Climate change is delaying peak fall foliage. Here's what to expect this year

"It's officially fall in the Northern Hemisphere, which means bright, beautiful foliage isn't far behind. Parts of the U.S. will soon start to see if they haven't already leaves and shrubs trade their green hues for vibrant shades of orange, yellow and red as the days get shorter and temperatures get chillier. "It's a really cool process that we get to watch, that trees are preparing for winter," says Alexandra Kosiba, extension assistant professor of forestry at the University of Vermont."

"As temperatures drop, chlorophyll the pigment that makes leaves appear green starts breaking down, revealing the yellows and oranges they've had all along. Leaves typically start to change color in the northernmost states by mid-September, peaking around the end of the month and later farther south. This year, Almanac predicts that leaves in northern areas of the West and Midwest will peak by Oct. 4, while much of New England and the Pacific Northwest will be at or near peak fall color by Oct. 11."

Bright foliage appears in fall when leaves and shrubs shift from green to orange, yellow, and red as days shorten and temperatures cool. Trees shed leaves to store and recycle valuable nutrients in trunks and branches before winter ice and snow can damage them. Chlorophyll, the pigment that makes leaves green, breaks down and reveals underlying yellow and orange pigments. Leaf color change typically begins earlier in northern states and later farther south. Predictive maps estimate peak dates, but timing varies with temperature, elevation, rainfall, pests, and other local factors, making exact predictions uncertain.

Read at www.npr.org