Global warming is having a widespread, systematic effect on hundreds of plant and animal species, two new studies say, from hastening annual flower blooms to forcing butterflies farther north.

Nature’s springtime rituals — such as egg laying and emerging from hibernation — are occurring days earlier than usual for many temperate zone species because of the increasing temperatures during the last two decades, according to Thursday’s issue of the journal Nature.

The studies, which reviewed existing research primarily in Europe and North America, also confirmed that a variety of species, including butterflies and marine invertebrates, have shifted their range edges northward about 3.8 miles per decade as temperatures have crept up. Even when habitat destruction or other possible causes for behavior changes were considered in one study, extensive statistical analysis still pointed to global warming as the reason for the changes.

The most dramatic effects might be decades away, as rapidly rising global temperatures combine with other environmental stresses such as habitat destruction and invasive species, the authors said.

“Many biologists, myself included, believe we’re standing at the edge of a mass extinction,” said Terry Root, a senior fellow with the Institute for International Studies at Stanford University. “A lot of species aren’t going to make it because they have to change and move (to new locations) so rapidly. And how can they do that when their habitat has been destroyed?”

The studies did not examine many other parts of the world. The species studied represent only a small fraction of the globe’s flora and fauna, and not all species studied showed effects.

But together the new studies suggest that change is under way in many ecosystems, further fueling a debate that has raged for more than a decade about man’s influence on the climate.

The Earth’s surface temperature has risen by about 1 degree Fahrenheit in the last century.

Some scientists have predicted average global temperatures could rise up to 10 degrees Fahrenheit in the next century. But others say global warming is simply part of the natural cycle of the planet, and plants and animals will adapt as always.

But the researchers believe unpleasant surprises could be on the horizon, as warming combines with other human activity.

“Some say, ‘Who cares if a flower is blooming earlier or the range is shifting north?”‘ said biologist Camille Parmesan of the University of Texas at Austin, who co-authored one of the Nature articles. “The idea that everything can shift around the globe (in response) is fine if everything is a wilderness area. The problem is, a lot of the world is a cornfield or urban area like Chicago.”