Pope Benedict, leading the Catholic Church's first 'eco-friendly' youth rally, on Sunday told up to half a million people that world leaders must make courageous decisions to save the planet "before it is too late".
"A decisive 'yes' is needed in decisions to safeguard creation as well as a strong commitment to reverse tendencies that risk leading to irreversible situations of degradation," the 80-year-old Pope said.
Wearing green vestments, he spoke to a crowd of mostly young people sprawled over a hillside near the Adriatic city of Loreto on the day Italy's Catholic Church marks it annual Save Creation Day.
More than 300,000 people had slept on blankets and in tents or prayed during the night. Organisers said they were joined by some 200,000 more who arrived from throughout Italy on Sunday.
"New generations will be entrusted with the future of the planet, which bears clear signs of a type of development that has not always protected nature's delicate equilibriums," the Pope said, speaking from a white stage.
In one of his strongest environmental appeals, Benedict said: "Courageous choices that can re-create a strong alliance between man and earth must be made before it is too late." The Pope closed the rally with a Sunday morning mass.