Horizons Regional Council may accelerate work to protect erosion-prone land in reaction to climate change, environmental manager Craig Mitchell says.
Continued at its present rate, the council's Sustainable Land Use Initiative will have reduced erosion by 27 per cent in 2043. But under major climate change, the reduction could be a mere five per cent, research shows.
The initiative makes changes to 3500ha of land a year, and has reduced silt entering the region's waterways by 9 per cent.
The council could accelerate erosion protection, Mr Mitchell said.
It has already agreed to charge ratepayers an extra $2 a year for it for the next two years, an incremental increase.
It could also further prioritise the catchments where most sediment comes from - though Mr Mitchell said the initiative was voluntary, so there was a limit to the pressure that could be applied.
"We like to prompt them along. We are doing pretty well in the voluntary space."
And it could alter the thrust of the initiative more towards planting trees - either to forestry, to ceasing to spray scrub and grazing only with sheep, or to complete retirement, possibly with the planting of natives.
The Government's reduced and revived Afforestation Grant Scheme subsidises new planting.
There were applications for 9000ha nationwide to be planted next season, much of it in manuka.
There will be 1091ha planted in the Horizons region under the scheme, about a sixth of the total approved.
In another post-flood anti-erosion move, the council has decided to give away poplar poles to landowners in the worst affected parts of the region for the next two years. Mr Mitchell said up to 10,000 could be given.
The worst affected areas are in the lower and middle Whanganui, Whangaehu, Turakina, Whenuakura and Waitotara river valleys. Most of the slips were only 1m-2m deep, and on north facing slopes of 20 to 35 degrees.
Slips are 90 per cent less likely on slopes covered with a canopy of trees.
"All the forestry we are directly involved with has held together very, very well. The only damage is to tracking and infrastructure," Mr Mitchell said.
Pine forest soils will slip under heavy rain after harvest and before the next crop takes hold. The stumps and roots rot out in 18 months, and the next rotation of trees, if planted immediately, start to hold the soil in five years.
In June, harvested forest sustained a bit of damage, but not as much as slopes in pasture. Slash from logged forests was swept downhill and on to flat farmland, especially in the Whangaehu Valley, and there were some slips.
"Pinus radiata isn't the answer in all situations. Native planting for bees and managed retirement can have a big impact on reducing the sediment," Mr Mitchell said.