The Earth's forests, deserts, landscapes and vital ecosystems risk a "major transformation" in the next century due to climate change, international scientists warned.

Some of these changes are already under way in the southwestern United States, where massive wildfires are destroying pine forests and transforming swaths of territory into shrubland.

In the next 100-150 years, these changes will likely extend to savannas, deserts, and woodlands, upsetting ecosystems and imperiling plant and animal life, particularly in areas like Europe and the United States, researchers warned in the journal Science.

"If we allow climate change to go unchecked, the vegetation of this planet is going to look completely different than it does today, and that means a huge risk to the diversity of the planet," said co-author Jonathan Overpeck, dean of the School for Environment and Sustainability at the University of Michigan.

The report is based on fossil and temperature records from a period that began 21,000 years ago, when the last Ice Age ended and the planet warmed seven to 13 degrees Fahrenheit (4-7 degrees Celsius).

But experts say their predictions are conservative, since this historical warming, caused by natural variabilit

y, took place over a much longer period -- from the Last Glacial Maximum 21,000 years ago until the early Holocene, about 10,000 years ago.

But human-caused climate change is different. The burning of fossil fuels like oil and coal emits heat

-trapping gases around the planet. The Earth is currently heating up at much quicker pace.

"We're talking about the same amount of change in 10-to-20 thousand years that's going to be crammed 

into a century or two," said Stephen Jackson, director of the US Geological Survey's Southwest Climate Adaptation Center. 

Researchers described their work as the most comprehensive s

tudy to date, based on pollen and plant-fossil records from 594 sites worldwide, dating back to 

between 21,000 and 14,000 years ago.

Every continent except Antarctica was included.

The most significant changes were seen in the mid-to-high latitudes of North America, Europe and southern South America. AFP