A report predicts populations in many regions will drop or stagnate within three decades.
The Maxim Institute's report said populations in about 44 of the country's 67 authorities would stagnate or decline within 30 years, compared to 11 areas now. That could place them under severe financial strain as they try to pay for infrastructure.
While centres such as Auckland, Hamilton, Wellington, Nelson, Canterbury and Queenstown are set for growth, the report painted a bleak picture for most other regions.
These included Rotorua, Taupō, Gisborne, Hawke's Bay, Kaipara, Southland and the West Coast.
Maxim Institute chief executive Alex Penk said the government's regional development programmes focused solely on economic growth - but the population trends posed a big challenge on that front.
"In fact they mean that for some regions growth is not going to be the reality."
Some towns, including Kawerau and Matamata, were already working to manage decline in their areas.
"They created a wrap-around programme that relocated workers from one region to where the jobs were in the other region.
"That's the kind of response that we could actually have on the table, if we start talking about the reality that's facing us and I think that's actually a really positive opportunity for us. It isn't something we should be afraid of."
Massey University demographer Paul Spoonley, editor of the book Rebooting the Regions: Why low or zero growth needn't mean the end of prosperity, agreed decline was something that needed to be accepted, especially by politicians.
"There aren't many politicians around the country who are going to want to talk about decline.
"When you begin to talk about the demographic challenges and the economic challenges that are coming, there's some mayors who are really in denial, and that's going to be an issue."
The mayor of Gisborne, Meng Foon, disagreed with the paper's findings as far as his region was concerned.
He said given Gisborne's high population of youth, and the work underway to create jobs to keep them there, the region was set to grow.
"Whatever report that has come out to predict the future and decline is all a myth.
"In my term, we started off with a population of 42,000 and we're now at 47,900 ... we will definitely grow sustainably."
Kaipara mayor Greg Gent was optimistic about his region's future and growth.
"In the eastern side, in Mangawhai, we're issuing 30 building permits a month, so that is growing fast.
"And actually managing that growth is one of our biggest challenges as Auckland gets closer.
The future of the western side was equally positive, he said.
It was important to acknowledge the ageing population, which his region might benefit from.
A town such as Dargaville, with a population of 5000, had all the facilities an older population needed, he said.
"Older people can keep driving, for example, as there's less congestion compared to a bigger city. They can park right outside a shop they need to go to.
"I think it's going to have more appeal to the elderly - and that's great."
New Zealand First leader, Winston Peters has rubbished the report, calling it an "apology for the government's neglect".
"It is an academic piece which is utterly remote from the facts, doesn't seem to grasp what's going on in regional and provincial New Zealand, and thinks it can write a prescription which means that small towns will go on being ghost towns and be deserted.
"They're utterly wrong of course."
He said while many regions were in decline, they had a real future.
But he said that was reliant on the government investing in their development.
"If there is no planned support base to help the rural infrastructure and help the rural export base, then it will go on doing what it's doing now and be in decline.
"If you look at, for example, broadband extension... for every dollar they spend in the provinces, they're spending almost twice that amount in the big cities."
Mr Peters said many of the provinces were big exporters and would turn around if the New Zealand dollar fell.