Things I Like - Sciences

One of the few things I miss from suburban living is fall foliage. There are 2 blocks on our street that have trees – the rest of our neighborhood is pretty much concrete. So when fall comes, the ‘colors’ are not all that impressive. But we can always wander out to Lincoln or Grant Park to enjoy the beautiful reds, oranges and yellows that arrive this time of year.

Did you know that fall colors are not all that colorful in Europe? Per an article in Live Science, fall foliage in North America and East Asia has a lot of red while autumn leaves in Europe are mostly yellow. Why would this be? Climate differences? Variations in the mineral mix of the soil? Different tree species?

Nope. According to Simcha Lev-Yadun of the University of Haifa-Oranim in Israel and Jarmo Holopainen of the University of Kuopio in Finland, the answer is evolution with the cause being insects and the basic tool being the Ice Age. It seems that the red color in leaves acts as a shield, warding off insects that would eat the leaves if they were yellow.

Until 35 million years ago…large areas of the globe were covered with evergreen jungles or forests composed of tropical trees… During this phase, a series of ice ages and dry spells transpired, and many tree species evolved to become deciduous, dropping their leaves for winter.

Many of these trees also began an evolutionary process of producing red deciduous leaves in order to ward off insects...

In North America, as in East Asia, north-to-south mountain chains enabled plant and animal 'migration' to the south or north with the advance and retreat of the ice according to the climatic fluctuations…along with them migrated their insect ‘enemies’. Thus the war for survival continued there uninterrupted.

In Europe, on the other hand, the mountains… reach from east to west, and therefore no protected areas were created. Many tree species that did not survive the severe cold died, and with them the insects that depended on them for survival.

At the end of the repeated ice ages, most tree species that had survived in Europe had no need to cope with many of the insects that had become extinct, and therefore no longer had to expend efforts on producing red warning leaves.
~ Live Science

An interesting theory although it raises as many questions as it answers, such as – why are yellow leaves more appetizing to insects? Did Lev-Yadun and Holopainen evaluate the color variations between the same tree species in both locations? Does this mean that there are no leaf-eating insects in Europe?

Btw, I liked this not only for the article but for the intelligent comment thread that followed. This is exactly the kind of thing that makes the internet entertaining and useful.

Thanks to Mr. Blogger for passing on the link to this article.

Beautiful Photos:
Top (New England) from cwalker71
Bottom (Borgo San Lorenzo, Italy) from clickykbd