Pollution is a sin, say church leaders at sea

John Paul II to join Orthodox church's 'Green Pope' at the end of his Mediterranean voyage to protect Mother Earth

Like a latter-day Noah's Ark, a nine-storey ferry is nosing its way up the Adriatic this weekend on a voyage to ecclesiastical and ecological history.

Spiritually skippered by the Eastern Orthodox "Pope" – and packed with his bishops, Roman Catholic cardinals, top scientists and environmentalists – the 34,000-tonneFestos Palace completes its pilgrimage tomorrow in Venice with an unprecedented joint initiative by the heads of the long-warring Catholic and Orthodox churches.

Pope John Paul II and Patriarch Bartholomew will together sign a declaration warning that the world faces an environmental and social crisis, asserting that Christians have a particular responsibility to combat it, welcoming the rise of environmental consciousness and laying the foundations for developing a joint "environmental ethos". Senior clerics say it is the first time that two church leaders have signed a joint declaration of action of this kind.

Originally they were to meet in the magnificent Palazzo Ducale – from which a 13th-century Doge diverted a crusade to sack Constantinople, marking the nadir of relations between the two halves of Christendom – to sign the declaration together. But due to the Pope's failing health and energy, he is now to stay in Rome, from where he will address the Patriarch's party, and simultaneously sign the declarationon television.

Today, in another unprecedented gesture of reconciliation, Patriarch Bartholomew will celebrate mass in the sixth-century Byzantine-style but Catholic Basilica of Sant' Apollinare Nuovo in Classe, near Ravenna. It is thought to be the first time that an Orthodox Patriarch has celebrated a mass in a Catholic church.

The service and the signing come at the climax of a series of floating symposia during the last seven years, the brainchild of the Patriarch, whose enthusiasm for environmental issues has led to him being dubbed the "Green Pope". He first took another ferry through the Aegean to the island of Patmos in 1995 for the 1,900th anniversary of the writing of the Book of Revelation. There the Orthodox Church formally declared pollution to be a sin. Subsequent voyages have included a circumnavigation of the Black Sea and a voyage down the Danube immediately after the Kosovo war.

For the past two years the organisers have been wondering how to involve Pope John Paul II in this crusade. The text to be signed tomorrow is being kept secret, but the Orthodox Church has been discussing whether it should include a joint declaration of the sinfulness of degrading the environment. The Patriarch starkly warned the delegates – who include Richard Chartres, the Bishop of London – that "we witness death approaching on account of trespassing against limits that God placed on our proper use of creation".

Prince Sadruddin Aga Khan warned it might too late to prevent catastrophic environmental damage.

"Environmental crises like climate change won't wait while we procrastinate for 'conclusive' scientific data," he said.

As the ferry steamed up the Adriatic, stopping in six countries from Greece to Italy, senior politicians came aboard. Albania's leaders were taken to task for failing to fence a former factory site where children play among deadly lindane and chromium. And yet the delegates also heard how the recently warring nations of the former Yugoslavia were beginning to put together joint initiatives to clean up their environment.