Bladderwort and bog bean might sound like something out of Harry Potter - but in reality they are having a major impact on Kent.

Because the need to protect the rare plants - along with other wildlife at a popular beauty spot - has put the brakes on huge developments across the county, driving up house prices and leaving prominent high street buildings sitting derelict for years.

You've probably heard about the Stodmarsh Nature Reserve and the concerns over water quality there. But perhaps you've also wondered why it matters to you?

The answer is simple. Because of the issues at the wildlife haven, near Canterbury, plans for tens of thousands of much-needed new homes have stalled.

Here, we try to answer the key questions about Stodmarsh and what is being done to solve a problem which has massive implications for Kent.

This includes whether new homes will be built near you - with one council warning a knock-on effect could be "uncontrolled development" in some areas.

When did the issues at Stodmarsh first arise?

In October 2020, housebuilders were hit by an environmental bombshell.

Government advisers at Natural England called for planned construction across swathes of east Kent to stop.

This included 4,000 new homes at Mountfield Park, in southern Canterbury, and the 725-home 'Large Burton' estate in Ashford.

The major redevelopment of the empty Debenhams and Nasons department stores in Canterbury was also abruptly brought to a halt, leaving these huge city centre buildings empty.

What had been found at Stodmarsh?

Experts discovered high levels of nitrogen and phosphorous in the water. This causes excessive algae growth, which had started to harm the ecology at the site.

The pollution had been caused by waste water entering Stodmarsh's lakes, which are fed by the River Stour.

As a result, Natural England said new developments must not "add the burden of nutrients such as phosphorus and nitrogen".

In basic terms, for every new house built, there is at least one new toilet being flushed on a regular basis.

Natural England put the onus on councils and developers to find a way of stopping that extra waste water ending up at Stodmarsh.

What makes Stodmarsh so special?

Stodmarsh is made up of a series of wetlands and lakes that are internationally recognised for the habitats and the wildlife they support.

This includes water voles, two rare British birds (cetti’s warbler and bearded tit), and swathes of reedbeds and grassland used by breeding and wintering bird populations.

It is also home to some scarce wetland plants - like the greater bladderwort and bog bean mentioned above.

What has been the impact on plans for new homes?

As a result of Natural England’s advice, before gaining planning permission developers now need to show their schemes can achieve "nutrient neutrality" and therefore not add to the problem.

The issue has mainly impacted the Canterbury district and Ashford borough.

But it has also affected planning decisions for Dover District Council, Maidstone Borough Council and Folkestone & Hythe District Council as they also partly fall within the Stodmarsh "catchment area".

What are councils doing to tackle the problem?

For local authorities like Canterbury City Council, with a draft Local Plan for 17,000 new homes to be built by 2040, this is a pressing issue.

Council spokesman Leo Whitlock told KentOnline: "We are looking at whether the creation of wetlands across the catchment is a way of reducing the high nutrient levels in the Stour river system.

“As part of our work on the Local Plan, experts are looking at how much wetland would be needed and where they would be best situated.

“In the meantime, we have granted planning permission for some of our strategic or large-scale schemes on the basis they will build their own on-site treatment works or create wetlands or reed beds to clean water before it makes its way into the system."

But building an on-site treatment works is far from cheap.

According to a report from the city council's head of planning, Simon Thomas, the cost is "very roughly estimated to be in the region of around £1,500 per dwelling".

This approach has been agreed for the enormous 10,000-home Otterpool "garden town" near Folkestone, the reports says.

The wetland solution has been seen in action in Ashford, where work on the previously blocked Large Burton housing estate has been able to start.

The developers are creating an “extremely complex” off-site wetland which they admit has been “a difficult issue to deal with”.

So does this solve the problem?

Not quite. Mr Whitlock admits it is "not always practical or efficient" to install local waste water treatment facilities on small or urban sites.

This is a particular problem for the Nasons and Debenhams developments in Canterbury city centre, which have permission for a total of 135 flats as well as a mix of shops and cafes.

Karl Elliott, of Clague Architects, which is involved in both projects, previously said: “We have been hearing of a multi-layered solution of ‘off-set’ land to create wetlands.

