On account of the adverse effect it has on biodiversity, a 15-year moratorium on planting of pine trees has been demanded by an NGO the Dhaulandhar Education Society.Mr Ajit Kumar, an environmentalist, who head the NGO, while inter-acting with mediapersons here today said it was high time that the government imposed a minimum of 15 years' moratorium on planting of pine trees as the trees had ruined the local life support system in the villages.He added that already 60 per cent of the total forest area in Himachal was covered by pine trees.