WASHINGTON — The capital's famous cherry trees are primed to burst out in a perfect pink peak about the end of this month. Thirty years ago, the trees usually waited to bloom till around April 5.

In central California, the first of the field skipper sachem, a drab little butterfly, was fluttering about on March 12. Just 25 years ago, that creature predictably emerged there anywhere from mid-April to mid-May.

And sneezes are coming earlier in Philadelphia. On March 9, when allergist Dr. Donald Dvorin set up his monitor, maple pollen was already heavy in the air. Less than two decades ago, that pollen couldn't be measured until late April.

Pollen is bursting. Critters are stirring. Buds are swelling. Biologists are worrying.

"The alarm clock that all the plants and animals are listening to is running too fast," Stanford University biologist Terry Root said.

Blame global warming.

The fingerprints of man-made climate change are evident in seasonal timing changes for thousands of species on Earth, according to dozens of studies and last year's authoritative report by the Nobel Prize-winning international climate scientists. More than 30 scientists told The Associated Press how global warming is affecting plants and animals at springtime across the country, in nearly every state.

What's happening is so noticeable that scientists can track it from space. Satellites measuring when land turns green found that spring "green-up" is arriving eight hours earlier every year on average since 1982 north of the Mason-Dixon line. In much of Florida and southern Texas and Louisiana, the satellites show spring coming a tad later, and bizarrely, in a complicated way, global warming can explain that, too, the scientists said.

Biological timing is called phenology. Biological spring, which this year began today, is based on the tilt of the Earth as it circles the sun. The federal government and some university scientists are so alarmed by the changes that last fall they created a National Phenology Network at the U.S. Geological Survey to monitor these changes.

The idea, said biologist and network director Jake Weltzin, is "to better understand the changes, and more important what do they mean? How does it affect humankind?"

There are winners, losers and lots of unknowns when global warming messes with natural timing. People may appreciate the smaller heating bills from shorter winters, the longer growing season and maybe even better-tasting wines from some early grape harvests. But biologists also foresee big problems.

The changes could push some species to extinction.

That's because certain plants and animals are dependent on each other for food and shelter. If the plants bloom or bear fruit before animals return or surface from hibernation, the critters could starve. Also, plants that bud too early can still be whacked by a late freeze.