Pope Benedict called on Thursday for the earth to be protected for future generations, saying the world had been "scarred" with erosion and deforestation and its oceans squandered to fuel an insatiable consumption.
Addressing some 150,000 young Catholic pilgrims in Sydney, the pope said some had come from island homes whose very existence was threatened by rising sea levels and others from drought-hit nations such as Australia.
The pontiff told the World Youth Day gathering on the shores of Sydney Harbour that protecting the environment was "of vital importance to humanity".
On his flight from Rome to Sydney, the pope said he witnessed the sparkle of the Mediterranean, the grandeur of the north Africa desert, the lushness of Asia's forests and the vastness of the Pacific Ocean.
"It is as though one catches glimpses of the Genesis creation story -- light and darkness, the sun and the moon, the waters, the earth and living creatures," he said.
"Reluctantly we come to acknowledge that there are also scars which mark the surface of our earth, erosion, deforestation, the squandering of the world's mineral and ocean resources in order to fuel an insatiable consumption."
In an earlier welcoming speech to Australian Prime Minister Kevin Rudd, the pope said: "It is appropriate to reflect upon the kind of world we are handing on to future generations".
He said there was a "need to protect the environment and to exercise responsible stewardship of the goods of the earth".
The pope said Australia was "making a serious commitment" to saving the environment. The Rudd government is in the throws of preparing a carbon trading system aimed at cutting greenhouse gases by 60 percent of 2000 levels by 2050.
Australia, one of the world's highest per capita greenhouse emitters due to coal-fired power stations, is in the grip of the worst drought in 100 years and is struggling to save its major river system that feeds the nation's food belt.
POPE THANKS ABORIGINES
The pope also praised Australia for apologising for past injustices to Aborigines, saying it was a courageous move to repair race relations and offered hope to the rest of the world.
Rudd officially apologised to Aborigines in February.
Australia's 460,000 Aborigines make up about 2 percent of the country's 21 million population and have consistently higher rates of unemployment, substance abuse and domestic violence, as well as a life expectancy 17 years less than other Australians.
The pope thanked Aborigines for a traditional welcoming ceremony on Thursday, before he sailed up Sydney Harbour to greet World Youth Day pilgrims and, as is the tradition in Australia, acknowledged Aborigines are the first people of Australia.
"I am deeply moved to stand on your land, knowing the suffering and injustices it has borne, but aware too of the healing and hope that now at work...," he said.
The Catholic Church hopes World Youth Day, the brainchild of the late Pope John Paul II, will revitalise the world's young Catholics at a time when the cult of the individual and consumerism has become big distractions in their daily lives.
The pope said the "social world" also had scars, highlighting alcohol and drug abuse, violence and sexual degradation. He questioned how the media's portrayal of violence and sexual exploitation can be considered "entertainment".
He warned young pilgrims "do not be fooled by those who see you as just another consumer".
The pope has said he will apologise to Australian victims of sexual abuse in the church during his visit. Broken Rites, which represents abuse victims, has a list of 107 convictions for church abuse, but says there may be thousands more victims.
The pope confronted the issue of sexual abuse in the church during a visit to Washington in April, meeting victims and vowing to keep paedophiles out of the priesthood.
Some sex abuse victims plan to protest against the papal visit in Sydney, along with a group called "No Pope" which opposes church teachings on sex, marriage and abortion.
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