"The tree line has moved by up to 200 metres (656 feet) in some places. Trees have not grown at such high levels for around 7,000 years," Leif Kullman, a professor at Umeaa University's department of ecology and environmental science, told AFP.

The tree line represents a limit in mountainous, northern and southern latitudes beyond which trees do not grow.

"Recordings began in 1915 but the trend has intensified in the past 15 to 20 years," Kullman said.

Sweden's climate in the past 20 years was as mild as it had been some 7,000 years ago, he added.

While some of the change could be explained by natural phenomena such as the reduction in global volcanic activity -- allowing more sunlight to warm the Earth -- the trend was clearly provoked for the most part by man-made factors.

"We can say that 75 percent of the change is due to the emergence of greenhouse gases," Kullman said.

As the climate has become milder other plants and animals have ventured further north from their traditional habitat.

"The number of plants and animals in Swedish forests has grown 100 percent in the last 50 years," Kullman said.

All rights reserved. � 2005 Agence France-Presse. Sections of the information displayed on this page (dispatches, photographs, logos) are protected by intellectual property rights owned by Agence France-Presse. As a consequence, you may not copy, reproduce, modify, transmit, publish, display or in any way commercially exploit any of the content of this section without the prior written consent of Agence France-Presse.