The Earth
No, autumn leaves are not changing color later because of climate change
“Have scientists observed any changes in the timing or intensity of leaf color changes?”
Last Updated on May 21, 2024 by Daily News Staff
Fall foliage on the Danforth Campus of Washington University in St. Louis.
It’s that time of year again. The days are getting shorter, and the nights are cooling down. But when will the natural fireworks display of autumn leaves actually begin this year?
Many people believe that climate change is pushing back the start of fall leaf color to later in the year. The general thinking is that the warmer conditions anticipated under climate change will mean that trees can “hang on” to their green, energy-producing leaves longer. But scientists do not actually see this happening across North American forests, according to an expert at Washington University in St. Louis.
“Warmer temperatures in September and October reduce anthocyanin production in leaves, which could mean that fall colors would become less brilliantly red or purple,” said Susanne S. Renner, honorary professor of biology in Arts & Sciences. “This effect is well documented in certain species, such as sugar maple, where experimental cooling of branches increases anthocyanin concentration and color brilliance. If the first frost comes later than it used to, the brilliant foliage will appear later than it used to.
“However, other factors counteract this. Most important is that trees drop their leaves earlier if they have had a very productive spring and summer. This overrides any delaying effects of a warm fall.
“The end result is that leaves still start to die after about the same amount of time on the tree as they have in years and even decades past,” she said.
In fact, under some scenarios we might even see leaves turning red and yellow earlier. Renner co-authored a 2020 study in the journal Science that showed that increased growing-season productivity drives earlier autumn leaf senescence — the process through which plants break down and reabsorb key nutrients that had been deployed in leaves — in temperate trees.
“If climate warming continues unabated, the situation is likely to change after about 2040, with senescence then starting earlier than it does now,” Renner said.
Here, Renner answers a few additional questions related to autumn leaf color change.
How do temperature and moisture conditions affect leaf color?
Yellow color in fall leaves is due to the retention of carotenoid pigments (xanthophylls) in senescing chloroplasts. Red and purplish color is due to the accumulation of anthocyanins in vacuoles, starting around September.
Rain does not affect these basic processes. Cold temperatures, however, enhance anthocyanin production, as shown experimentally in sugar maple. One can observe this in the sugar maple trees along St. Louis streets, which start turning colors at the very top, where the microclimate is coldest.
How might climate change alter color dynamics?
Because climate warming has resulted in warmer falls, in Canada and North America we are seeing less brilliant fall colors. Color brilliance is hard to quantify, but the effect has been experimentally demonstrated in sugar maple trees.
An interesting confounding factor is cleaner air. Thus, in Europe, atmospheric brightening due to cleaner air since 1983 has led to higher plant photosynthesis in the spring and summer — and earlier leaf senescence (compared with 1950-1982). These data, however, concern the breakdown of chlorophyll, not the production of red or yellow colors.
Will all kinds of trees respond in the same ways?
Absolutely not. Experimental work is revealing great species-specific differences. For example, trees that have nitrogen-fixing symbionts never turn red or yellow. Both pigments help protect leaves against damage from sunlight that is no longer usable for photosynthesis because of the massive degradation of chloroplast proteins in aging leaves. Trees with steady access to nitrogen may not bother with costly anthocyanin, but instead simply drop their leaves while still relatively green.
Are scientists already seeing changes to the timing or intensity of leaf color changes?
Warmer falls reduce the brilliance of red and yellow leaf colors, but brilliance is hard to quantify in long time series for many species. Also, many species simply do not turn red or yellow.
We have a paper under review that analyzes satellite data on “greenness” in Northern Hemisphere forests. We found that across a large majority of forest areas, higher spring and summer temperatures have led to an earlier (!!!) senescence by, on average, about 1.5 days per degree Celsius. Senescence here refers to degradation of chlorophyll or greenness.
Where in the world are autumn leaves most likely to be affected by climate change?
Species that change leaf color to red or yellow are much more frequent in North America than in Europe. With continued climate warming and lack of frost nights in October, colors will be less brilliant, but the onset or dates of color change will not change much because of the counteracting factors that I mentioned earlier. In the more distant future (after about 2040), and with unmitigated climate change, leaf senescence in Northern Hemisphere trees and shrubs will occur ever earlier.
Source: Washington University in St. Louis
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Author
Last Updated on April 17, 2026 by Daily News Staff
Earth Day is celebrated annually on April 22nd, and it serves as a reminder of the importance of taking care of our planet. It’s a day to reflect on our impact on the environment and to take action to create a better future for our planet.
