So close and yet so far: Toilet paper left beside a toilet near Tinline Bay in the Abel Tasman National Park.

DOC is pushing out a new slogan after high levels of tourism strains the Abel Tasman: please, "poo in a loo".

The common-sense campaign has been made necessary as once again Abel Tasman National Park has been given the litter-box treatment, with human waste and used toilet paper left in the open by the walking tracks.

Not only will DOC be reminding visitors to go to the toilet when there is one available by way of new signage, but they will also be following up with visitors in a survey asking if they saw the signs, how well they understood them, and if the signs "influenced them to use a toilet", DOC said in a statement.

The Abel Tasman was chosen for this pilot project because of its high visitor numbers, about 300,000 a year, and because people "toileting in the bush is the main visitor behavioural problem in the park".

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DOC Motueka operations manager Mark Townsend said that "pooing outdoors is a growing problem on some popular tracks".

"It's not feasible or desirable to try to solve this by putting a toilet on every corner in our great outdoors – influencing behaviour is key to solving this problem."

Marion van Dijk Visitors are causing mess in the Abel Tasman and other popular walking tracks by pooing in the open - not in toilets.

Instead of new toilets, DOC is trialling new signs telling people the distance between toilets, including last-chance-to-go signs explaining the short distance to the nearest loo and the "considerably longer walking time" to the next available toilet.

"People come to Abel Tasman National Park to enjoy its beautiful natural environment and we ask visitors to respect and look after the environment by using the toilets provided and not going in the bush," Townsend said.

"There is signage already in the park and at its entrances about toilets but the new signs are an additional reminder to use the nearest toilet while you can."

Martin de Ruyter Toilets are available at most huts, camping sites and bays where water taxis pick up and drop off passengers.

The longest distance between toilets is the three hour walk between Torrent Bay and Bark Bay.

Townsend said most Abel Tasman visitors were responsible, but those who left behind human waste were causing not just an unsightly mess but a dangerous one for visitors and DOC rangers.

"Leaving human waste near water risks spread of diseases like giardia into waterways. Weka are also picking up and spreading human poo which increases the risk of it being a health hazard.

"Most people don't like seeing human waste, toilet paper and other sanitary waste in the bush, and our rangers remove it when they see it. Cleaning up biohazards is not straightforward work; strict procedures need to be followed to protect rangers' health."

Before the campaign, DOC's audit of the track found human waste, toilet paper, wipes, incontinence pads, nappies, and "other sanitary products".

DOC will be monitoring human waste and sanitary items at "bush toileting hotspots" throughout the trial.