SMC Bulletin - Irrigation efficiency woes

Published: Fri 24 Aug 2018 04:32 PM
Irrigation efficiency woes
It might seem like common sense that increasing the efficiency of irrigation would save water, but the equation isn't that simple.
In a Policy Forum published today in Science, international experts argue that increasing efficiency simply results in more water being used on farms and less being returned to the environment.
As Dr Brent Clothier from Plant & Food Research explained to the SMC, the irrigation efficiency paradox is that "any water saved by the individual farmers does not - global empirical evidence shows - serve to reduce water takes across the entire catchment". Instead, more people end up using the water. "So, individually, the farmers might well use water efficiently, but the total extraction of water by the whole community of farmers across the catchment is not reduced."
Not only is the water not 'saved' but it also reduces the amount of water being returned to the ground through leaks or other means. Dr Leanne Morgan from the Waterways Centre for Freshwater Management at the University of Canterbury told the SMC: "the reduced groundwater levels can impact spring flows and require farmers to lower wells (at considerable cost) to access the now deeper groundwater". She says this is an example of the "unintended consequences that might arise from irrigation efficiency initiatives designed to reduce water use."
We don't tend to think New Zealand has issues with water scarcity, but Professor Troy Baisden from the University of Waikato says because of the rapid expansion of dairy, wine and fruit into drier regions over the past few decades, "our freshwater available for irrigation is already fully allocated or over-allocated in these regions".
In an unrelated piece, Dr Mike Joy from Victoria University of Wellington wrote on Newsroom that irrigation dams like the one proposed for Waimea River in Nelson are a "dumb idea" as the "lock us all into a high-risk, high-cost, high-impact water storage system". For those upset at the Government's stance on irrigation, a recently-shelved irrigation scheme in the Waimate District has been revived by private backers.
The SMC gathered expert reaction on the Science article.
Quoted: Newsroom
"What we would like to see is the beginnings of a whole new industry built on sustainably-grown tōtara.
We would like to see more employment, we would like to see high quality jobs in Northland."
Scion’s general manager of research and investment Russell Burton on the viability of growing tōtara for timber.
Samurai to slay stink bug
Ramped up biosecurity controls have done a good job of keeping the dreaded brown marmorated stink bug out of the country. But should the one-dollar-coin-sized bugs gain entry to our greener pastures, the Environmental Protection Agency (EPA) has pre-approved the release of their traditional foe: the pin-head sized samurai wasp.
The bug has decimated crops in North America and poses one of the most significant biosecurity threats to our agricultural sector – particularly the kiwifruit and wine industries. It also has the potential to attack native plants like karaka and kowhai.
The EPA’s decision means they are only able to release the non-native samurai wasp if stink bugs slip through the border and invade. The samurai wasp is not the only biocontrol agent we have at our disposal. The EPA has previously released other parasitic wasps to control the agricultural pests like clover root weevil and coddling moth. However, this is the first time the EPA has given pre-approval to release a species into the country ahead of a threat, an advance the agency’s organism manager Stephen Cobb told Newsroom was “ground-breaking”.
“Bio-control is increasingly what the primary sector and people focused on conservation are looking at as it is considered possibly a bit more environmentally friendly than the use of pesticides or herbicides or chemicals,” said Cobb.
New Zealand winegrowers biosecurity manager and emergency response manager, Dr Edwin Massey, who is also a member of the Brown Marmorated Stink Bug Council previously told RNZ the samurai wasp is both a surveillance and control tool.
“The wasp favours brown marmorated stink bug eggs over any other stink bug egg, so releasing it only when there is a stink bug incursion is exactly the right thing to do.”
The Ministry for Primary Industry’s Dr Catherine Duthie told Newsroom: “We’ve got quite an arsenal lined up. This parasitoid [samurai wasp] is just one of those tools.” MPI is also preparing pheromone-laced traps to lure the stink bugs, a spray to kill them, and trained dogs to locate areas with bug infestations.
“Essentially the parasitoid is a mop-up measure to make sure that we don’t get any further adult or nymph brown marmorated stink bugs into the population.”
The decision was covered by local media.
Video workshops go South
In October, the Science Media Centre will take its popular science video making workshops to Christchurch and Dunedin.
These video workshops (produced in collaboration with Baz Caitcheon) focus on giving scientists the tools and skills to communicate their research in short videos aimed at an online audience.
Producing short videos using the high-definition camera built into your smartphone or tablet has never been easier. We’ll show you to how to develop a video concept and give you tips on the best ways to shoot, edit and distribute your video content. In the weeks following, Baz will mentor you to help you produce your first science video.
The workshops are free to attend, but limited to 15 places. This is a competitive application process – the best applicants will be selected based on the video concepts outlined in the application form.
Christchurch, University of Canterbury
WED, 24th October, 9.00am – 1.00pm
Dunedin, University of Otago
THURS, 25th October, 9.00am – 1.00pm
Science Media Centre
Our aim is to promote accurate, evidence-based reporting on science and technology by helping the media work more closely with the scientific community.
The Science Media Centre is New Zealand's only trusted, independent source of information for the media on all issues related to science. Thousands of news stories providing context from and quoting New Zealand researchers have been published as a direct result of our work.
Contact Science Media Centre
Postal Address:
PO Box 598, Wellington 6140

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