Federal researchers are using satellite photos of a national park in the western Arctic to show how climate change is prompting vegetation from southern Canada to creep into the tundra, possibly threatening the northern ecosystem.

As part of International Polar Year research, Ian Olthof and his team at the National Research Council in Ottawa are poring over thousands of satellite photos of Ivvavik National Park, which straddles the tree line west of Aklavik, N.W.T.

The satellite images are being compared to similar photographs taken of the park 20 years ago in order to see how vegetation normally found in southern climates is slowly invading the tundra.

"What we're primarily seeing is that there is an increase in vegetation in northern Canada," Olthof, who is with the council's Canada Centre for Remote Sensing, told CBC News in an interview.

"Areas that were normally occupied by herbs, for example, are becoming occupied by shrubs. We're seeing a migration of the tree line northwards. These sorts of changes have implications on wildlife and the people who depend on wildlife in the North."

Olthof said his team also expects to see shrubs and herbs displacing non-vascular plants, such as lichens and mosses, that have long existed on the tundra.

The researchers paid a visit to the park itself last month for a closer view of the plants that are there.

They will feed all the satellite images into a computer, then spend this winter analyzing the data. They hope to have some preliminary results within a year.

He warned that the migration of trees and plants such as willows and alders could have a disastrous effect on northern animals such as caribou.

"If the tundra disappears, then these wildlife populations will disappear as well, and the whole way of life that goes along with it," he said.