Mr Collins said research showed that Northland's population was not going to grow dramatically over coming decades, so other measures were needed to grow the economy.
"Part of this decision is future-proofing things. It's going to be in place for the next 30 years or so, so it's for the future rather than just now," he said.
"We can't just grow our way towards prosperity because we aren't going to have a population growing to the extent that we might want. So we need to examine how we do things and find other ways to prosper and this is one of the ways to do that."
Mr Collins said it was an unrealistic expectation that reorganisation would lead to lower rates, despite a forecasted $5-$10 million a year saving. He said it was important that the existing councils carried on their work until the unitary authority elections in 2015.
"What we want from local government is to deliver the services they are there to deliver. It's important that the councils carry on with business as usual and still work on their long-term plans and any major projects they've planned. They can't just sit on their hands for two years."