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Maple Trees Can Protect You From UV Harm

The Crimson King maple tree is known to be one of the best ornamental and shade trees you can have in your yard. Recent research has revealed an interesting facet of this tree — it also offers the highest protection from damaging UV light among trees, with oak and beech following closely.

Maple trees and UV radiation

The study was published in the Urban Forestry & Urban Greening Journal and is the first of its kind to be conducted in the Northern Hemisphere. For the study, researchers looked at 64 specimens from 16 tree species over a period of two summers. While the Crimson King was found to be the most capable of blocking UV light, this does not mean that all maple trees are good at protecting you from ultraviolet light. In fact, a maple tree species called the red maple was discovered to offer the least protection against UV.

During the research period, the team measured the erythemally weighted UV level under a tree canopy. They then compared it with the erythemally weighted UV light of sunlight under normal conditions outdoors. Erythemal weighting helps calculate how damaging UV light exposure is to the skin and whether it will cause conditions like sunburns, skin reddening, and so on. Along with the Crimson King, other trees like hackberry, swamp white oak, and copper beech gave the highest Protection Factor (PF) with a value greater than three, meaning that sitting under the shade of these trees will allow you to remain outside three times longer when compared to not being protected from sunshine. When it came to trees with low PF values, the red maple and maidenhair were in the bottom ranks.

A woman standing outside wearing sunglasses.
Sitting under shade trees with a PF of three will allow you to remain outside three times longer when compared to not being protected from sunshine. (Image: via pixabay / CC0 1.0)

The team also discovered the main factor that makes the difference in UV protection among trees — crown geometry. Those trees that had wider, less transparent crowns provided the highest level of protection. Tree species that have a high level of shade tolerance were also discovered to be far more effective with regard to UV protection. In their paper, the researchers noted that they were surprised that no significant studies have been conducted to identify trees with the highest level of UV protection, since this would have major implications in urban life.

In cities and towns, solar radiation keeps reflecting from hard ground surfaces and building structures, making temperatures hotter. “One way to reduce the effects of UV reflectance is to increase the tree canopy — this is particularly important in urban areas where concrete and other hard surfaces pose heightened UV exposure risks to humans. In-situ measurements indicate that urban trees provide substantial protection against UV. However, few such measurements exist, and variation among tree species have been poorly characterized,” the authors say in the paper, as reported by BBC.

Crimson King maple trees

Crimson King maple trees, also known as Norway maples, can grow up to 45 feet tall and 30 feet wide. You can easily identify Crimson King trees by the color of the leaves, which appear purple to maroon during the months of summer and autumn. During winter, the leaves turn brown in color. The tree was introduced to America in 1756.

The canopy of a Crimson King maple.
Crimson King maple trees are easily identified by the color of the leaves, which appear purple to maroon during the months of summer and autumn. (Image: Screenshot / YouTube)

These trees grow in almost any type of soil, whether it be clayey, sandy, or loamy. Whether the soil is acidic or alkaline in nature does not affect the growth of Crimson King maple trees. The only requirement is that the soil must be drained well. The tree also needs good exposure to sunlight for optimal growth.

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