In this study, the author developed and applied a program for forest environmental education related to the unit “ecosystem” in the general science curriculum of an upper secondary school. It contained both classes to study the forest ecosystem and field studies utilizing the forest environment of Shiretoko Peninsula , which is registered as a World Heritage Site. From the results of examining students’ consciousness, the activities of the program contributed to understanding the value of biodiversity, increasing interests about forests and forest preservation, changing students’ consciousness about the value of nature and forming intergeneration ethics. Furthermore, detailed survey of students’ consciousness revealed the following: 1) Direct contact with rich forest environment urged changes in students’ value of nature from anthropocentrism to non-anthropocentrism ; 2) Experiencing forest conservation activities and studies on history about forest conservation activities in the past fostered intergeneration ethics; and 3) Cooperation with some experts engaging forest management functioned to change students’ environmental ethics in general.