She said Whangarei was the eighth largest district in New Zealand with its population projected to reach 110,000 by 2043.
However, it would need to attract or retain more people in the "working age/reproductive age cohorts" (15-45 yrs) or the district would have mostly elderly residents by 2045.
"Even though we have quite a high number of young people (12 per cent were aged 15-24) we have fewer post-secondary education opportunities than other districts so many of our young people tend to leave the district for work or education," she said.
"We have fewer in the working and reproductive age (21.9 per cent were aged 25-44 years), and these are the people who are key to sustaining growth and development into the future.
"They seek opportunities and vibrancy in the place they live - so improving those aspects of our district will help to attract and retain them."
Whangarei has slightly more older people than the national average.
Northland and Whangarei's populations were ageing much more rapidly than the New Zealand average, particularly the 65+ group, while the 25-44-year-old group was dropping more rapidly than the NZ average.
She said the future economy of Whangarei could suffer due to the lack of younger, enterprising people. The lack of younger people would result in labour shortages in the future. She said Japan is one example where its ageing population is impacting on the economy.
Ms Seutter said the number of people 65+ years had grown by 45 per cent in the last 12 years.
The district had grown at a rate of about 1000 people a year for the past seven years, especially in the lifestyle areas west of Maunu, around Marsden Point and Kamo West, with people moving from the inner city to coastal, rural and rural residential areas.
The largest increases are in Three Mile Bush, Te Hihi and Marsden Point. Meanwhile, people were leaving areas such as Otangarei, Port/Limeburners and Whangarei Central.
Most migrants come from Auckland, the Far North and Kaipara, while most overseas residents were born in the UK and Ireland (43 per cent). International residents also hailed from Asia (15 per cent) Europe (11 per cent), Australia (10 per cent) and the Middle East/ Latin America/Africa (10%). She said 69 per cent of overseas migrants were of working age (15-64).