Drought will bring more crop disease, scientists warn

New Zealand’s land-based primary industries need to get ready for increasingly serious crop disease as climate change causes more and longer droughts, according to new research.

In the journal Australasian Plant Pathology, the authors of the study say climate change is expected to bring more droughts in many parts of New Zealand, and more droughts are “likely to increase the severity of a wide range of diseases affecting the plant-based productive sectors”.

Scientists from the Bio-Protection Research Centre, Scion, Lincoln University, AUT University, Landcare Research and the University of Auckland analysed the potential impact of climate-change-induced drought on several commercial plants and their diseases.

They found that in most instances “increased drought is expected to increase disease expression”.

The probable negative effects of drought include

“…a predisposition of hosts to infection through general weakening and/or suppressed disease resistance”. More frequent and more severe droughts could also lead to “emergence of enhanced or new diseases of plants that can reduce primary production”.

New plant disease pressures are expected to occur

“… with potentially devastating impacts for New Zealand’s productive sectors.”

But the news is not all bad.

“Drought may reduce the severity of some diseases, such as Sclerotina rot of kiwifruit and red needle cast (RNC) of radiata pine,” the scientists said.

And in some cases it could “activate systemic defence mechanisms resulting in increased resistance to infection”.

In an extended case study the authors said that the effects of increased drought on New Zealand’s Pinus radiata industry would depend on many factors, including whether drought happened early or late in the season.

“There is urgent need to study the impacts of the different levels of drought and different levels of RNC severity to understand the thresholds at which radiata pine plantations would still accomplish their economic and ecological roles.”

Lead author Dr Steve Wakelin, of the Bio-Protection Research Centre and Scion, said it was essential that more research was carried out so each industry could prepare for the effects of drought.

“Many industries, such as agriculture and horticulture, may have time to gradually change over the next 20 or 30 years, to avoid the worst effects of drought or even take advantage of any opportunities the changing climate may bring.

“However, plantation forestry does not have the luxury of flexibility. What is planted now will need to not just survive but thrive in whatever climate and disease conditions are prevailing in the next 20, 30, or 40 years.

“It’s essential that primary industries with a long production cycle start assessing and addressing the risks and opportunities a much drier climate will bring.”

***

Wakelin, S.A., Gomez-Gallego, M., Jones, E. et al. Climate change induced drought impacts on plant diseases in New Zealand Australasian Plant Pathol. (2018) 47: 101.

Source: Bioprotection Research Centre

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Cape Town – or will the hydro-illogical circle make it the cape of good hope?

Cape Town is grappling with a severe water shortage. 

Plant & Food principal scientist Brent Clothier has emailed colleagues on the drought in the Western Cape province of South Africa which began in 2015.

At the sharp end of this drought is Cape Town. Clothier says Wikipedia has “a nice up-to-date assessment of the crisis” here.

 Despite water saving measures, dam levels are predicted to decline to critically low levels, and the city has made plans for “Day Zero” on 4 June 2018^[1], when municipal water supply will largely be shut off. If this happens, Cape Town will be the first major city to run out of water.^[2]

 
The only good news is that Day Zero has been extended to June 4 from May 11.

The delay has been attributed to the continued decline in agricultural usage and Capetonians reducing their water usage, said deputy mayor Ian Neilson.

The week’s average daily production of all water sources at the time of the extension – February 13 – was at 526Ml/day, above the target of 450Ml.

“Team Cape Town, we are getting there. We now need to see how low we can go to ensure that we stretch our water supplies as far as possible into the winter months by reaching the 450 million litre per day collective consumption target which equates to 50 litres per person per day,” said Nielson.

Meanwhile, the national government has declared the drought affecting the southern and western areas of South Africa a national disaster.

Clothier reckons “Day Zero” is almost a certainty, because there’s unlikely to be any rains before June.

Even before “Day Zero”, the drought has had major impact because

“… in response to the water shortage, the agricultural sector reduced water consumption by 50 percent, contributing to the loss of 37,000 jobs in the sector nationally, and leading to an estimated 50,000 being pushed below the poverty line due to job losses and inflation due to increases in the price of food. By February 2018 the agricultural sector had incurred R14 billion (US$1.17 billion) in losses due to the water shortage.”

Clothier asks whether such an outcome could have been foreseen?

His email includes this graph of the reservoir water-storage capacity for Cape Town, showing the race-to-the-bottom down to “Day Zero”.

Clothier comments:

It highlights something about the human condition which just offers a ‘shoulder-shrug and a hope-for-the-best’ response in the face of climate change.

We could change our ways, and adapt to the new norms.

