Official source · Urban Farm DB

国土交通省「東京ドーム５個分の屋上緑化が創出されました！ －平成29年全国屋上・壁面緑化施工実績調査結果とりまとめ－」

This source is cited by the column “The rooftops nobody counts — what Japan's green-roof statistics do not measure.” This page records the connection before you continue to the external source.