The number of native plants under threat is being partly blamed on farm conversions from sheep to dairy.
A new study shows six species of native plant are now regarded as extinct and the number of plants under threat has jumped almost 50% to 180.
Department of Conservation scientist Peter de Lange says a change from sheep farming to dairy is having a significant effect on land, particularly in the drier eastern parts of the South Island.
He says it's draining wetlands and starving plants.
But Federated Farmers is not sure how much land the Department of Conservation needs to protect plants, noting a considerable amount is already under DOC's control.
It says the survey results are not surprising as the areas studied are heavily populated.