Here’s the reason why we don’t adapt.  It’s because we believe in the “hydro-illogical cycle”.  …

 

Clothier explains this is a contemporary ‘perversion’ of Leonardo da Vinci’s first iteration of the ‘hydrological cycle’! [Check out http://www.eco-innovation.net/fr/node/11260.]

 

Drought classification is extended to the Grey and Buller districts

Agriculture and Rural Minister Damien O’Connor has added the Grey and Buller districts on the South Island’s West Coast to the medium-scale drought declared in the lower North Island last month. 

The extension of the drought classification means the local Rural Support Trust and other recovery organisations get a funding boost of up to $50,000 to help their local communities.

O’Connor declared 13 districts across Taranaki, Manawatu-Whanganui and Wellington were in drought conditions just before Christmas after an extremely dry start to the summer. 

“On the back of an extremely wet winter that left many farmers unable to grow pasture or crops for spring, the early and unusual dry start to summer turned West Coast pastures from swamp to concrete,” O’Connor said.

“It was agreed that while farmers needed to plan for the worst, there was hope that the forecast rainstorms could break the drought before central government assistance became necessary. However, the Grey and Buller districts now meet the criteria for a medium-scale event.”

O’Connor, who is also the local MP for West Coast-Tasman, had been closely monitoring the dry-weather conditions in the lead-up to declaring the medium-scale event and today said there’s a watching brief on neighbouring areas including Murchison, which have missed out on rain. 

The Ministry for Primary Industries classifies medium-scale events as those that impact farms and communities at a district or multi-district level.

Central government aid includes tax relief and income assistance. The ministry is reviewing its drought policy framework with a new policy expected to be in place by the middle of this year. 

The New York Times and a natural-capital approach to water management

Brent Clothier’s group bulletin includes an item of interest to NZIAHS members and readers of this blog based on an article in the New York Times. He writes: 

It has been said of Californians that they “… love water, but hate rain”.

That conundrum is biting them now. The west of the US is in the grips of a massive drought, with a bleak outlook. Not because of the lack of rain ironically. But it is due to climate change which has progressively melted the snowpack which controls the bulk of the supply of water into Californian catchments.

So how do you make sense of the natural capital value of water?

Mark Bittman, a New York Times op-ed writer, recently advocated an opinion here:

Bittman gets straight to the nub of the problem

“Almost every number used to analyze California’s drought can be debated, but this can be safely said: No level of restrictions on residential use can solve the problem. The solution lies with agriculture, which consumes more than its fair share.”

He went on to contend  that

“… more water was used to grow almonds in 2013 than was used by all homes and businesses in San Francisco and Los Angeles put together. Even worse, most of those almonds are then exported — which means, effectively, that we are exporting water. Unless you’re the person making money off this, that’s just nuts.”

And then he says

“… the big question is not, “How do we survive the drought?” — which could well be the new normal — but, “How do we allocate water sensibly?” California grows fruits and vegetables for everyone; that’s a good thing. It would be an even better thing, however, if some of that production shifted to places like Iowa, once a leading grower of produce.”

So what are the crops that need to be considered?

Bittman shows that

“… California grows alfalfa (which uses more water in total than any other crop — yes, more than almonds) that then gets shipped to China. It grows lettuce in the desert, and other crops in places that make no sense. The state has also become the biggest dairy producer in the country; at least a part of that industry would work better back east, where both water and land are available. “

Bittman steers his readers to these numbers for agriculture (sorry about the imperial units) …

But….

“It won’t be easy to rationalize water use in the face of powerful water-dependent interests; though agriculture is a surprisingly minuscule part of the state’s gross domestic product, it’s a big political force.”

Yet…

“.In most areas, groundwater for landowners is “free,” as long as you can dig a well that’s deep enough. This has led to a race to the bottom: New, super-deep wells, usually drilled at great expense, are causing existing shallower wells, often owned by people with less money, to run dry.”

And truly the water is running out …

They’re sucking on…

“Groundwater that’s built up over a millennium which is being removed too rapidly to be recharged. Those aquifers will most likely never be replenished, making this a form of environmental suicide.”

Bittman’s  answer is that…

”It would be better to have a national policy preventing profit-making from public water and to encourage agriculture where it’s more naturally supported by the climate.”

It sounds like the NYT writer is advocating a natural-capital approach to manage our collective utilisation of the ecosystem services that our landscapes provide us. Good stuff. Politically tough – but it’s really the only way forward.

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* Dr Brent Clothier is Science Group Leader, Production Footprints & Biometrics Sustainable Production, at Plant & Food Research