They sit in your garden pond, adding a bit of exotic charm – but they are deadly. And five popular aquatic plants will no longer be available from nurseries, as the threat they pose to Britain’s environment is just too great.
The five, all non-native species – meaning they come from other parts of the world – are water primrose, floating pennywort, parrot's feather, water fern, and Australian swamp stonecrop. All have the potential to cause immense damage if they escape into the wider aquatic environment here, choking watercourses and crowding out and killing other wildlife. And yesterday they were banned from sale.
From next year, the Environment Minister Richard Benyon announced today, garden centres, nurseries and other horticultural retailers will have to stop selling them or face a fine of up to £5,000 and possibly up to six months in prison.
It is the first time that non-native plants have been banned from sale in Britain, and is a clear sign of the tightening-up of the precautionary regime against invasives, not least in the aftermath of last year’s arrival from continental Europe of ash dieback disease, which partly came in on nursery plants, and is likely to kill all the ash trees in the UK, whatever the Government does.
It is also part of a growing recognition that invasive species of all kinds, and the damage they cause to other ecosystems, now represent one of the four major threats to wildlife the world over, along with habitat destruction, pollution and overhunting.
Britain has a huge number of non-natives species – if we use the definition of creatures and plants which have been introduced by humans since the end of the Ice Age, the total is more than 2,700 – but it is a smaller yet still significant number, introduced more recently by the processes of globalisation, which are causing problems.
Three of the five banned plants are on the “top ten wanted list” of the most damaging alien species produced by the Environment Agency eighteen months ago: water primrose and floating pennywort are numbers two and three on the list, while parrot’s feather is number ten.
In the past they have been sold and planted in garden ponds, but have escaped into the wild taking over from native species and damaging some of our most sensitive habitats. The plants form dense mats in water, depleting oxygen and light availability, causing declines in the numbers of fish and other aquatic species; they also reduce access to waterways for boating and angling and increase flood risk which, taken together, can cost millions of pounds per year.
Floating pennywort, which can grow up to eight inches a day, costs the British economy £23.5 million per year, the Department for Environment, Food and Rural Affairs (Defra) said today, while invasive non-native species as a whole can mean a devastating outlay to the economy, costing £1.7 billion to control.
It is not just plants: many forms of wildlife, originating elsewhere, are now damaging the environment in Britain, from the harlequin ladybird from Asia, wiping out British ladybirds, to the “killer shrimp” from Eastern Europe now threatening fish populations or the horse chestnut leaf-miner moth from the Balkans wreaking havoc with our conker trees. Deer such as the muntjac from China are threatening Britain’s nightingales, as they destroy the woodland undergrowth in which the birds breed.
Conservationists warmly welcomed the plant sale ban today. “Headlines about ash dieback were just the tip of the iceberg,” said Carrie Hume, Head of Conservation Policy at the Wildfowl & Wetlands Trust. “The truth is that British nature is under relentless attack from a whole host of invasive plants and pathogens that are freely imported and cultivated for sale.
“Thankfully, some of the most destructive non-native plants will no longer be on sale in our garden centres. This is the right move. The environmental and economic cost of dealing with this problem is already huge and dealing with it now is a great saving for the future.”
Matt Shardlow, Chief Executive of Buglife, the Invertebrate Conservation Trust, said the ban was “fantastic news”. He said: “It is long overdue. It is part of a process of recognising that foreign trade in wild plants has sever implications for biodiversity.”
Britain is one of the few countries actually to have a formal non-native species strategy, which maintained by the GB non-native species secretariat, based in York. The strategy, in place since 2008, seeks to prevent new problems by a system of risk assessment of potentially dangerous species; it will be reviewed by the Government later this year.
In the meantime, the European Union is expected soon to bring forward proposals for the first-ever EU non-native species legislation.