The first Earth Day was celebrated in 1970, and it marked the beginning of the environmental movement. Since then, Earth Day has grown into an international event, with millions of people around the world participating in activities and events to raise awareness about environmental issues.
One of the main goals of Earth Day is to encourage people to take action to reduce their impact on the environment. This can include simple actions like recycling, conserving energy, and reducing waste. It can also involve more significant actions like advocating for environmental policies and supporting sustainable businesses.
Another important aspect of Earth Day is education. It’s a time to learn about environmental issues and to understand how our actions can impact the planet. Many schools and organizations use Earth Day as an opportunity to teach children about the importance of taking care of the environment.
This year’s Earth Day theme is “Restore Our Earth”, and it focuses on the idea that we can all play a role in restoring the planet’s ecosystems. This can include actions like planting trees, reducing plastic waste, and supporting sustainable agriculture.
Earth Day is an important reminder of the impact that we have on the environment and the importance of taking action to create a better future for our planet. By working together and taking small steps, we can make a big difference in protecting the planet and ensuring that it remains healthy and beautiful for generations to come.
Earth Day – April 22
https://nationaltoday.com/earth-day/
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Author
The Knowledge
Mosquitoes carrying malaria are evolving more quickly than insecticides can kill them – researchers pinpoint how
Jacob A Tennessen, Harvard University
The fight against infectious disease is a race against evolution. Bacteria become resistant to antibiotics. Viruses adapt to spread more quickly. Diseases transmitted by insects present another evolutionary front: Insects themselves can evolve resistance to the poisons that people use to kill them.
In particular, the mosquito-borne disease malaria kills over 600,000 people annually. Since World War II, people have battled malaria with insecticides – chemical weapons intended to kill Anopheles mosquitoes infected with the Plasmodium parasites that cause the disease.
However, mosquitoes are quickly evolving counterstrategies that make these insecticides ineffective, putting millions of people at greater risk of deadly infection. My colleagues and I have newly published research showing how.
Insecticide resistance threatens public health
As an evolutionary geneticist, I study natural selection – the basis for adaptive evolution. Genetic variants that best promote survival can replace less advantageous versions, causing species to change. Anopheles mosquitoes are frustratingly adept at evolving.
In the mid-1990s, most African Anopheles were susceptible to pyrethroids, a popular type of insecticide originally derived from chrysanthemums. Anopheles control relies on two pyrethroid-based methods: insecticide-treated bed nets to protect sleepers, and indoor residual spraying of insecticide against the walls of homes. These two methods alone likely prevented over a half-billion cases of malaria between 2000 and 2015.
However, mosquitoes today from Ghana to Malawi are often able to survive insecticide concentrations 10 times the previously lethal dose. Along with Anopheles control efforts, agriculture also inadvertently exposes mosquitoes to pyrethroids and contributes to insecticide resistance.
In some African locales, Anopheles is already showing resistance to all four main classes of insecticide used for malaria control.
Adaptation in Latin American mosquitoes
Anopheles mosquitoes and the malaria-causing Plasmodium also occur outside Africa, where insecticide resistance is less well-researched.
In much of South America, the main malaria vector is Anopheles darlingi. This mosquito species has diverged evolutionarily from the African vectors so extensively that it might be a different genus, Nyssorhynchus. Along with colleagues from eight countries, I analyzed over 1,000 Anopheles darlingi genomes to understand its genetic diversity, including any recent changes due to human activity. My collaborators collected these mosquitoes at 16 locations ranging from the Atlantic coast of Brazil to the Pacific side of the Andes in Colombia.
We found that, like its African counterparts, Anopheles darlingi shows extremely high genetic diversity – more than 20 times that of humans – indicating that very large populations of this insect exist. A species with such a vast gene pool is well poised to adapt to new challenges. The right mutation giving it the advantage it needs is more likely to pop up when there are so many individuals. And once that mutation starts to spread, it’s protected by numbers since it won’t be wiped out if a few mosquitoes die by chance.
In contrast, bald eagles in the contiguous U.S. were never able to evolve resistance against the insecticide DDT and approached extinction. Evolution is more efficient among millions of insects than mere thousands of birds. And indeed, we saw signals of adaptive evolution in the resistance-related genes of Anopheles darlingi occurring over the past few decades.
Mosquitoes evolve to detoxify poisons
Insecticides like pyrethroids and DDT share the same molecular target: channels in nerve cells that can open and close. When open, the nerve cell stimulates other cells. These insecticides force the channels to remain open and continuously fire, causing paralysis and death. However, insects can evolve resistance by changing the shape of the channel itself.
