Ma has been criticized by many environmental groups. His mayoral construction of the Maokong Gondola was criticized by the Taiwan Environmental Information Center. The construction of the Taipei Arena also drew negative reactions from these groups. The Society of Wilderness (SOW; 荒野保護協會) pointed out that of the three hundred and eighty-four trees that were moved for the construction, more than a hundred had already died. The city government said that the ages of the trees are unknown; therefore, they are not protected by law. The SOW then responded that, according to pictures taken by the United States Air Force in 1947 and 1948, these trees were present already during the Japanese rule era.