Anti-graffiti machine gets rid of invasive alien species

A WWT worker uses the hot-water weedkiller on its Martin Mere reserve. Photo: WWT.
A WWT worker uses the hot-water weedkiller on its Martin Mere reserve. Photo: WWT.
Martin Mere WWT has found a novel use for a machine that usually cleans chewing gum and graffiti from towns and streets.

The Lancashire wetland centre is using the Cardley-Wave machine to eradicate aquatic non-native weeds from its wetlands, to protect native British wildlife.

The machine sprays a targeted jet of hot water – a bit like a carpet cleaner – which can also be used to kill individual weeds. Unlike chemical-based weedkillers, there is no danger of other wetland plants and animals like irises, dragonflies or frogs being affected by any chemical run-off into the wetland.

Invasive non-native species are estimated to cost the British economy at least £1.7bn per year. For example a species like Creeping Water Primrose would usually compete for space across the huge Pantanal wetland in South America, but when released into a small English stream it can easily overrun native plants and pond life and starve them of oxygen, light and space.

The machine is widely used by local authorities on the Continent for street cleaning, including clearing weeds from pavements, which sparked WWT’s interest. It’s the first time the machine has been used for environmentally friendly weeding at a nature reserve in England. Meanwhile one of WWT’s sister wetland centres at Llanelli in Carmarthenshire has become the first nature reserve to use the technique in Wales.

WWT Martin Mere Reserve Manager, Tom Clare said: “Non-native species are being introduced to and colonising new areas around the world more rapidly than ever before, due to human activities and changes in climatic regimes. These species are termed ‘invasive non-native species’ and wetlands are particularly severely affected.

“This new equipment will ensure we can control these with no ill-effects to the [habitats]. The hot-water system can be applied accurately to the weed, killing it in a way that has no negative impact on our water, environment or wildlife.”

The Cardley-Wave Mid-Series 22/8 is simply comprised of a pump and water heater. It is transported from site to site on the back of a truck or trailer which also carries a large water tank. The water heater can be set to deliver either hot water or steam via a hose that can be fitted with a range of attachments to suit the task at hand. Weeds can be soaked over a period of time to totally kill the toughest varieties but smaller weeds can be seen wilting after one treatment.

The government has a long-running campaign to help reduce the spread of invasive non-native species. The Be Plant Wise campaign encourages gardeners to Know What You Grow, Stop The Spread and Compost With Care. Meanwhile their Check Clean Dry campaign encourages water users like boaters and anglers to clean their equipment after use. In all cases, the key is to avoid transferring plant seeds and fragments between different waterbodies.