduce water pollution.

We’re inviting everyone to go out and test the quality of their local river, stream or lake during 25-28 April. Register your interest in taking part to get early access to sign up.

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