Some tour companies advertise jungle treks, scuba diving, and other ___ as “nature tourism”.

expeditions 意為「探險、遠征、考察」。與前文的叢林健行 (jungle treks)、水肺潛水 (scuba diving) 同屬戶外探索活動，完美契合「自然旅遊 (nature tourism)」的語境。