28 Sep 2022

The fragile magic of highly productive land

From The Detail, 5:00 am on 28 September 2022

The government's unveiled plans to beef up protection of highly productive land. The Detail looks at why it's needed.

Lettuce crops being grown in market gardens in Pukekohe.

Lettuce crops being grown in market gardens in Pukekohe. Photo: RNZ/ Brad White

Not all land is created equal.

Some - which we call 'highly productive land' - is, as it says on the tin, highly productive.

That means it's much more flexible than other types of land: you can grow many different types of fruit or vegetables on it; you can adapt it for other types of farming, all with minimal input from farmers.

Aotearoa puts its highly productive land to good use: in breadbaskets, like Pukekohe, we grow food that feeds New Zealanders, and is exported around the world. 

About 60 percent of the world's radish seed is grown in Aotearoa, as well as 40 percent of the world's carrot seed and 50 percent of the white clover seed. 

And that dextrous soil allows us to alter our produce to reflect trends in global markets, to pivot away from low-value exports, and towards high-value ones. 

Highly productive land is valuable. This is partly due to its scarcity - only about 15 percent of Aotearoa's total land area is categorised as highly-productive - and just 1 percent is the highest tier of productivity.

It's also partly due to its fragility: once you've built something on highly-productive land - a building, for example - you can't just knock the building down 30 years later and expect the land to retain its characteristics.

"It's very, very hard to recover degraded soil," says Sam Carrick, a soil scientist at Manaaki Whenua/Landcare Research.

"There is a lot of land modification - anyone who goes past a subdivision will see the degree of land modification that's going on.

"So, generally, once it's gone into urban use it's very very hard for it to come back into food production down the track."

This has become a particularly pertinent issue over the past couple of decades: as New Zealand's shortage of housing grew more acute during the 2000s and 2010s, vast tracts of highly productive land were repurposed for housing and lifestyle blocks - more than 200,000 hectares from 2002-2021.

All these factors led to the government's decision this month to introduce a new national policy statement, strengthening protections around highly productive land. 

Councils will now need to identify, map and manage productive land to protect it from inappropriate use and development, though they can still make it available for housing if there's no alternative, or if certain tests are met.

Carrick says he's in support of the idea, which many fruit and vegetable growers have been agitating for for years. 

"We've seen by those numbers...that we need to be really careful going into the future.

"This is not just for us today - we're managing the land for future generations...and with a changing climate, where we're growing our food will change. We need those options up our sleeve."

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