Herald on Sunday editorial: Cities encroaching on our best soil

We must keep our market gardens in good shape.

Food security sounds like a quaint concern in age of global trade. Fresh meat, fish, fruit and vegetables are flown around the world. Every week our supermarkets display produce from numerous different countries.

Yet national food security remains important to most people. Everyone likes to think their own country has enough food to sustain its population if it had to.

New Zealanders probably imagine theirs is one of the last countries that needs to worry on that score. Indeed, our food exporters are constantly battling the food security concerns of other countries that cause them to protect or subsidise their own farmers in competition with our products.

"There is no need," we tell them, "we will never refuse to supply you."

But our feature of the subject today suggests that even Kiwis want food security, and climate change is giving them reason to worry about it.

Climate change means countries are not just getting warmer, they are getting more extremes of wet and dry weather and bigger storms. Just this summer, some regions have suffered drought, followed by unusually heavy rainfall from tropical cyclones. Plant growth has been disrupted, crops destroyed.

The results were seen in prices of vegetables. In November a group of doctors warned in the Medical Journal that low income households could not afford to eat properly. Instead of greens on their plate, those children are being given instant noodles and white bread.

High prices may be a temporary problem but the horticultural industry believes New Zealand's local supply could be permanently threatened by the loss of suitable land to housing. Auckland is spreading ever further on to the fine horticultural soils south of the Manukau.

Contrary to the impression we get in supermarkets we import very little fresh produce, according to Horticulture NZ. Just about all our supply of staples such as carrots, onions and potatoes is grown here.

They estimate that only 5.5 per cent of the country is suitable for crops, and only 1 per cent is used for horticulture. They want the rest of the suitable land secured for the purpose in the event of climate change.

A warmer climate, wetter in some places, drier in others, is likely to see some crops no longer viable, new crops arrive and New Zealanders may be eating just as well in the long run.

But it could be a stormy road from here to there. We must keep our market gardens in good shape.