Pope Benedict on Wednesday made another strong appeal for the protection of the environment, saying issues such as climate change had become gravely important for the entire human race.

The Pope made his appeal, his second on environmental issues in four days, at the end of his general audience before some 16,000 people in St Peter's Square.

"Care of water resources and attention to climate change are matters of grave importance for the entire human family," he said.

"Encouraged by the growing recognition of the need to preserve the environment, I invite all of you to join me in praying and working for greater respect for the wonders of God's creation," he told his listeners, speaking in English.

The Pope gave his backing to a symposium called "The Arctic: Mirror of Life," on religion, science and the environment, due to start in Greenland on Thursday and be attended by scientists and religious leaders.

Earlier this month, scientists said previously unknown islands were appearing as Arctic summer sea ice shrinks to record lows, raising questions about whether global warming was outpacing U.N. projections.

Benedict and other world religious leaders have been banging the environmental drum more loudly recently.

Last Sunday in central Italy, Benedict led the Catholic Church's first 'eco-friendly' youth rally and told up to half a million people that world leaders must make courageous decisions to save the planet "before it is too late".

Under Benedict and his predecessor John Paul, the Vatican has become progressively "green".

It has installed photovoltaic cells on buildings to produce electricity and hosted a scientific conference to discuss the ramifications of global warming and climate change, widely blamed on human use of fossil fuels.

Last month Benedict said the human race must listen to "the voice of the Earth" or risk destroying its very existence.