TORONTO (AFP) - The race for the Oscars heats up this week at the Toronto International Film Festival, where a raft of movies will focus on survival in dark times, with mounting political, religious and racial tensions around the world.

More than 300 feature and short films from 74 countries will be screened at the biggest film fest in North America, which opens on Thursday and runs through Sept 17.

The event is often seen as a way for Oscar-conscious studios to generate buzz about their movies. "This year's big theme is survival," festival chief executive Piers Handling said.

From climate change and overpopulation to terrorism, North Korea and fringe right-wing groups in America, people are facing "an atmosphere of great uncertainty and a real fear about certain issues".

"Some of the films are absolutely uplifting, showing that individually or collectively (you can overcome) if you harness your resources and work together," he added.

He highlighted The Mountain Between Us, starring Idris Elba and Kate Winslet as two strangers fighting to stay alive after a plane crash in the wilderness, and Stronger, about the 2013 Boston Marathon attack and starring Jake Gyllenhaal, as examples of films showing individuals trying to survive.

By contrast, American director Alexander Payne offers a quirky solution to the issue of human consumption exhausting Earth's resources. His social satire Downsizing, about a man who chooses to shrink himself to simplify his life, stars Matt Damon.

Other featured films chronicle efforts to live on in times of war and chaos.

Among those expected to generate buzz are the Winston Churchill biopic Darkest Hour, starring Gary Oldman; Angelina Jolie's Cambodian genocide drama First They Killed My Father; and Kings, based on the 1992 Los Angeles race riots, starring Daniel Craig and Halle Berry.