"But it will mean funding from developers, who will have to put their hands deeper into their pockets.

“It goes back to one prediction that it could be years before it’s sorted.”

This week, Alex Giacchetti from Setha Group, the team behind the Nasons redevelopment, told KentOnline they are continuing to work closely with the council and Natural England to find a "sensible solution".

"Our city centre location has been particularly difficult to find solutions for, as are all city centre locations, but we remain hopeful that we can get across the line and ultimately provide the high street with the positive investment and rejuvenation needed," he added.

KentOnline did not receive a response regarding the Debenhams development.

Mr Whitlock said: "The council is working to find a solution that can be shared by multiple small developments.”

Is the government helping at all?

Mr Whitlock says the councils have been lobbying the government with local MPs to "help us break the impasse" and has "asked them to recognise that housebuilding and job creation in east Kent is being stifled".

In response, the government awarded £100,000 to Kent County Council in April to coordinate the work between the councils affected.

“We all want to protect Stodmarsh and the whole Stour river system and ensure the wildlife and biodiversity flourishes," Mr Whitlock said.

“We also want to build much-needed homes across the district, create jobs and unlock the redevelopment of a number of important and iconic sites in Canterbury city centre which are key to the local economy as we rebuild after the ravages of the pandemic.

“So we have been working incredibly hard in the background with the councils affected, Natural England and Southern Water to see if we can find answers to this complex problem.

“We are all in this together, so we have been pulling together a strategic framework."

The Department for Levelling Up, Housing and Communities did not respond to requests for comment.

What about Southern Water?

The councils are pushing Southern Water to bring forward an upgrade in Canterbury’s waste water treatment works - currently not planned until the next investment period of 2025-2030.

In a document published online, Southern Water says it is "not feasible" for it to increase the nitrogen or phosphorus removal rate "beyond consented levels" at the treatment works.

The firm says "significant investment" would be needed, financed through income collected from customer charges, which would have to be increased - and this would require approval from Ofwat.

Council officials are also looking at ways of "tackling the run-off from farms which also adds nitrogen and phosphorus into the system".

Why should we worry about housebuilding being stalled?

Undoubtedly, many people will welcome the brakes being slammed on major housing developments.

But, as KentOnline has previously reported, the lack of new supply is having a major impact on house prices - and the cost of renting.

Since March 2020, the average cost of buying a house in Ashford has rocketed by 22% (£63,000), with similar rises seen across east Kent.

Estate agents say prices have been pushed up by a shortage of supply amid huge demand for houses.

Meanwhile, analysis by KentOnline last month revealed that in half of the county's towns, there were no houses available to rent for less than £1,000 per month.

Some residents told us they are opting to move as far as Wales to find somewhere more affordable.

Meanwhile, despite the issues at Stodmarsh, the government is not easing up on its housebuilding target for councils.

Several Kent councils were sanctioned earlier this year after hitting less than 75% of their targets.

As a result, councillors and officers must now make decisions on planning applications in line with the “presumption in favour of sustainable development”.

Mr Whitlock said: “The city council has called on ministers to make allowances for the effect the issues at Stodmarsh is having on its granting of planning permission when deciding whether to penalise us for not hitting our housing delivery target - an action that could lead to uncontrolled development in areas not affected by the Stodmarsh issue."

So, even if you don't live within the Stodmarsh catchment area, until the issue is resolved, it could increase the chances of a development being built near you.

Is Natural England going to change its advice?

It appears not.

This week, James Seymour, Natural England's area manager for Kent and Sussex, told KentOnline: “Nutrient neutrality is an approach to tackling two of the biggest challenges of our time - building the homes the country needs while also protecting our most vulnerable nature sites.

“Development proposals affecting sites legally protected for their conservation value, such as Stodmarsh, should not add to the burden of nutrients such as phosphorus and nitrogen entering the catchment.

“Local authorities are developing a catchment-wide strategy to address the potential impacts of development within the River Stour catchment, and Natural England continues to work closely with them in our advisory role.”