How El Niño Could Affect Fall Colors in the Great Lakes Region

By KYRMYZY TUREBAYEVA

Capital News Service

LANSING – This year, El Niño could delay fall color in the Great Lakes region, make the colors less vibrant in some areas or shorten the period of peak fall color.

However, scientists note that local weather, precipitation, the conditions in which trees grow and many other factors also influence the timing and intensity of fall color.

El Niño is a climate phenomenon associated with the periodic warming of surface waters in the Pacific Ocean.

It influences atmospheric circulation and may contribute to a warmer fall in some parts of the Great Lakes region this year.

Experts at The Morton Arboretum in Illinois say that warming associated with El Niño could lead to later fall color in the Chicago area and shorten the period of the most vibrant colors.

However, El Niño is not the only factor that determines when leaves change color.

In Michigan, fall color is developing roughly on its usual schedule this year, according to Bert Cregg, a professor of horticulture and forestry at Michigan State University.

“The timing of fall color varies considerably across the state depending on where the trees are located,” Cregg said. 

“The season typically begins in the western Upper Peninsula in late September and reaches southeastern Michigan by late October,” he said. “As a result, the period between the beginning of fall color in different parts of the state can span five to six weeks.” 

Tree species also play an important role.

According to Cregg, maples, aspens and poplars are usually among the first trees to change color.

Oaks change color later and generally produce less vibrant shades.

Across much of Michigan, maples provide the most striking reds, oranges and yellows.

Peak color in maples typically lasts about one and a half to two weeks.

Christy Rollinson, a senior scientist in forest ecology at the Morton Arboretum, said, “We saw a lot of weather extremes this summer, from drought to heavy rainfall, which will likely impact trees and their foliage very differently and have isolated effects.” 

According to Rollinson, drought typically contributes to earlier fall color, while a warm fall associated with El Niño may lead to later color change. 

These factors can work in opposite directions, so the outcome depends on local conditions.

Day length, nighttime temperatures and local conditions also influence the timing of fall color.

“Every tree responds differently to climate change,” Rollinson said. “We are trying to understand which trees respond primarily to shortening day length and which actually need lower temperatures as a signal to begin changing color.”

“But there are other factors,” she said. “In some years, even when weather conditions are otherwise favorable, a sudden windstorm can strip trees of their most beautiful fall foliage. That is why there is no typical duration for the fall color season.”

She also noted that local environmental conditions can be just as important as weather.

Trees experiencing stress or receiving more sunlight tend to begin changing color earlier.

“A warm fall is indeed associated with later fall color, which is a consistent pattern we observe,” Rollinson said. “However, it is difficult to determine exactly how much of an effect warm fall temperatures have, because many factors influence the timing of fall color.” 

In Minnesota, differences in fall color timing can be noticeable even over relatively short distances, experts note.

“In some areas of northeastern Minnesota, peak fall color occurs in early October,” said Jessica Savage, a biologist and associate professor at the University of Minnesota Duluth. “Some plants begin changing color in September, but most reach their peak later. Cool evenings and adequate autumn rainfall generally contribute to vibrant fall colors. If nights remain warm or drought continues, red hues may be less pronounced.” 

According to Savage, Lake Superior also has an additional influence. It affects local temperature conditions, so the timing of fall color along the shoreline can differ substantially from that farther inland.

“Peak fall color along the lake and just about 20 miles inland can occur about two weeks apart,” Savage said. “Even under similar overall climatic conditions, temperature, precipitation, proximity to the lakes and local landscape features can produce different results.”

Kyrmyzy Turebayeva writes for Great Lakes Echo.