"Significant" challenges have been forecast for Tauranga and the Western Bay district with the area's total population expected to grow to nearly 270,000 in the next 27 years.
In 2018, the Census estimated 142,100 people lived in Tauranga City and 53,300 in the Western Bay of Plenty. Collectively, these populationswere expected to grow by 20,000 in the next two years.
But new projections obtained by the Bay of Plenty Times from Statistics New Zealand reveal Tauranga's population is predicted to soar 57,000 to reach 199,100 and Western Bay's by 14,700 to reach 68,000 by 2048 — making a total of 267,100.
However, a Massey University professor said he was cautious about the projections as he believed Covid-19 would depress fertility rates and completely change migration.
Tauranga was originally an area of small coastal centres but has become New Zealand's fifth-largest city in New Zealand. The figures show the city will remain ranked the fifth-largest in 2048.
The population of the wider Bay of Plenty region is expected to increase 84,000 to 408,430 in the same timeframe, Rotorua is predicted to grow 10,000 to reach 84,800 and the country could hit 6 million.
As the numbers grow, some of those who've lived here the longest have almost forgotten what the city use to be like.
Business owner Barry Muir, 81, moved to Greerton in 1948 and went to Greerton Village School, which only had one classroom at the time.
Muir remembered a shop had opened up in 1954 on Chadwick Rd across the road from a grocery store called Thriftway - "and that was all that was about there".
There was no bridge between Tauranga and Mount Maunganui, and getting between each area meant a drive around the "long way" through Welcome Bay, or on a ferry that ran regularly.
"Pāpāmoa, I don't even think there was a tarseal road in parts of it."
Muir now lives in Mount Maunganui and said the area was losing its feeling of a camping holiday spot and tents had been replaced by houses, apartments, and hotels.
"You could camp on The Mall ... now we're a big city."
"It's just mushroomed ... it's a great place to live, and that's why people want to come here."
Muir said more people meant larger shopping centres, like Bayfair, had affected the strip-type shopping which he felt at his business on Maunganui Rd - Furniture Gallery.
However, he said the booming numbers meant businesses should look at it as an opportunity.
SmartGrowth strategic adviser Ken Tremaine said the biggest challenge would be land being released by the authorities and finding areas for redevelopment.
However, there are "significant" challenges and investment will continue to be an issue, he said.
"The growth is only really post-World War II. It started off as quite small coastal centres."
More people meant more cars on the road, more houses and schools were needed, there was more pressure on the health system, effects on water quality, and more land needed for employment.
He said 27 years was not far away, and they were currently working on releasing land from the Government and working on areas for regeneration.
All of this needed to be managed within the scope of managing climate change at a local level which meant keeping everything as compact as possible to minimise traffic.
The figures weren't surprising, he said, and the agency which has been around for 20 years has always had high growth forecasts.
On the flip side, more people meant a larger range of employment, more recreation centres and parks, tertiary education growth, and more diversity.
Massey University Professor Paul Spoonley said he was cautious about the projections as he believed Covid-19 would depress fertility rates and completely change migration.
However, he said there were a few things that would stay the same for Tauranga being a "premium" retirement destination.
Auckland's population boom in that time was also expected to see the spill from the largest city seep into Tauranga.
He said the city would benefit from more people moving to the city creating more jobs and driving economic development, and particularly new jobs, and it would continue to be a "premium" retirement destination.
It was also being sought out as desirable place for a place to be with new ways of working, such as working from home, created by the pandemic.
Western Bay of Plenty mayor Garry Webber said managing and accommodating the population increase was being done by SmartGrowth.
Business opportunities at the Port of Tauranga, in the kiwifruit industry, and the desirability of the Western Bay subregion sat behind the organisation's expectations the growth would continue.
Webber said while there were always hurdles, "growth is the best position to be in".
A decline in anything "is not really a good option", he said.