What a dry winter would mean for the ag/hort sector – and for the country

New Zealand may be heading into a dry winter following a month of near record-breaking dry patches across the country.

What are the flow-on effects if insufficient rain falls during the cold season?

The Science Media Centre asked experts to comment on how the potential dry season may affect …

  • Rural communities and agriculture
  • Hydro energy production
  • The environment

These experts have responded:

Dr Nick Cradock-Henry, Senior Scientist, Manaaki Whenua – Landcare Research:

“The prospect of higher-than-average temperatures and lower rainfall than normal, for parts of the South Island, highlight again, the climate-related challenges for primary industries and rural communities. For example, drought has been a recurring feature of farming in North Canterbury over the last decade, overlapping with both the Kaikoura-Marlborough-Hurunui earthquake (2016) and Mycoplasma Bovis (M. bovis), a bacterial disease affecting dairy and beef cattle, which resulted in a major biosecurity hazard and response (2017).

“Farms are often set up to cope with one, or even two, ‘difficult years.’ Repeated, or prolonged dry conditions, however, exacerbate existing vulnerabilities, placing undue pressure on household finances, personal relationships, livestock, and other aspects of the production system.

“Furthermore, these effects have inter-seasonal implications. Resilience is often described in terms of the ability to withstand or recover from shock. When the fundamental social, economic, and environmental capitals on which these communities depend becomes slowly eroded through successive or prolonged dry conditions, recovery can be difficult.

“With climate change, Aotearoa-New Zealand is likely to face hotter, drier conditions. Understanding the ways in which rural communities are exposed and sensitive to current impacts, can help inform strategies aimed at reducing future vulnerability.”

  • Conflict of interest statement: “Nick Cradock-Henry currently leads funded research supported by Ministry for Primary Industries through the Sustainable Land Management and Climate Change (SLMACC) programme and the Ministry of Business and Innovation – Resilience to Nature’s Challenges Kia Manawaroa – Ngā Akina o Te Ao Tūroa National Science Challenge (Contract No. C05X1909).”

Bill Kaye-Blake, Principal Economist, New Zealand Institute of Economic Research:

“Rural communities are resilient in different ways. Some rely on strong social networks, some can draw on a richer economic base.

“We see this in the way people react to drought. In the 2019-2020 drought, we saw evidence that farmers with money solved their problems by buying in feed. By contrast, farmers with strong social networks helped each other connect with sources of feed.

“Industry organisations were part of the solution, too. They helped connect people, and they also provide good feed planning tools.

“The biggest challenges are for people who are a bit more isolated. For example, people on lifestyle blocks may have a few animals but may not be well connected in the farming community. They can struggle to find supplemental feed for their animals.”

  • No conflict of interest

Professor Justin Hodgkiss, School of Chemical and Physical Sciences, Victoria University of Wellington, and Co-Director, MacDiarmid Institute for Advanced Materials and Nanotechnology:

“’The dry winter problem is a key vulnerability in New Zealand’s transition towards a zero-carbon economy, such is our dependence on hydroelectricity generation. Without additional renewable energy generation and storage capacity, dry winters mean that coal and gas is required to meet our winter electricity demands – a significant setback for our climate commitments.

“Moreover, we can expect the frequency and impact of dry winters to become more challenging in the future – due to climate change, as well as the growing demands from electrifying transport and industry. It is imperative that we continue to build and diversify our renewable energy generation capacity for a range of climate conditions, along with long-term energy storage options such as hydrogen or pumped hydro storage.”

  • Conflict of interest statement: “The MacDiarmid Institute is developing new materials for renewable energy applications, including Prof. Hodgkiss’ own research in solar photovoltaic materials.”

Ralph Sims, Professor Emeritus, Sustainable Energy and Climate Mitigation, Massey University:

“Climate scientists have told us for decades to expect more dry years – this could be one of them.

On Tuesday afternoon (4 May), South Island hydro was running at around half its full capacity and North Island hydro about one quarter. Geothermal was near full capacity, North Island gas around a third, but wind power only around 20 per cent. Yet it was a windy day. Solar was too small to show, and the coal / gas plant (Huntley) was running at full capacity. Hence, renewable electricity generation was down to nearly 70 per cent of total generation compared to the usual level of over 80 per cent.

“There is no doubt the South Island lakes are low – I cycled past some a week ago – and they may well get lower. But why so much coal? The electricity market could argue it is currently cheaper in the ‘merit order’ than wind, and selecting generation plants based on minimising carbon emissions across the electricity sector is not yet a priority.

“We know we have to stop burning coal and gas sooner rather than later. We know dry years will become more common as a result of climate change – and this will also impact on agriculture. So, as well as building more renewable electricity plants, we will also have to modify the market as well as make the grid more flexible on the demand-side.

“As an example, the aluminium smelter is currently being paid to reduce its power demand for a few weeks. Other organisations, such as cool stores, can do the same to offset peak demands. However, everyone can play their part by saving electricity at home and at work – and therefore also save money too.

“The developed world has become a wasteful society– not just electricity and fuels, but also food and water – and this cannot continue. We should all know by now how to use energy wisely given all the publicity and advice given over recent years.

“Now is a good time for the team of five million to put it into practice. We will have more dry years. We will need to build more renewable power plants. But we also need to improve energy efficiency. It reduces wastage, helps electricity generators and system operator Transpower to meet the fluctuating demand at any given time – especially in a dry year – AND it saves money too.”

  • No conflict of interest.

Dr Cate Macinnis-Ng, Associate Professor and Rutherford Discovery Fellow, University of Auckland; and Principal Investigator and Theme Co-Leader, Te Pūnaha Matatini:

“Our ongoing monitoring of hydrology of kauri forest at the Huapai Scientific Reserve in west Auckland shows winter replenishment of soil moisture is an important part of the forest water cycle. We have found our study species (kauri, rewarewa, totara and tanekaha) have good adaptations for drought survival, but reductions in soil moisture (as happen in drought) have impacts on the water and carbon cycles of the forest.

“We had a severe drought in early 2020 and summer 2021 was also reasonably dry. We are finding the trees respond to dry soil by slowing transpiration (tree water use) and we are investigating what impact this has on carbon uptake of the trees. The leaf pores that allow water to leave a plant often close under drought, but these pores (known as stomata) also allow carbon dioxide into a plant for photosynthesis (the process of carbon uptake).

“We expect drought is slowing carbon uptake of native forests, but we don’t how much yet. If forest soils don’t replenish their water stores over winter, this slowing is likely to be exacerbated the following spring and summer.

“Furthermore, warmer winter temperatures will drive higher evaporative demand in the air, potentially increasing transpiration and further drying soils. This is all a work-in-progress for our team working on drought impacts in native forests.”

  • Conflict of interest statement: “I have current funding from MBIE, New Zealand’s Biological Heritage NSC and my Rutherford Discovery Fellowship.”

Source:  Science Media Centre

Author: Bob Edlin

Editor of AgScience Magazine and Editor of the AgScience Blog