In summer nature feels alive! Everything is vibrant and productive, and the landscape is painted with the diverse colors of every organism and nonliving parts within the ecosystem. Turns out there are many different ways that color is created in nature and there is lots of overlap as well. So what are the causes of color? Let’s get into it!
One of nature’s staples for color are flowers. They are purposefully colorful to attract the eyes of pollinators, and the diversity of color comes from the competition to stand out. The reds, blues, and purples come from anthocyanins which are the same pigments in apples, raspberries, and cherries. Anthocyanins are antioxidants that the plants produce to protect their cells from oxidative stress from the sun, and it has the same effect on us when consumed from food, tea, and even wine! The yellows and orange colors come from carotenoids. In fact, these same pigments are responsible for the fall leaf colors as well.
Sunsets are a part of nature that has inspired awe for as long as people have experienced them. The colors of sunsets are not caused by pigments but instead by the scattering of light as it passes through the atmosphere. The short wavelength blues and violet lights are scattered more often and with less atmosphere to go through. This is why the sky is blue, as it's more difficult for our eyes to perceive the purples. But the long wavelength reds and orange colors require the light to get scattered through a lot of atmosphere in order to be revealed. So This is why we only see these colors during sunrises and sunsets, when the sun sits near the horizon. At this time the light passes through a large amount of atmosphere, scattering the easily formed and dispersed blues and violets and revealing the reds and oranges before it reaches our eyes.
Most people know why plants are green. They are filled with chlorophyll that's used for photosynthesis. But why is chlorophyll green? It turns out that plants only absorb the red and blue wavelengths, meaning that when the green wavelength that is present in all light hits the plants, it is the only wavelength that is reflected back to our eyes. Plants use red light to know where the sun is and adjust their growth to get the most amount of light, and they use blue light to regulate their circadian rhythms. Just like humans!
Another part of nature known for its color are birds. Most times in animals color is used as a means of camouflage, but for many bird species, their colors help them to stand out. Color is used in birds as a sign of health and fitness for both attracting mates and deterring competition. Their color comes from their feathers, but the cause of the color varies by species. Some birds like Cardinals and Goldfinches get their color from yellow carotenoids that they consume from the nuts and seeds in their diets. Red birds like cardinals and house finches convert those yellows to red. Some birds like crows have melanin in their feathers that give them their black color. This is the same pigment in human skin. Melanin also stiffens and strengthens bird feathers which is why many species have black tips at the edges of their wings.
Other birds don’t have pigments in their feathers and instead derive their color from the refraction of light. Some species like hummingbirds have iridescent colors that are caused from the microscopic structure of the feathers refracting many wavelengths differently all at once. Other species like bluebirds and blue jays refract only blue similar to how the blue color in the sky is formed. Some birds are able to see into the ultraviolet range of light, allowing them to have evolved ways to develop variations in their refraction of ultraviolet light. This means that birds have colors that we can’t even see.
Color is an important part of nature. It is created by the reflection and refraction of light, and nature has created many ways to do that. Various pigments in plants have created the vibrant colors we see in the flowers, the scattering of light by particles in the air produces the blue skies and beautiful sunsets, the green color of plants are a side effect of their preference for only red and blue wavelengths, and birds have evolved to use pretty much all of those tricks. So what is the cause of color? It all has to do with our relationship with light, how it behaves, and how we interpret it. And just think, visible light is just a small fraction of the light that exists, so there is a whole collection of light and color we never experience.
Khoo, H. E., Azlan, A., Tang, S. T., & Lim, S. M. (2017). Anthocyanidins and anthocyanins: colored pigments as food, pharmaceutical ingredients, and the potential health benefits. Food & nutrition research, 61(1), 1361779. https://doi.org/10.1080/16546628.2017.1361779
“What A Plant Knows” By Daniel Chamovitz pg 9-26