Scientists around the circumpolar world say lakes and ponds are changing so fast it may be impossible to reverse the trend.

Twenty-six researchers from countries including Canada, Russia and Finland have released a new study which they say gives a dramatic signal of changes happening in the Arctic.

The report's findings are based on core samples taken from lake beds in five Arctic countries.

The researchers say the mud in those lake beds is like a history book: the deeper down it goes, the older it gets. And that history book, they say, reveals how the Earth's climate has changed over hundreds of years.

John Smol of Queen's University in Kingston, Ont. says nowadays, ice is melting earlier and forming later because of climate warming.

And Smol says the that warming trend is changing the make-up of animal and plant communities in the mud.

"What we're seeing in the last hundred years or so is remarkable," he says. "It's totally out of line with any of the small natural changes that happen in ecosystems."

Another author, Alex Wolfe of the University of Alberta, conducted research for the study in Norway's High Arctic. He says climate changes are having an impact throughout the food web.

"This study in itself signals how geographically widespread these first hints of large-scale ecological change really are expressed," he says.

The study shows lakes and ponds in Nunavik and Labrador aren't warming at the same rate.

Wolfe and Smol say that's further evidence that climate, not contaminants, is the main source of changes happening in the Arctic.