Leaf peepers in Japan finding duller forests thanks to climate change

In Japan, when the autumn paints trees red and yellow and all the shades in between, crowds of locals head for the hills. The tradition, called momijigari, or red-leaf hunting, dates back to the 8th century CE, when poets described scores of people in the countryside, admiring fall’s beauty.

As climate change progresses, however, the foliage is getting duller, a new study says. Scientists recently used archival photographs to analyze the brightness of autumn leaf color across several mountain sites in Japan between 2011 and 2020, compared the results to climate data, and discovered that warmer temperatures and leaves opening earlier in spring led to less vibrant hues (Sci. Reports 2025, DOI: 10.1038/s41598-025-14547-2). This may be because longer growing seasons drain leaves of vitality and lower their levels of anthocyanin, which are flavonoid pigments that turn leaves red.

Projecting their findings into the future, the scientists warn that by the end of this century, momijigari followers may encounter autumn forests that are 15% duller than they were in the period between 1981 and 2000. Under the most severe climate scenario, annual mean temperature in Japan is forecast to rise as much as4.5 °C by the period between 2081 and 2100, according to a 2025 report by the Japan Meteorological Agency.

“I feel it’s quite sad if the autumn season and its culture is diminished in Japan,” says Dai Koide, a plant ecologist at the National Institute for Environmental Studies who led the study.

The chemistry of how leaves turn color

Across the globe, more than 1,000 species of deciduous trees and shrubs turn yellow, orange, and red in the fall.

Dropping temperatures and shortening days trigger the process, which is part of how plants conserve nutrients before the winter.

“If you knew your house was going to burn down every fall, you would probably get out your valuable stuff beforehand, and that’s kind of what plants do,” says Nicole Hughes, a biologist at High Point University who wasn’t involved in the research. “For them, the valuable stuff is nutrients: nitrogen and phosphorus.”

Much of the nitrogen is bound up in proteins that hold in place chlorophyll, the green pigment essential for photosynthesis. When these proteins break down in the fall, “chlorophyll gets broken down, too, and the green color is lost,” Hughes says.

The nutrients, meanwhile, get pulled back from leaves into branches and trunks for overwinter storage. As chlorophyll disappears, pigments such as carotenoids and xanthophylls become visible and leaves appear yellow. For European aspen, such visible yellowing happens once chlorophyll levels are down by three-quarters of their summer levels, research shows.

Waning colors are a global trend

Koide first noticed autumn colors dimming in the Japanese Alps in 2016 in what he calls a “shocking” experience that inspired him to look for the “mechanisms behind the phenomenon.”

For their study, Koide and colleagues turned to a database of digital photographs captured hourly at three alpine sites in Japan. The team then analyzed the images with the visible atmospherically resistant index (VARI), an indicator of leaf color brightness.

Their results on waning leaf color back up other modern data on climate change’s effect on leaf pigment.

A 2023 study comparing modern data with the meticulous observations of one farmer between 1883 and 1912 reports that leaves of several tree species in Ohio turn yellow and red later than they did in the past. For example, Ohio’s black oak trees now change colors 16 days later than they did a century ago.

A 2025 study in South Korea finds similar delays in Asian maple and ginkgo trees. “If it’s warmer outside in the fall, holding all else equal, trees are more likely to hold onto their leaves a little bit longer because they can take advantage of the conditions and keep photosynthesizing,” says Pamela Templer, a biologist at Boston University who wasn’t involved in the study.

Yet other research suggests that in the future, the autumn display may come earlier. A study based on European trees and published in 2020 in Science predicts that by the end of the 21st century, the aging and falling of autumn leaves could advance by 3–6 days.

In that paper, the scientists argue that with springs also starting earlier, leaves will basically run out of space to store nutrients. They’ll fall once “they’ve accumulated the maximum amount of carbon that they can for the year,” says Templer, who did not work on the Science study. The timing of warming may be what matters. In 2023, the same group of researchers showed that while warm springs made fall colors arrive earlier, warm autumns delayed the show.

But how the forests will behave in any particular year is hard to forecast, considering that a multitude of factors drive autumn colors, including temperature, drought, and the availability of nutrients such as nitrogen.

Leaf peepers need to wait for ideal conditions

The dulling of autumn reds and yellows could hamper momijigari, Koide says, as well as the local economies that depend on fall tourism in Japan and elsewhere.

Yet with further study into the phenomenon, governments could create nature preserves for autumn foliage, Koide says. Other proposed interventions, such as stockpiling snow in certain places to delay color changes, may be controversial, he says, since they boost human interference with nature.

For now, to get that perfect autumn show, leaf peepers need to wait for conditions that are just right, Templer says. That’s when “the trees are basically marching through senescence at a regular pace and not being accelerated by some external stress—whether it’s extreme drought, extreme rain, extreme fungus, extreme anything.”

It’s that gradual change that brings the most vibrant reds, for instance, Templer says, “and those are just so beautiful.”