STOCKHOLM – Swedish teenage environmental activist Greta Thunberg will appear on a postal stamp that will be issued Thursday in her native Sweden and is part of a series focusing on the environment.The motives on the stamps “should reflect our time, where the environmental issue has been relevant and present for many years, not least through Greta Thunberg’s strong voice," Sweden’s postal company Postnord said in a statement.One with Thunberg in her trademark yellow raincoat with her braid blowing in the wind and standing atop a hill, is part of a five-stamp series themed “Valuable Nature.” They cost 12 kronor ($1.40) each, are available as of Jan.