Treeline moving north: scientists

Scientists say they have evidence the tree line is moving farther north. They say they've found shrubs in arctic Alaska are growing bigger, and they're showing up in previously barren areas.

The scientists compared aerial photographs taken 50 years ago with recent pictures.

Matthew Sturm is one of the scientists who worked on the project.

He says the results are dramatic.

"So what we're seeing is individual shrubs are getting bigger and patches of shrubs that existed fifty years ago are now denser, thicker with more shrubs," he says. "In areas where there weren't any shrubs fifty years ago now have new shrubs colonized or taken over."

The findings support theories that the area is getting warmer.

The results of the study are featured in this month's edition of "Nature" magazine.