Tax breaks encourage more riparian planting

17:00, Jul 17 2013
Kaipara Harbour
HOTEO FLOOD: The sediment laden freshwater floats on Kaipara Harbour seawater.

Efforts to stop continued Kaipara Harbour degradation got a boost last week with government plans announced to improve water quality nationally and change the way fresh water is managed.

This includes farmers now being able to deduct riparian plantings as an operational expense.

"The key change to the Income Tax Act 2007 is that it now explicitly allows deductions for plantings to prevent or mitigate discharges into water courses or water bodies," Conservation Minister Dr Nick Smith says.

Joseph Gaffney
PLANTING DAY: Joseph Gaffney helps plant up areas of his parents’ Wayby property.

"It also extends the provision from just trees to shrubs and other plantings," Dr Smith says.

Fish & Game has often battled for freshwater habitats and says the plans will help reduce agricultural runoff.

"It's a simple, common sense approach to incentivise good environmental custodianship," Fish & Game chief executive Bryce Johnson says.


"Riparian planting has long been known as a very useful tool to mitigate the impacts of runoff," he says.

Issues concerning harbour sedimentation from surrounding farm land were highlighted in the Rodney Times last Thursday.

The huge harbour is the nursery to west coast snapper and the last on the North Island's west coast with broad seagrass meadows, used as a habitat by the young fish.

The region's hills were originally clad in dense bush, the soil tightly bound by root systems.

Sediment started moving when Maori burned bush to clear it. Massive destabilisation followed when European settlers began arriving in the 1830s and started gum digging and timber production, then cleared bush for farming.

Sedimentation rates nationally have gone from almost zero up to 5 millimetre increases annually in the same estuaries, and up to 30mm annually near large catchment outlets.

The flooding Wairoa River dumps more than 60 per cent of the sediment coming into the harbour, followed by the Kaipara/Kaukapakapa River and then the Hoteo River.

Southern seagrass meadows get silt from Hoteo River flooding.

Most of the Hoteo's sediment comes from high up in the catchment, rather than on coastal land, NIWA limnologist and environmental chemist Max Gibbs says.

"Protective forest has been removed from steeper hill sides," Mr Gibbs says.

"Cattle and sheep hooves cut up the soil. It is washed onto the lowlands by rain and into the river."

Dr Gibbs was part of a NIWA team that took core samples around the harbour. From these they could tell the rates of sedimentation, where the silt was coming from and what land activity was involved.

Suspended sediment also affects the growth of marine plants by blocking sunlight, NIWA coastal sedimentologist Andrew Swales says.

Three property owners on the Hoteo River have begun stabilising their river margins and land with riparian plantings, with Auckland Council funding help.

Max and Helen Kidd own a rolling-to-steep 109 hectare beef farm at the Hoteo River source near Te Arai. A former engineer, Mr Kidd says they originally fenced and planted up "death trap" gullies in steep areas for stock protection. The 50,000 native plantings in the wetland remnants joined two neighbouring QEII areas, making a nearly 4 kilometre bush corridor.

Further down the river at Wayby, lifestyle block owners Gaylene and Brendan Gaffney have put 850 plants along a waterway draining into the Hoteo. The river regularly floods the nearby Whangaripo Valley.

"During flooding sediment gets deposited on the flood plains," Dr Gibb says.

"Riparian planting will help stop that deposited silt from then being washed into the river in subsequent flooding. Lower areas are common for dairy farming. The hills more for dry stock and sheep."

Closer to the river mouth in the Kaipara Hills, Stephen Dill has already fenced and planted up 300 metres of riverside on his steep 500ha sheep and beef farm, with plans for more.

He says he has paid half of the $20,000 fencing and planting bill so far, the Auckland Council paying the rest.

Kaipara Flats School pupils have planted up 700 trees on other steep slopes on the farm as part of Trees For Survival, he says.

A duck shooter and whitebaiter, Mr Dill wants to give the ducks somewhere safe to nest, and provide shading and vegetation for whitebait species which lay their eggs in long grass beside waterways, close to the sea. Four of the five whitebait species are listed as threatened.

With 2 kilometres of river boundary, tax relief may help Mr Dill with more planting.

"I'd like to fence off more but financially the reality of cattle and sheep farming at the moment means that's unrealistic," he says.

More flooding is expected as the atmosphere warms, along with rising sea levels bringing more saline water to flood plains, collapsing banks and releasing silt.

Two public workshops covering Auckland Council funding are on July 25 at the Warkworth Masonic Hall, 3 Baxter St, and August 1 at the Helensville War Memorial Hall, both 7pm-9pm.

Rodney Times