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Dryland Canterbury?

- September 2020

The Canterbury Plains, known for its' Dryland Agriculture. Historic ways of farming the landscape going back generations. Old pasture species, old methods that have been tried and tested through 150 winters; and 150 summers - hot, dry summers at that.


However, over the last 20 years, vast swaths of bright green have invaded the often parched and golden paddocks. This bright green can be attributed to new pasture types (Clover/Ryegrass mixes) and more importantly irrigation; often circular in shape, this is due to a type of irrigation called Center-Pivot irrigation. Seen on the map above as bright blue circles, center-pivot irrigators now pepper the landscape; supplementing any rainfall that falls in the area.

{Map content: Irrigation of the Canterbury Plains; Rakia River through the centre of the frame; west of Te Waihora, Lake Ellesmere; Whakamatau, Lake Coleridge top left; the township of Ashburton bottom centre.}


On average 604mm of rain falls in Christchurch, the largest city in the South Island, the second-largest in Aotearoa, New Zealand.

Gravel and sand washed off the Southern Alps and deposited across the floodplains of Canterbury's famous braided rivers create the majority of Canterbury's soils. Just like sand at the beach or in a sandpit, these soils struggle to hold on to any rainfall as well as any additional irrigation - thus, continue to require more irrigation to keep the paddock at an optimal growing condition (field capacity). This creates a vicious cycle where the landscape, more importantly, the pasture, constantly needs more water. Groundwater is predominantly used in this system, sucked out of the gravelly soils, and spread across the landscape. As the groundwater is sucked out of the ground, the water levels in the rivers start to fall as their water rushes through those same gravels to fill the space left behind.

The main driver of this change from Dryland Agriculture to Irrigation has been the conversion of the Canterbury Plains from predominantly sheep farms to now dairy farms. A formula has been copied and pasted across the country, where Clover and Ryegrass replace the Cocksfoot and Tall Fescue of old, and the paddocks are sprayed with water to keep these new dought-hating pasture species happy. 


The change from sheep farms to dairy farms has also lead to more contaminants, nitrate (NO3-), and e. Coli being flushed into the sandy, gravelly soils, and either back into local rivers and streams or into local drinking water bores.


How can this change? In saying all this, "farmers are listening. Regenerative Agriculture is a boom industry. [...]

We don't want an end to farming, of course, we don't want to throw all the farmers out of the country, but we do want discussions about land use, what's the most suitable use of our land for food production." Mike Smith, Kaumātua & Chair, Climate ILG, Ngāpuhi, Ngāti Kahu. Episode 5 of the 100 Year Forecast, The Spinoff.


I believe we can fix the issues in Canterbury, the country, and across the world with a switch back to historic methods of food and fibre production. Once again, planting Cocksfoot and Tall Fescue - increasing the carbon content of the soil so the soil holds more water and therefore less reliance on irrigation. Call it Regenerative Agriculture if you'd like, but farming to the limits set by the landscape; calling a spade a spade, and reinstating what Canterbury is - the home of Dryland Agriculture in Aotearoa, New Zealand.


Geography, digital geography has a role to play in the various outcomes of Climate Change, watch this space as new technologies and methodologies evolve in our ever-changing world.

- Matt Couldrey [geoid - digital geography]

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