Stonyfield Farm Inc., a New Hampshire-based yogurt company, is launching a new national print ad campaign that aims to promote environmental and social causes as well as its own cultured dairy products. Gary Hirschberg, president and chief executive of Stonyfield Farm, calls the campaign concept “ad-tivism,” a combination of advertising and activism. The new ads feature well-known personalities like filmmaker and historian Ken Burns and highlight causes that matter to them, from rainforest protection to organic gardening. Stonyfield Farm hopes the do-gooder messages will attract do-gooder customers. The company has also tried to lure activist-minded buyers with messages on its yogurt lids calling for action on environmental and other issues, and by giving 10 percent of profits to organizations like the Jane Goodall Institute, which promotes wildlife conservation and research.