The future of fall: The science behind autumn color and implications of climate change

Fall Colors
The greens of conifers and a few deciduous trees that have yet to turn color contrast with the leaves of those that have at Willow State Park, Hudson, Wis., in this drone photo taken Sept. 17, 2019. Sally Shepherd / RiverTown Multimedia

Now that kids are back in school, the sun is setting before 8 p.m. and nights require more than a sheet to keep warm, thoughts are beginning to turn to the much-loved season of fall. In Minnesota and Wisconsin, autumn means pumpkin patches, apple cider and, of course, the changing of leaf colors.

According to Explore Minnesota, there are numerous factors that tell trees that it is time to begin to turn and eventually drop leaves. These include:

  • Decreasing daylight

  • The beginning of long, cool nights

  • Moist soil

Years that are wetter than average (this year, for example, was one of the wettest on record) usually result in brighter, more vibrant colors.

Autumn is also a good time to check to see if trees are healthy. According to Davey Proven Solutions for a Growing World, an organization that has a focus on trees, “early fall color can be a sign of tree stress.”

Davey suggests four steps for keeping trees healthy:

  • Hydrate the area under the tree’s branches.

  • Put a long screwdriver into the ground. If the ground is hard, the tree needs more water.

  • Add 2 to 3 inches of mulch around the tree to reduce moisture loss and maintain soil temperature.

  • Fertilize as needed.

While these steps help individual trees, it should be noted that scientists believe that as the climate continues to change, autumn colors and patterns through out the region and country will also change.

Yingying Xie wrote an article for Yale Climate Connections. In it she writes:

“Global warming is bringing changes to the region’s fall colors. In general, warmer temperatures cause leaves to turn color later in the season.”

Climate changes can result in shorter color seasons and less predictable color peaks.

In an article on PBS’s website, Susan M. Brackney echoes Xie’s claims. Brackney writes:

“Cool temperatures and moist soil are optimal for the most spectacular displays of fall color. However, with the earth’s rising temperatures and more extreme weather events, autumn might not look or feel quite like it has in the past.”

While fall colors may become more unpredictable in the future, Minnesota and Wisconsin organizations have tools in place to try and help tourists find the optimal time to see fall colors.

Explore Minnesota’s website includes a chart of regions in the state and the percentage of trees that are at peak color. For the region around Red Wing and Pierce County, the peak colors usually appear in late September to early October.

For more information about local color changes and the impact of climate, visit

You can find Wisconsin's full fall color report at Videos show brilliant colors at such spots at Tim's Hill in Price County.

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