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Rogue carnivorous plant-lovers sabotage national park

Sharp-eyed plant experts tramping in the Tongariro National Park have spotted butterwort - a carnivorous plant that is classed as an invasive weed and poses a danger to native wetland species. The Department of Conservation says it's likely that someone passionate about the insect-eating specimen has deliberately introduced it.

Tongariro's senior ranger for biodiversity, Alison Beath, is asking people to keep an eye out for other incursions and to report them to DoC. They are likely to be in accessible damp areas - where the plants thrive - next to tracks or roads. The plants were spotted last month on the Taranaki Falls Track.

Two years ago another release was discovered nearby in Horopito, and seven years ago there was a case near Tairua on the Coromandel Peninsula. They are hard to get rid of - Beath says at one site 400 plants had taken hold and they popped up again after spraying. Their pretty purple flowers appear over summer. The plants have tiny, sticky hairs, which is how they catch insects. They thrive in nutrient-poor soil.

Beath says there are three reasons why anyone might be illegally planting a European invasive plant in a national park.

"Apparently carnivorous plant enthusiasts can get a bit “over-enthused” and are trying to get butterwort established. They will be bringing it into the country illegally and will be trying to establish a wild population," she says.

"Some people passionate about carnivorous plants have a bit of a weird view that New Zealand's bio-diversity needs enriching and they're releasing it because they think it would look nice out there. It is a beautiful little plant.

"Some believe that establishing it here will help it globally in terms of it being threatened elsewhere."

The third reason people may be taking their gardening trowels into the bush is more deliberate and sinister. They may be trying to establish populations in the wild so they can trade in the plants. Currently under the CITES agreement on endangered species several varieties of carnivorous plants can't be sold in New Zealand. But if a population is established in the wild, that would change.

The mentality of someone who would do this escapes conservationists. "You'd think being a plant-lover they'd be into the environment," says Beath. "I guess if they're passionate about a particular plant, maybe they don't understand or see the bigger picture."

University of Auckland ecologist, associate professor Dr Margaret Stanley, says it's not difficult to source such plants, which are readily available on internet sites such as eBay and AliExpress. "Our border can be quite leaky ... the MPI dogs are running them down but some will sneak through." The collector mentality has been responsible for several ecological disasters over the years.

"Some people passionate about carnivorous plants have a bit of a weird view that New Zealand's bio-diversity needs enriching and they're releasing it because they think it would look nice out there."

"We had problems in Auckland with coarse fish being released by someone who'd grown up coarse fishing in England and wanted his grandchildren to have the same experience ... so now they're all through our waterways," she says. "The European Alpine Newt was released purposely by someone from England." Collectors of passionfruit flowers have also been responsible for incursions.

"Perhaps we are not working with the whole of the New Zealand community - and in particular newer immigrants to New Zealand," says Stanley.

"They're used to living with a particular food or plants ... or pets. We'd be naive to think that there are not people keeping snakes and things in New Zealand."

Stanley says the trouble is those people are not looking at the level of endemic flora and fauna here - 80 to 90 percent of it is found nowhere else in the world. "Some people get a strong idea of biodiversity being a global thing," she says. But many people don't appreciate that saving a plant or animal that might be endangered overseas by bringing it to New Zealand gives it too much of a natural advantage. With no natural enemies it can grow faster and overwhelm native species.

Stanley suggests that's not understood well by people who come from places that don't have much in the way of unique species - because the message isn't sheeted home to them. But she's scratching her head over people who love a particular plant so much they are willing to endanger the environment for it.

"We need more people working as social scientists to figure out why they have this mentality."

Unitec botanist, Associate Professor Peter de Lange, had an insight into the fanaticism of some carnivorous plant fans when he encountered one in the field some years ago, who told him all about his planting activities. This new discovery makes him angry. He points out that as well as prohibiting the growth of native plants, we have no idea what type of native insects the butterwort might be getting rid of.

De Lange says over the last 15 years a range of carnivorous plants in 'wild' sites including Venus flytraps, pitcher plants and an assortment of sundews and bladderworts have been discovered. He believes a key driver seems to be their high commodity value in this country, and the possibility that if they become established they can then be traded, side-stepping the CITES rules.

However there's also the 'Johnny Appleseed' factor - "people who believe that such actions assist the conservation of these plants (which are often threatened in their country of origin), the view being that New Zealand doesn't have them, so we can handle having them established here as that will help save them globally".

Then there is the logic that saw an Auckland man release rainbow parakeets on the North Shore - because New Zealand birds were too dull. "Some people genuinely believe New Zealand needs to be more colourful," he says.

If you spot butterwort plants, DoC is asking you to contact its hotline - 0800 DOC HOT. De Lange says a great app to download is iNaturalistNZ, which is great for identifying mystery plants.