Earlier genetic scans performed by other researchers had not detected this type of resistance in Anopheles darlingi, and neither did ours. Instead, we found that resistance is evolving in another way: a group of genes encoding enzymes that break down toxic compounds. High activity of these enzymes, called P450, frequently underlies resistance to insecticides in other mosquitoes. The same cluster of P450 genes has changed independently at least seven times across South America since insecticide use began in the mid-20th century.
In French Guiana, a different set of P450 genes exhibits a similar evolutionary pattern, cementing the clear connection between these enzymes and adaptation. Moreover, when we exposed mosquitoes to pyrethroids in sealed bottles, differences among the P450 genes of individual mosquitoes were linked to the length of time they stayed alive.
Insecticide-heavy campaigns against malaria have been only sporadic in South America and may not be the main driver behind this evolution. Instead, it’s possible that mosquitoes are being exposed indirectly to agricultural insecticides. Intriguingly, we saw the strongest signs of evolution in places where farming is prevalent.
Toward more sophisticated vector control
Despite new vaccines and other recent advances against malaria, mosquito control remains essential for reducing disease.
Some countries are launching trials of gene drives to control malaria, which involve forcing a genetic modification into a mosquito population to reduce their numbers or their tolerance for Plasmodium. Such prospects are exciting, though the relentless adaptability of mosquitoes could be an obstacle.
I and others are revising methods to efficiently test for emerging insecticide resistance. Genome-scale sequencing remains important to detect new or unexpected evolutionary responses. The risk of adaptation is highest under a continuous, strong selection pressure, so minimizing, switching and staggering pesticides can help thwart resistance.
Success in the fight against evolving resistance will require a coordinated effort of monitoring, and reacting accordingly. Unlike evolution, humans can think ahead.
Jacob A Tennessen, Research Scientist in Immunology and Infectious Diseases, Harvard University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The science section of our news blog STM Daily News provides readers with captivating and up-to-date information on the latest scientific discoveries, breakthroughs, and innovations across various fields. We offer engaging and accessible content, ensuring that readers with different levels of scientific knowledge can stay informed. Whether it’s exploring advancements in medicine, astronomy, technology, or environmental sciences, our science section strives to shed light on the intriguing world of scientific exploration and its profound impact on our daily lives. From thought-provoking articles to informative interviews with experts in the field, STM Daily News Science offers a harmonious blend of factual reporting, analysis, and exploration, making it a go-to source for science enthusiasts and curious minds alike. https://stmdailynews.com/category/science/
home improvement
Simple Ways to Make At-Home Recycling More Effective
To create a more eco-friendly household, consider these practical tips to help you reduce waste, stay organized and make at-home recycling part of your everyday routine.
Simple Ways to Make At-Home Recycling More Effective
(Feature Impact) Recycling is a simple way households can reduce waste and help protect natural resources. While many communities offer curbside recycling programs, some people still wonder if they’re doing it correctly or if they’re missing opportunities to recycle more.
To create a more eco-friendly household, consider these practical tips to help you reduce waste, stay organized and make recycling part of your everyday routine.
Know What Your Local Program Accepts
Recycling rules vary depending on your city or waste management provider. Most curbside programs include items like cardboard, paper, aluminum cans and plastics, but others – such as glass – may require drop-off recycling. Review your community guidelines so recyclables don’t accidentally end up in the regular trash.
Create a Simple Sorting System
Set up clearly labeled bins – separated for paper, plastics and metals – in a high-traffic area like the kitchen, garage or laundry room.
Rinse Before You Recycle
Food residue can contaminate other recyclables and may cause entire batches of materials to be rejected during the recycling process. Quickly rinsing yogurt cups, jars or soup cans of leftover residue helps keep recycling streams clean and more likely to be processed properly.
Break Down Boxes
Cardboard boxes are among the most commonly recycled household materials. Flattening boxes before placing them in the recycling bin saves space and allows collection trucks to hold more.
Compost Food Scraps
Not everything belongs in the recycling bin, particularly food waste. Composting fruit peels, vegetable scraps, coffee grounds and eggshells is an easy way to reduce the amount of trash your household produces. Finished compost can be used in gardens, flower beds or houseplants, turning kitchen waste into a valuable resource.
Find more ideas for making recycling a natural part of your household routine at eLivingtoday.com.
Photo courtesy of Shutterstock
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