WELLINGTON, New Zealand (AFP) — New Zealand sheep farmers are fighting to stop the loss of pasture to fast-spreading pine plantations, which earn government subsidies to soak up carbon emissions.

Concern over the scale of the farm-to-forest switch led the government to impose a moratorium in December on any new conversions not already in the pipeline.

But farmers say forestry companies are flouting the clampdown.

Last month, farmers launched a "Save our Sheep" campaign to reverse the loss of productive farmland.

Sheep numbers have plummeted to around 23 million, down from a peak of around 70 million in the 1980s, according to official figures.

Falling wool prices and rising milk and beef costs initially drove the decline, but the emissions trading since 2008 has added to the strain.

The government is now investigating potential breaches of its moratorium by forestry companies, which have been buying up farmland as recently as June.

Federated Farmers — a lobby group for rural communities — submitted to the government "a list of properties we believe have been sold for carbon forestry" since the halt, a spokesperson said.

The federation is concerned about the sale of more than 15,200 hectares of farmland, he told Agence France-Presse.

Dean Rabbidge, who runs a farm outside the Southland town of Wyndham, said some of the newly purchased farms had already been planted with pine trees.