Canterbury's dairy industry is booming, leading the sector's growth as national dairy cow numbers continue to surge.
However, more cows and more-intense dairying have raised concern over their effect on the region's waterways.
Statistics New Zealand figures show the dairy cow population in New Zealand has risen 5 per cent in the past year to 6.5 million, while sheep are steady, about 31 million.
The cattle numbers are up more than a million since the previous survey in 2007, while sheep have fallen by 7.3 million.
In 2007, there were nine sheep for every New Zealander, but in 2012 this has dropped to seven.
DairyNZ senior economist Matthew Newman said Canterbury's dairy industry had experienced "phenomenal growth" in the past five years.
Its statistics showed that in 2007 Canterbury had 13 per cent (518,000) of the country's milking cows.
By 2011-12, that had risen to 16 per cent (753,000 cows), producing 17.7 per cent of New Zealand's milk.
"That's a very significant amount of milk coming out of Canterbury," Newman said.
"[It] has been the largest growth region for New Zealand for the last decade."
That looked set to continue, with Newman forecasting more than 800,000 cows would be milked in Canterbury by next year.
Significant changes to the environmental laws could hamper the dairy industry's growth, Newman said.
Environment Canterbury's proposed new land and water plan details stricter controls on land use and effluent run-off.
Commissioner David Caygill said the plan was "partly a response to the increase in farming intensity."
"[The plan] will be a completely new set of rules on how land can be used and how that affects the environment. It is ECan's job to protect the waterways and we will."
A public hearing would be held through February-July on ECan's plan and the decisions brought into force in 2014.
Federated Farmers dairy chairman Willy Leferink was confident the boom would not cause any pollution problems.
"I was on the plane the other day speaking to a guy about all these cows and he said ‘They're all just going to poo in the river" and I said to him: "The current cows don't poo in the river and these ones won't either".
The extra money brought into the economy by the dairy cows could also be reinvested to benefit the environment, Leferink said.
Statistics NZ agricultural manager Hamish Hill said strong international demand for dairy products was also propelling the cow increase.
Dairy exporter Fonterra's milk solids price increased from $4.05 a kilogram in January 2007 to a record high of $7.95 in April 2011.
It was still relatively high at $6.
The value of dairy exports had also shot up during the past five years, with exports increasing 72 per cent to $12.5 billion since 2007.
- © Fairfax NZ News
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