Till your well runs dry: NZ drought hits record levels

By Gareth Renowden 11/03/2013


Australia may have had an extraordinary “Angry Summer“, but New Zealand’s been having a bit of a cracker too. Prolonged warm and sunny weather over much of the country has driven North Island soil moisture deficits to levels not seen for at least 70 years (see map at left). Official drought status — which means farmers are eligible for various forms of government assistance — has been declared in Northland, South Auckland, Coromandel, Bay of Plenty, Waikato, and Hawke’s Bay. The Manawatu and Rangitikei regions have also asked government for drought status. Most of the North Island is also subject to total fire bans — another first for this dusty summer. Preliminary estimates of economic losses are already heading towards $1 billion.

Stuff.co.nz noted the obvious climate connection:

Long, dry spells are forecast to double by 2040 as temperatures continue to rise and New Zealand heads towards a more Mediterranean climate.

Experts warn it could spell the end for farming as we know it and may cost the country billions of dollars in drought relief each year before practices are adjusted.

“This is historic,” said climate scientist Jim Salinger, who has calculated that the amount of rain needed for grass growth was the highest since records began. “It’s like comparing your income against expenditure in your cheque book. And we are in deficit.”

Jim Renwick, in an opinion piece for The Press noted:

Looking to the future, the risk of drought in New Zealand is on the rise. The persistent high pressure systems typical of the subtropics are already moving our way and this trend looks set to continue. The “subtropical high pressure belt” is where the world’s deserts are located, and that belt is edging our way as the tropical region expands outwards under a warming climate.

Combine that with higher temperatures, increased evaporation, lower soil moisture, and we have a recipe for at least doubling the risk of drought in many of the drier parts of the country by late this century, possibly by mid-century in places. A recent report for the Ministry of Primary Industries projected an increase in drought occurrence for almost all of the country, even under an optimistic scenario for greenhouse gas emissions.

We’ve certainly been getting persistent high pressure systems. This surface pressure anomaly plot for the NZ region from mid January to a few days ago1 shows that a substantial blob of high pressure has been parked over us.

NZdroughtNCEPpressure201301

The MetService blog has a (much) more detailed explanation of what’s been going on in the southern hemisphere’s atmosphere here.

Meanwhile, politicians have begun to reflect on the realities of the forecast of droughts happening more often — warning that “continued drought support might be unsustainable“:

Finance Minister [Bill] English, standing in for John Key while he is visiting Latin America, said that while the Government was providing support now, this may not be sustainable if severe droughts became regular events.

“If there’s going to be more droughts, more regularly, farming practices will simply have to adapt,” he told TVNZ’s Breakfast.

“We’ve got research in place for instance to find more drought resistant grasses and farmers have for years been adapting their management practices.

“That would have to continue because . . . Government simply can’t support them to maintain practices in the face of continuous droughts, if that’s what happens.”

If that’s what happens? The government knows exactly what NIWA’s modelling of future climate has to say about the likelihood of increased frequency and severity of droughts, and has done for years. A prudent government might have done some thinking about risk and sensible strategies for the future, and considered the wisdom of encouraging diversification away from water intensive and drought sensitive agricultural systems such as dairying.

Unfortunately, our government has preferred to gut the emissions trading scheme and dismember all but the bare bones of a rational national response to the climate challenge. By delaying a carbon price signal for agriculture, the government locks the near term NZ economy into high carbon, high water use agricultural systems — the very worst outcome.

Meanwhile, the drought isn’t all bad news. Looking beyond the bones of the cow’s arse, the national grape harvest is looking good (perhaps great)2, and apple growers aren’t complaining either. That’s what diversification and adaptation are all about…

[Peter Tosh]

  1. From the Earth System Research Lab’s NCEP reanalysis operational plotting page.
  2. The nets are on, and there’s a potentially exciting crop of pinot noir ripening at Limestone Hills — the last thing I want is drought-breaking rain, at least not before the main harvest is in (mid April in Waipara).