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Fightback starts against invasive species that threaten British plants and animals

 
American Signal Crayfish

Native crayfish have suffered from the invasion of American signal crayfish. Photograph: Adrian Sherratt/Alamy

 

Powered by Guardian.co.ukThis article titled “Fightback starts against invasive species that threaten British plants and animals” was written by Conal Urquhart and Robin McKie, for The Observer on Saturday 7th September 2013 10.49 UTC

The pillwort fern is one of Britain’s most unusual – and striking – native water plants. Its tiny fronds unfurl to create lush green underwater meadows in lakes and ponds.

However, the pillwort is under threat, a victim of polluted waters and invasive species that are changing the watery habitats of Britain.

The fern is not alone. The tadpole shrimp is another rare species that finds its existence similarly threatened. Considered to be a living fossil, the shrimp – known as Triops cancriformis – has not changed in appearance since the Triassic period, 220 million years ago. Today its numbers have reached a perilously low level, and the arrival of invasive shrimps could make it rarer still.

Then there is the Southern Damselfly, which once thrived across rivers in Cornwall, Somerset and much of south-west England but which is now confined to two pockets, one in the New Forest and the other in the Preseli mountains, Pembrokeshire, a victim of the rise in water abstraction for new towns and factories, which is lowering water tables while draining land for agricultural use.

These species are just a small selection of the birds, crayfish, mammals, eels, water voles and other forms of life that are now hovering perilously close to extinction in Britain and which could now be wiped out by a chance act of pollution, a flood or a year or two of bad weather, say experts.

As a result, conservationists will this week announce the launch of the Freshwater Habitats Trust, which will focus on improving the quality of water in ponds and streams. “Research over the past 20 years has shown that, surprisingly, a wider variety of plants and animals live in the smallest waters – ponds, headwaters, streams, even man-made ditches – than in bigger lakes and rivers,” said a spokesman for the trust, which will aim to protect these smaller bodies of water.

However, water quality is only one part of the crisis. Invasive species, such as mink, signal crayfish and plants and weeds are having a devastating effect on some parts of the environment. The British water vole population has fallen by a fifth, partly because of the American mink, which escaped from fur farms and spread throughout the country.

Terrapins can now be found in many lakes and waterways after being abandoned by humans. They became popular among children when the Teenage Mutant Ninja Turtles became a television hit in the 1980s, but parents did not realise they outgrow their aquariums and outlast most childhoods, living for up to 60 years.

More than 150 terrapins were found in the ponds in Hampstead, north London, and in one pond in the former Cat Hill campus of Middlesex university an estimated 50 terrapins in a range of sizes could be seen last week. Ecologists believe that such numbers would have a major impact on fish, frog and newt numbers. All of the terrapins are believed to have been abandoned, as there has been no reported occurrence of terrapins reproducing in the wild in the UK.

In many rivers and lakes, American signal crayfish have wiped out native British white clawed crayfish by eating their eggs and passing on crayfish plague, which they carry but do not suffer from themselves.

Trevor Reynolds of the Environment Agency said that education was one of the most effective tools to combat the spread of invasive species, but the agency was running several eradication programmes countering invasive species, such as water primrose and topmouth gudgeon. “We have identified 22 sites where water primrose is present and 25 lakes which have topmouth gudgeon. Both could cause a great deal of damage and, while it is an expensive process, the future damage make [the programmes] necessary,” he said.

The campaigns against water primrose and topmouth gudgeon are possible because their spread has been caught early.

Matthew Frith, a director of the London Wildlife Trust, said that invasive species were not always a problem. “In London, we have a huge proportion of non-native species. ‘Invasive’ suggests they are a problem, but that is not always the case. There is a lot of alarmism about invasive species. In a highly disturbed and amended landscape such as here, it’s less of an issue,” he said.

“We are trying to work out which ones to focus on. There are some that are too entrenched, such as the zebra mussel and arguably the ring-necked parakeet. We can’t eradicate them but we can manage them. There are others that are not too entrenched. If we do not do it now, it will be too expensive in the future. There is a view that invasive crayfish could be dealt with, with a concerted effort.”

Frith points out that some invasive or non-native species have become a part of our landscape. “Some of the best examples are the horse chestnut tree and the London plane tree. Opinions are divided on the sycamore, but it has been around for 500 years, ” he said.

 

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