The mapping of Anglican believers in central Auckland for the study, based on the 2006 Census, found the highest concentration in the "wealthier suburbs" such as Remuera and Herne Bay but low in areas such as Avondale and Otahuhu.
Associate Professor Peter Lineham, who led the study, said this showed the church was "failing to connect" in areas with a high concentration of ethnic minorities.
"Any religion that did not engage wider than the rich, white middle-class will certainly not be growing in a city with Auckland's demographics of today," Dr Lineham said.
However, an increase in immigration of overseas Catholics was helping the Catholic church numbers in Auckland.
Dr Lineham said he believed the church was experiencing a similar decline as the other denominations, but those leaving the church were being replaced by Catholic migrants from Asia and the Pacific.
A National Church Life survey last year found nearly half the Auckland Catholic population was made up of Asians and Pacific Islanders. The survey found 30 per cent of those who went to Mass were Asians and 18 per cent were Pasifika, with just about half identifying with European ethnicities.
"The levels of activity of the Catholic church, the Mass attendance rate, show signs of a great deal of vitality especially among Filipinos, Koreans and Indians," Dr Lineham said. "I am astounded by how multicultural the Catholic Church is in Auckland, and how they are evenly spread across the city."
He estimated Catholics in Auckland to be about 12 per cent of the population and Anglicans having dropped to less than 10 per cent.
"It is very likely that the next census will show Catholic numbers to be ahead of Anglicans for the very first time."
The only Christian sector that is seeing a slight increase are the independent churches, sects, evangelicals and pentecostals, which Dr Lineham attributes to "better marketing and online presence" and "ability to connect with the young".
"What we are seeing is an increasing number of people who do their church shopping online, from home," he said.
Dr Lineham said it was common for Christians in Auckland to attend more than one church and practice more than one faith, and the offerings of yoga and meditation were connecting New Zealanders to new spiritual movements.
Next year's census is also likely to reveal that those identifying with lesser-known faiths like the Jains, Bahais, Zoroastrians and Hare Krishna have increased, he said.
Dr Lineham said Asian migration had had an "incredible effect" on Auckland religions, with many Korean and Chinese Christian groups having integrated and even taken over churches on the North Shore and the Eastern suburbs.
Temples like Fo Guang Shan, built over 3.6ha in Botany, and the $8 million Sikh Gudwara in Takanini, were also changing the landscape of the city.
"No longer are these small embattled communities, they are active and engaged and unashamed," he said. "The level of activity, mosques, temples, synagogues and shrines, is now much more evident in the community."
In Auckland, Hindus number 3.5 per cent of the population and 2.2 per cent are Buddhists, higher than the number of Baptists or Latter-Day Saints. Nearly one out of 10 Aucklanders said they were followers of other religions in Dr Lineham's study - nearly twice the national average of 5.1 per cent. But the number of those who say they have no religion has also increased, which Dr Lineham says is partly because of an increase in immigration from communist China and secular Europe.
Father Larry Rustia, assistant parish priest at St Mary's Catholic Church in Northcote, said having chaplains for migrant communities and different ethnic masses had helped the church remain relevant.
"We have chaplains for different ethnic groups, and we do have masses in different languages," Father Rustia said. "But I also think the main attraction of the Catholic Church for migrants is that we are open to everyone."
The percentage of Catholics in Auckland is higher than elsewhere in New Zealand.
"Being outside of their own country, migrants are looking for a place where they can belong ... they can feel a sense of belonging in the Catholic church," he said.
Hindu, which has spiked from 0.004 per cent in 1986 to 3.5 per cent in 2006, is the largest "other religion" in the city.
Ravin Kotak, religious committee chairman of the Bharatiya Mandir Temple on Balmoral Rd, said an increase in international students and migrants from south and southeast Asia had helped boost numbers.
Mr Kotak said 10 years ago the temple played a large part in helping him start life in New Zealand, and many immigrants regarded the temple as a "second home" and more than just a place of worship.
But within each of these new religions, there are also complex divisions and diversity. An Asia New Zealand Foundation study on "Diverse Auckland" found that within the Hindu population, regional and linguistic groups were "increasingly celebrating their own festivals".
"Prominent among these celebrations are the Durga puja by the Bengalis, Kavadi by the Tamils, Onam and Vishnu by the Malayalees, and Ganesh Chaturthi by the Marathis."
The series
The Immigration Act 1987 radically changed the criteria for migrant entry to New Zealand, resulting in a surge in people coming from non-traditional source countries. This week, the Herald looks at how these migrant communities have changed Auckland.
Yesterday: Population - the changes and how comfortable are we?
Today: Religion - Christianity vs new religions
Tomorrow: Food - from caffe latte to teh tarik
Thursday: Sports - tapping on migrant talent
Friday: Festivals - changing the way we celebrate.
