One alternative for sheep and beef farmers could be growing trees to gain carbon credits.
Stored carbon is worth $21 a tonne now, Woodnet consultant Margaret Willis said.
To enter the Emissions Trading Scheme land must not have been "forest" on January 1, 1990. The definition of forest is potential 30 per cent canopy cover by trees that have the potential to reach 5m - and that includes mānuka.
It's important to know the history of land, Willis said, because farmers clearing land forested before that date could face a penalty of $50,000 per hectare.
On the plus side, farmers can boost their poplar pole and riparian plantings to get them to "forest" level, then register them in the scheme. For poplars that means choosing wide canopy species and planting them no more than 20m apart - for some the addition of just a few poles can make an erosion planting a "forest".
Farmers can also go into forestry partnerships with Government, in its One Billion Trees programme. If the planting isn't done New Zealand will face "a massive international bill in the billions", Willis said.
People were clearly already considering planting trees for carbon, and asked plenty of questions.
Horizons Regional Council environmental co-ordinator Dave Harrison went on to talk about trees in the council's Sustainable Land Use Initiative (SLUI), which aims to keep soil on the hills so that farmers can keep using it.
His council is "awash with money" for new planting, but under SLUI farmers have to put in about half the cost of the work. It's important for them to have skin in the game, he said.
Farmers also heard from Beef + Lamb NZ and a Whanganui vet, then had a panel discussion.