Maximum penalties in the tens of thousands of dollars apply for using routes that are closed to contain dieback disease

A hiker in New Zealand has become the first to be charged with walking on closed tracks in the Waitakere ranges, violating a ban put in place to stop the devastating spread of a fungal disease called kauri dieback.

Potential fines of tens of thousands of dollars apply for repeatedly using the tracks, which are closed to the public to let the forest recover from a disease that kills the majority of kauri trees it infects.

The Auckland mayor, Phil Goff, said the hiker walked on the closed tracks three times in the past five months and a stern response was needed to deter others from behaviour that threatened the survival of one of the country’s most precious native trees – sacred to its Indigenous people and prized for its beauty, strength and use in boats, carvings and buildings.

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Each breach carries a separate maximum penalty of NZ$20,000 (£9,900).

Most hiking tracks in the Waitakere ranges have been closed for over a year, with the local Māori iwi, Te Kawarau ā Maki, also placing a rāhui – temporary ban – over the area.

“Those individuals who flout the rules with no regard for the damage they cause need to be held to account,” Goff said. “This prosecution reflects the seriousness of the issue and sends a clear message to anyone breaching closed tracks areas that we will take enforcement action.

“The survival of our most iconic native tree is at risk and the decisions to close the tracks are based on hard evidence about what is necessary to slow and reverse the spread of kauri dieback disease.”

Kauri dieback can be spread by as little as a pinhead of soil on the sole of a hiker’s boots or a dog’s paw, according to the ministry of primary industries.

There is as no known cure for the disease and the trees are facing “functional extinction”, the ministry says, despite a government working group set up in 2018 to tackle its spread.

In addition to the latest prosecution, which will head to the courts in January, Auckland council has issued 49 trespass notices in the past six months, and ranger numbers will be increased over the summer months to patrol the closed tracks.

In 2018 the conservation minister Eugenie Sage told the Guardian that kauri dieback was “devastating” for New Zealand’s unique flora and fauna, but said the Department of Conservation (DOC) was confident the risk of the disease spreading by human traffic was “very low” and wild pigs were in the crosshairs.