Emperor Naruhito and Empress Masako made an online appearance at a tree-planting festival in Shimane Prefecture, western Japan, on Sunday.
This year's event was held in the city of Oda. It had been postponed by one year because of the coronavirus pandemic.
The Emperor and Empress made an online appearance from the Akasaka Imperial Residence in Tokyo.
Speaking via video link, the Emperor said forests have provided people with lumber, water and other resources, as well as soil to nurture a comfortable environment and culture.
He said forests also play an important role in the conservation of the Earth's environment by helping to prevent climate change.
The Emperor expressed hope that the sustainable green eco-system, which involves humans and forests, will be conveyed from Shimane to the entire country, and to the future.
The Emperor and Empress planted cedar, rhododendron and other saplings in large wooden planters. The saplings will be sent to Oda to be grown there.
The Imperial couple also attend a national sports festival and other events each year. This was the first time they have remotely attended a ceremony.