New Zealand tourism operators are being warned the 'boom' years are over amid slowing visitor numbers.

Some international travellers are being put off by economic uncertainty and their own potential impact on the environment.

It's been a golden run for New Zealand tourism, worth $39 billion alone last year.

Now, global uncertainty is discouraging travellers in the Northern Hemisphere, who are taking holidays closer to home. 

"We're seeing visitor numbers level off after rapid growth in recent years. Other countries are competing intensely for visitors to their countries," Tourism Report Panel chairman, David Smol, told Newshub.

A report for Tourism New Zealand has recommended operators work to attract high-value visitors.

Yet with many regions struggling to cope with the recent tourist boom, slower growth may not be a bad thing.

"I think it's time for a breather. We've had huge growth over the last few years and it's time for us to catch up," says Sophie Barker from the Otago Peninsula Trust.

"We've got some challenges around sustainability of the visitor industry."

"[We need to be] making sure that when people come here, they see a country and a sector that is taking the environment very, very seriously, [to see] that we're minimising waste, we're minimising emissions," says Smol.

Tourism New Zealand will also lead new research into whether concerns over climate change and carbon footprints could cause travellers to avoid New Zealand.

"We understand what our visitor's expectations are, and how that may impact their decisions when they're purchasing holidays," says Minister of Tourism Kelvin Davis.

The long-running tourism marketing campaign, '100 percent Pure New Zealand', will continue - the extra emphasis on the warm welcome New Zealand gives to its visitors.