Do objects change colors due to climate change?

With climate change, yesterday's impossible became possible today, making the issue of animals changing color over time a topical topic in the scientific arena. In a report published by the French magazine Nouvel Observateur (L'OBS), writer Jean-Paul Fritz wondered whether global warming had a role in changing the colors of animal fur and bird feathers.

The writer mentioned that this issue raises controversy among scientists, as this problem was first raised a long time ago by the zoologist Constantin Wilhelm Lambert Gloger, who noticed in 1833 that the change of color of birds and mammals occurs more in the tropics.

A century later, and with many researches; A rule called "Gluger" was reached, according to which "the colors of warm-blooded animals, whether fur or feathers, will be darker in environments with increased temperatures and humidity."

Plants and insects

For insects, the problem is how they adapt to rising temperatures; In a study of 473 species of butterflies and dragonflies from Europe, between 1988 and 2006, Dirk Zeus and colleagues from the Philips-University of Marburg in Germany found that these creatures darkened over time.

While its dark colors remained more frequently in the regions located in the far north, and the light colors were distributed in several regions. This is explained by the fact that the structure of insects becomes thinner with the increase in the temperature of the planet, through the process called "natural selection".

The Gloger's rule applies to plants as well; Matthew Kosky and Tia Lynn Ashman from the University of Pittsburgh in the United States have concluded that the color of a part of the Rosacea family, such as the silver geese, has become darker; Depending on its proximity to the equator.

The same theory put forward by these two scientists indicates that flowers resort to darkening the ultraviolet part of their color to protect themselves from strong ultraviolet rays, in the same way that the human body produces large amounts of melanin to protect the skin from the effects of exposure to sunlight.

Melanin percentage

It is the percentage of melanin that determines the color of the skin, whether it is light or dark, and it also determines the color of hair in humans and the colors of fur or feathers in animals, and it has been shown that melanin, in turn, is affected by surrounding conditions and climatic changes as well.

According to ornithologist Caspar Delhi of the German Max Planck Institute, who has analyzed in depth the "Gluger's rule"; The primates that live in areas with high temperature and humidity have a dark dorsal coat, while the gray rats of Asia are darker in areas with heavy rain.

There is disparity and confusion about how to understand the "Gluger rule." In front of that, Caspar Delhi - who has researched dozens of studies on this topic - says, "There is actually a simple rule that says that the color of warm-blooded animals will be darker with higher humidity and temperature."

He added, "The more complex rule states that eumelanin increases with humidity and decreases with low temperatures, while pheomelanin rises in hot and dry areas and decreases rapidly if temperatures drop."

Light and dark

In July 2020, the Journal of Cell Biology published a study by Li Tian of the China University of Geosciences and Michael Benton of the University of Bristol on how plants and animals interact with global warming.

They emphasized that eumelanin and pheomelanin decrease at low temperatures making animals pale, that humidity may be more important than temperature, and that the "Glugger's rule" may also apply to insects.

According to Tian and Benton, "the colors of the organisms are likely to become darker with increased humidity in warm regions." Based on their predictions, as global warming increases, the numbers of dark-colored animals will increase outside the tropics and tropics.

In a related matter, Alexandre Rolland of the Swiss University of Lausanne presented his vision in a study published in the journal Global Change Biology, and it shows that climate change leads to an increase in temperature and ultraviolet rays, and the dark color plays a role in Protect the organism from ultraviolet rays.

As desertification progresses, pale color may spread in some areas, while dark colors spread in areas where increased humidity is expected.

Will we see the change more clearly?

All these theories can be summed up in two sentences: the colors of creatures in warm and humid regions are dark because this provides better camouflage and protection from UV rays; And the colors of organisms in cold regions are also dark because they need sunlight.

The changes that can occur due to global warming are that according to the first theory, the colors of the organisms will be darker, while the second theory states that their colors will become lighter.