Perhaps emboldened by the " Live Earth " benefit concerts and Al Gore 's Nobel Peace Prize , this is the family member who is the first to point out , over the bountiful Christmas dinner , that the 2.6 billion holiday cards sold each year in the United States could fill a landfill the size of a football field 10 stories high , or that those conventional lights on the Christmas tree contribute up to nine times as much greenhouse-gas emissions as the leaner-burning L.E.D. models ; or that some Christmas-tree growers use as many as 40 different pesticides , as well as chemical colorants , on their crops .