Why do birches have a white bark?

Question

Several species of the tree genres *Betula* have a white bark,especially when they are young. This is quite peculiar to trees - at least in central Europe; so I'm wondering if there is a ecological reason behind it. The first idea I have is that they protection against the sun. But normally protection of nature against the sun is to make the opposite: put more pigments in the skin, so that the sun does not damage the underlying DNA. If this is the explanation, how do other tree species protect against this?

Answer 1

This is a very interesting question! I was really intrigued by it, so I wanted to look into it. My first thought was that maybe it has something to do with heat. According to this article that I found, this may be the case:

https://northernwoodlands.org/articles/article/why-are-paper-birches-so-white

According to this article, it is possible that the reason birch trees have white bark is to avoid overheating with the change of seasons. Since white means more light is reflected compared to dark trees which absorb more heat, the birch tree may be adapted to cope with high levels of sunlight. I definitely recommend reading through this article if you would like a more thorough explanation.

When it comes to protection of the trees DNA, I was not able to find anything. You pose a very interesting question, and I am curious to know the answer. I spent some time trying to find any information about this topic, but so far I was unsuccessful.