Venice (AFP) - Nobody is ever going to call Paul Schrader's "First Reformed" a feel-good movie, and the legendary screenwriter and director is fine with that.

"If you are hopeful about humanity and the planet you are not paying attention," Schrader said Thursday as he presented his latest writing and directing project at the Venice film festival.

The film turns around the uncheery theme of impending environmental apocalypse and the question of whether Christians could or should have done more to prevent it.

"I don't see humanity outliving the century," Schrader told reporters after the drama, which stars Ethan Hawke, as an unexpectedly middle-aged troubled pastor, and Amanda Seyfried, was unveiled.

The dark tale is being tipped as an outside shot for the Golden Lion, the top prize at the world's oldest cinema festival.

Outlining the thinking that lay behind his script, Schrader added: "I have to be honest. I have lived in the magic cone of history, the baby boomer years."

"A life of affluence, a life of leisure, a life of little pestilence, little war. And for that my generation has pretty well screwed the planet for our kids."

Such themes are being increasingly reflected by filmmakers: planetary destruction driven by climate warming was a prominent theme in Venice's opening film "Downsizing".

But Schrader says his tale of a former army chaplain undergoing a spiritual crisis as he grapples simultaneously with the grief of losing a son and possibly fatal illness is rooted in more than the contemporary, gloomy zeitgeist.

- Whisky secrets -

Having had a famously restrictive Calvinist upbringing, the 71-year-old said he had nurtured the idea of making a film about spiritual issues since the early 1970s, when he was breaking into the big time as the writer of Martin Scorsese's groundbreaking "Taxi Driver."

"I was just too excited by the violence, the intimacy, the sexuality of cinema to work with that more austere toolkit," Schrader said. "But a couple of years ago I realised it was time to come back to it."

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Similarly, Hawke said he had been waiting a long time for a role he described as having much resonance with his own, religion-infused upbringing.

"When I was born my great-grandmother had a clear sense I was going to be a priest and told everyone I should pay attention to the calling, if it ever came," he said.

"So I used to pray the calling wouldn't come and thank God it didn't. But I have been surrounded by religion my whole life and it has been a very important dialogue in my head.

"So it was a character I feel as if I have been waiting a long time to be offered. I put quite a lot of myself into it."

From a family of military chaplains, Hawke's character, the Reverend Toller, looks after a historic but thinly attended Dutch Reformed church in upstate New York.

It emerges that Toller is haunted by the death, in Iraq, of the son he persuaded to enlist and that he is using whisky to self-medicate for what appear to be symptoms of an ominous form of cancer.

- 'Atonement by blood' -

Tragedy recurs after the pastor begins counselling a depressed environmentalist activist, at the request of his pregnant wife, Mary (Seyfried).

This proves to be a catalyst for a spiritual rebirth of sorts, Toller rediscovering his faith in righteous anger over his discovery that the church is being bankrolled by a polluting industrialist.

Will he channel that anger into violence or find salvation in this life through resolution of a developing intimacy with Seyfried's character? Does he give in to despair or embrace hope, as represented by love?

Schrader leaves the questions unanswered with an ambiguous finale, but makes no excuse for portraying a Christian minister as a potential suicide bomber.

"Deep-rooted in Christianity there is a notion of atonement by blood," he said. "It begins with sacrifices of animals in the Old Testament and continues with the symbolic sacrifice of Christ."

"Whether you are protestant or catholic you are raised with the idea that through blood you can become clean. This is a pretty dangerous idea when you think about it but it is part and parcel of the programming we receive as Christians."